_B_A_S_H(1)                     General Commands Manual                    _B_A_S_H(1)

NNAAMMEE
       bash - GNU Bourne-Again SHell

SSYYNNOOPPSSIISS
       bbaasshh [options] [command_string | file]

CCOOPPYYRRIIGGHHTT
       Bash is Copyright (C) 1989-2024 by the Free Software Foundation, Inc.

DDEESSCCRRIIPPTTIIOONN
       BBaasshh  is  an  sshh-compatible  command language interpreter that executes
       commands read from the standard input or from a file.  BBaasshh also incor-
       porates useful features from the _K_o_r_n and _C shells (kksshh and ccsshh).

       POSIX is the name for a family of computing standards  based  on  Unix.
       BBaasshh  is  intended  to  be a conformant implementation of the Shell and
       Utilities portion  of  the  IEEE  POSIX  specification  (IEEE  Standard
       1003.1).  BBaasshh can be configured to be POSIX-conformant by default.

OOPPTTIIOONNSS
       All of the single-character shell options documented in the description
       of  the  sseett builtin command, including --oo, can be used as options when
       the shell is invoked.  In addition, bbaasshh interprets the  following  op-
       tions when it is invoked:

       --cc        If  the --cc option is present, then commands are read from the
                 first non-option argument _c_o_m_m_a_n_d___s_t_r_i_n_g.  If there are argu-
                 ments after the _c_o_m_m_a_n_d___s_t_r_i_n_g, the  first  argument  is  as-
                 signed  to $$00 and any remaining arguments are assigned to the
                 positional parameters.  The assignment to $$00 sets the name of
                 the shell, which is used in warning and error messages.
       --ii        If the --ii option is present, the shell is _i_n_t_e_r_a_c_t_i_v_e.
       --ll        Make bbaasshh act as if it had been invoked as a login shell (see
                 IINNVVOOCCAATTIIOONN below).
       --rr        If the --rr option is present,  the  shell  becomes  _r_e_s_t_r_i_c_t_e_d
                 (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).
       --ss        If  the --ss option is present, or if no arguments remain after
                 option processing, then commands are read from  the  standard
                 input.   This  option  allows the positional parameters to be
                 set when invoking an interactive shell or when reading  input
                 through a pipe.
       --DD        A  list of all double-quoted strings preceded by $$ is printed
                 on the standard output.  These are the strings that are  sub-
                 ject to language translation when the current locale is not CC
                 or  PPOOSSIIXX.   This  implies the --nn option; no commands will be
                 executed.
       [[--++]]OO [[_s_h_o_p_t___o_p_t_i_o_n]]
                 _s_h_o_p_t___o_p_t_i_o_n is one of the  shell  options  accepted  by  the
                 sshhoopptt   builtin  (see  SSHHEELLLL  BBUUIILLTTIINN  CCOOMMMMAANNDDSS  below).   If
                 _s_h_o_p_t___o_p_t_i_o_n is present, --OO sets the value of that option; ++OO
                 unsets it.  If _s_h_o_p_t___o_p_t_i_o_n is not supplied,  the  names  and
                 values  of the shell options accepted by sshhoopptt are printed on
                 the standard output.  If the invocation  option  is  ++OO,  the
                 output is displayed in a format that may be reused as input.
       ----        A  ----  signals the end of options and disables further option
                 processing.  Any arguments after the  ----  are  treated  as  a
                 shell  script  filename  (see  below) and arguments passed to
                 that script.  An argument of -- is equivalent to ----.

       BBaasshh also interprets a number of multi-character  options.   These  op-
       tions  must  appear on the command line before the single-character op-
       tions to be recognized.

       ----ddeebbuuggggeerr
              Arrange for the debugger profile to be executed before the shell
              starts.  Turns on extended debugging mode (see  the  description
              of the eexxttddeebbuugg option to the sshhoopptt builtin below).
       ----dduummpp--ppoo--ssttrriinnggss
              Equivalent  to  --DD,  but  the  output  is  in the GNU _g_e_t_t_e_x_t ppoo
              (portable object) file format.
       ----dduummpp--ssttrriinnggss
              Equivalent to --DD.
       ----hheellpp Display a usage message on standard  output  and  exit  success-
              fully.
       ----iinniitt--ffiillee _f_i_l_e
       ----rrccffiillee _f_i_l_e
              Execute commands from _f_i_l_e instead of the standard personal ini-
              tialization  file _~_/_._b_a_s_h_r_c if the shell is interactive (see IINN--
              VVOOCCAATTIIOONN below).

       ----llooggiinn
              Equivalent to --ll.

       ----nnooeeddiittiinngg
              Do not use the GNU rreeaaddlliinnee library to read command  lines  when
              the shell is interactive.

       ----nnoopprrooffiillee
              Do  not read either the system-wide startup file _/_e_t_c_/_p_r_o_f_i_l_e or
              any  of  the  personal  initialization  files   _~_/_._b_a_s_h___p_r_o_f_i_l_e,
              _~_/_._b_a_s_h___l_o_g_i_n,  or  _~_/_._p_r_o_f_i_l_e.   By  default,  bbaasshh reads these
              files when it is invoked as a login shell  (see  IINNVVOOCCAATTIIOONN  be-
              low).

       ----nnoorrcc Do  not  read  and  execute  the  personal  initialization  file
              _~_/_._b_a_s_h_r_c if the shell is interactive.  This option is on by de-
              fault if the shell is invoked as sshh.

       ----ppoossiixx
              Change the behavior of bbaasshh where the default operation  differs
              from the POSIX standard to match the standard (_p_o_s_i_x _m_o_d_e).  See
              SSEEEE  AALLSSOO  below  for a reference to a document that details how
              posix mode affects bash's behavior.

       ----rreessttrriicctteedd
              The shell becomes restricted (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).

       ----vveerrbboossee
              Equivalent to --vv.

       ----vveerrssiioonn
              Show version information for this instance of bbaasshh on the  stan-
              dard output and exit successfully.

AARRGGUUMMEENNTTSS
       If arguments remain after option processing, and neither the --cc nor the
       --ss  option  has  been supplied, the first argument is assumed to be the
       name of a file containing shell commands (a _s_h_e_l_l _s_c_r_i_p_t).  If bbaasshh  is
       invoked in this fashion, $$00 is set to the name of the file, and the po-
       sitional parameters are set to the remaining arguments.  BBaasshh reads and
       executes  commands  from  this file, then exits.  BBaasshh's exit status is
       the exit status of the last command executed in the script.  If no com-
       mands are executed, the exit status is 0.  An attempt is first made  to
       open  the file in the current directory, and, if no file is found, then
       the shell searches the directories in PPAATTHH for the script.

IINNVVOOCCAATTIIOONN
       A _l_o_g_i_n _s_h_e_l_l is one whose first character of argument zero is a --,  or
       one started with the ----llooggiinn option.

       An  _i_n_t_e_r_a_c_t_i_v_e  shell is one started without non-option arguments (un-
       less --ss is specified) and without the --cc option, whose  standard  input
       and error are both connected to terminals (as determined by _i_s_a_t_t_y(3)),
       or  one  started  with  the --ii option.  PPSS11 is set and $$-- includes ii if
       bbaasshh is interactive, allowing a shell script or a startup file to  test
       this state.

       The  following paragraphs describe how bbaasshh executes its startup files.
       If any of the files exist but cannot be read, bbaasshh  reports  an  error.
       Tildes  are expanded in filenames as described below under TTiillddee EExxppaann--
       ssiioonn in the EEXXPPAANNSSIIOONN section.

       When bbaasshh is invoked as an interactive login shell, or as a  non-inter-
       active  shell with the ----llooggiinn option, it first reads and executes com-
       mands from the file _/_e_t_c_/_p_r_o_f_i_l_e, if that file exists.   After  reading
       that file, it looks for _~_/_._b_a_s_h___p_r_o_f_i_l_e, _~_/_._b_a_s_h___l_o_g_i_n, and _~_/_._p_r_o_f_i_l_e,
       in  that order, and reads and executes commands from the first one that
       exists and is readable.  The ----nnoopprrooffiillee option may be  used  when  the
       shell is started to inhibit this behavior.

       When an interactive login shell exits, or a non-interactive login shell
       executes  the  eexxiitt  builtin  command, bbaasshh reads and executes commands
       from the file _~_/_._b_a_s_h___l_o_g_o_u_t, if it exists.

       When an interactive shell that is not a login shell  is  started,  bbaasshh
       reads  and executes commands from _~_/_._b_a_s_h_r_c, if that file exists.  This
       may be inhibited by using the ----nnoorrcc option.  The ----rrccffiillee _f_i_l_e  option
       will  force  bbaasshh  to  read  and  execute commands from _f_i_l_e instead of
       _~_/_._b_a_s_h_r_c.

       When bbaasshh is started non-interactively, to run a shell script, for  ex-
       ample,  it  looks for the variable BBAASSHH__EENNVV in the environment, expands
       its value if it appears there, and uses the expanded value as the  name
       of  a  file to read and execute.  BBaasshh behaves as if the following com-
       mand were executed:

              if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi

       but the value of the PPAATTHH variable is not used to search for the  file-
       name.

       If  bbaasshh is invoked with the name sshh, it tries to mimic the startup be-
       havior of historical versions of sshh as closely as possible, while  con-
       forming  to the POSIX standard as well.  When invoked as an interactive
       login shell, or a non-interactive shell with  the  ----llooggiinn  option,  it
       first  attempts  to  read  and  execute  commands from _/_e_t_c_/_p_r_o_f_i_l_e and
       _~_/_._p_r_o_f_i_l_e, in that order.  The ----nnoopprrooffiillee option may be used  to  in-
       hibit  this  behavior.   When  invoked as an interactive shell with the
       name sshh, bbaasshh looks for the variable EENNVV, expands its value  if  it  is
       defined,  and uses the expanded value as the name of a file to read and
       execute.  Since a shell invoked as sshh does not attempt to read and exe-
       cute commands from any other startup files, the ----rrccffiillee option has  no
       effect.   A non-interactive shell invoked with the name sshh does not at-
       tempt to read any other startup files.  When invoked as sshh, bbaasshh enters
       _p_o_s_i_x mode after the startup files are read.

       When bbaasshh is started in _p_o_s_i_x mode, as with the  ----ppoossiixx  command  line
       option, it follows the POSIX standard for startup files.  In this mode,
       interactive  shells  expand  the EENNVV variable and commands are read and
       executed from the file whose name is  the  expanded  value.   No  other
       startup files are read.

       BBaasshh attempts to determine when it is being run with its standard input
       connected  to  a network connection, as when executed by the historical
       remote shell daemon, usually _r_s_h_d, or the secure shell daemon _s_s_h_d.  If
       bbaasshh determines it is being run non-interactively in this  fashion,  it
       reads  and executes commands from _~_/_._b_a_s_h_r_c, if that file exists and is
       readable.  It will not do this if invoked as sshh.  The ----nnoorrcc option may
       be used to inhibit this behavior, and the ----rrccffiillee option may  be  used
       to  force  another file to be read, but neither _r_s_h_d nor _s_s_h_d generally
       invoke the shell with those options or allow them to be specified.

       If the shell is started with the effective user (group) id not equal to
       the real user (group) id, and the --pp option is not supplied, no startup
       files are read, shell functions are not inherited from the environment,
       the SSHHEELLLLOOPPTTSS, BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they  ap-
       pear  in the environment, are ignored, and the effective user id is set
       to the real user id.  If the --pp option is supplied at  invocation,  the
       startup behavior is the same, but the effective user id is not reset.

DDEEFFIINNIITTIIOONNSS
       The  following  definitions  are used throughout the rest of this docu-
       ment.
       bbllaannkk  A space or tab.
       wwoorrdd   A sequence of characters considered as  a  single  unit  by  the
              shell.  Also known as a ttookkeenn.
       nnaammee   A  _w_o_r_d  consisting  only  of alphanumeric characters and under-
              scores, and beginning with an alphabetic character or an  under-
              score.  Also referred to as an iiddeennttiiffiieerr.
       mmeettaacchhaarraacctteerr
              A  character  that,  when unquoted, separates words.  One of the
              following:
              ||  && ;; (( )) << >> ssppaaccee ttaabb nneewwlliinnee
       ccoonnttrrooll ooppeerraattoorr
              A _t_o_k_e_n that performs a control function.  It is one of the fol-
              lowing symbols:
              |||| && &&&& ;; ;;;; ;;&& ;;;;&& (( )) || ||&& <<nneewwlliinnee>>

RREESSEERRVVEEDD WWOORRDDSS
       _R_e_s_e_r_v_e_d _w_o_r_d_s are words that have a special meaning to the shell.  The
       following words are recognized as reserved when unquoted and either the
       first word of a command (see SSHHEELLLL GGRRAAMMMMAARR below), the third word of  a
       ccaassee  or  sseelleecctt command (only iinn is valid), or the third word of a ffoorr
       command (only iinn and ddoo are valid):

       !! ccaassee  ccoopprroocc  ddoo ddoonnee eelliiff eellssee eessaacc ffii ffoorr  ffuunnccttiioonn  iiff  iinn  sseelleecctt
       tthheenn uunnttiill wwhhiillee {{ }} ttiimmee [[[[ ]]]]

SSHHEELLLL GGRRAAMMMMAARR
       This  section  describes  the syntax of the various forms of shell com-
       mands.

   SSiimmppllee CCoommmmaannddss
       A _s_i_m_p_l_e _c_o_m_m_a_n_d is a sequence of optional  variable  assignments  fol-
       lowed  by  bbllaannkk-separated  words and redirections, and terminated by a
       _c_o_n_t_r_o_l _o_p_e_r_a_t_o_r.  The first word specifies the command to be executed,
       and is passed as argument zero.  The remaining words are passed as  ar-
       guments to the invoked command.

       The  return  value  of a _s_i_m_p_l_e _c_o_m_m_a_n_d is its exit status, or 128+_n if
       the command is terminated by signal _n.

   PPiippeelliinneess
       A _p_i_p_e_l_i_n_e is a sequence of one or more commands separated  by  one  of
       the control operators || or ||&&.  The format for a pipeline is:

              [ttiimmee [--pp]] [ ! ] _c_o_m_m_a_n_d_1 [ [|||||&&] _c_o_m_m_a_n_d_2 ... ]

       The standard output of _c_o_m_m_a_n_d_1 is connected via a pipe to the standard
       input  of  _c_o_m_m_a_n_d_2.   This connection is performed before any redirec-
       tions specified by the _c_o_m_m_a_n_d_1(see RREEDDIIRREECCTTIIOONN below).  If ||&& is used,
       _c_o_m_m_a_n_d_1's standard error, in addition to its standard output, is  con-
       nected  to  _c_o_m_m_a_n_d_2's standard input through the pipe; it is shorthand
       for 22>>&&11 ||.  This implicit redirection of the  standard  error  to  the
       standard  output  is performed after any redirections specified by _c_o_m_-
       _m_a_n_d_1.

       The return status of a pipeline is the exit status of the last command,
       unless the ppiippeeffaaiill option is enabled.  If  ppiippeeffaaiill  is  enabled,  the
       pipeline's  return  status is the value of the last (rightmost) command
       to exit with a non-zero status, or zero if all commands  exit  success-
       fully.  If the reserved word !!  precedes a pipeline, the exit status of
       that  pipeline  is the logical negation of the exit status as described
       above.  The shell waits for all commands in the pipeline  to  terminate
       before returning a value.

       If  the  ttiimmee reserved word precedes a pipeline, the elapsed as well as
       user and system time consumed by its execution are  reported  when  the
       pipeline  terminates.   The --pp option changes the output format to that
       specified by POSIX.  When the shell is in _p_o_s_i_x _m_o_d_e, it does not  rec-
       ognize  ttiimmee  as  a  reserved word if the next token begins with a "-".
       The TTIIMMEEFFOORRMMAATT variable may be set to a format  string  that  specifies
       how  the timing information should be displayed; see the description of
       TTIIMMEEFFOORRMMAATT under SShheellll VVaarriiaabblleess below.

       When the shell is in _p_o_s_i_x _m_o_d_e, ttiimmee may be followed by a newline.  In
       this case, the shell displays the total user and system  time  consumed
       by  the  shell and its children.  The TTIIMMEEFFOORRMMAATT variable specifies the
       format of the time information.

       Each command in a multi-command pipeline, where pipes are  created,  is
       executed  in a _s_u_b_s_h_e_l_l, which is a separate process.  See CCOOMMMMAANNDD EEXXEE--
       CCUUTTIIOONN EENNVVIIRROONNMMEENNTT for a description of subshells and a subshell  envi-
       ronment.   If  the  llaassttppiippee  option is enabled using the sshhoopptt builtin
       (see the description of sshhoopptt below), the last element  of  a  pipeline
       may be run by the shell process when job control is not active.

   LLiissttss
       A  _l_i_s_t  is a sequence of one or more pipelines separated by one of the
       operators ;;, &&, &&&&, or ||||, and optionally terminated by one of ;;, &&, or
       <<nneewwlliinnee>>.

       Of these list operators, &&&& and |||| have equal precedence, followed by ;;
       and &&, which have equal precedence.

       A sequence of one or more newlines may appear in a _l_i_s_t  instead  of  a
       semicolon to delimit commands.

       If  a  command  is terminated by the control operator &&, the shell exe-
       cutes the command in the _b_a_c_k_g_r_o_u_n_d in a subshell.  The shell does  not
       wait  for the command to finish, and the return status is 0.  These are
       referred to as _a_s_y_n_c_h_r_o_n_o_u_s commands.  Commands separated by  a  ;;  are
       executed sequentially; the shell waits for each command to terminate in
       turn.   The  return  status is the exit status of the last command exe-
       cuted.

       AND and OR lists are sequences of one or more  pipelines  separated  by
       the  &&&&  and  |||| control operators, respectively.  AND and OR lists are
       executed with left associativity.  An AND list has the form

              _c_o_m_m_a_n_d_1 &&&& _c_o_m_m_a_n_d_2

       _c_o_m_m_a_n_d_2 is executed if, and only if, _c_o_m_m_a_n_d_1 returns an  exit  status
       of zero (success).

       An OR list has the form

              _c_o_m_m_a_n_d_1 |||| _c_o_m_m_a_n_d_2

       _c_o_m_m_a_n_d_2  is executed if, and only if, _c_o_m_m_a_n_d_1 returns a non-zero exit
       status.  The return status of AND and OR lists is the  exit  status  of
       the last command executed in the list.

   CCoommppoouunndd CCoommmmaannddss
       A  _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d is one of the following.  In most cases a _l_i_s_t in a
       command's description may be separated from the rest of the command  by
       one  or  more  newlines, and may be followed by a newline in place of a
       semicolon.

       (_l_i_s_t) _l_i_s_t is executed in a subshell (see CCOOMMMMAANNDD  EEXXEECCUUTTIIOONN  EENNVVIIRROONN--
              MMEENNTT  below for a description of a subshell environment).  Vari-
              able assignments and builtin commands that  affect  the  shell's
              environment do not remain in effect after the command completes.
              The return status is the exit status of _l_i_s_t.

       { _l_i_s_t; }
              _l_i_s_t  is simply executed in the current shell environment.  _l_i_s_t
              must be terminated with a newline or semicolon.  This  is  known
              as  a  _g_r_o_u_p  _c_o_m_m_a_n_d.   The return status is the exit status of
              _l_i_s_t.  Note that unlike the metacharacters (( and )), {{ and }}  are
              _r_e_s_e_r_v_e_d _w_o_r_d_s and must occur where a reserved word is permitted
              to  be  recognized.   Since they do not cause a word break, they
              must be separated from  _l_i_s_t  by  whitespace  or  another  shell
              metacharacter.

       ((_e_x_p_r_e_s_s_i_o_n))
              The _e_x_p_r_e_s_s_i_o_n is evaluated according to the rules described be-
              low under AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN.  If the value of the expression
              is non-zero, the return status is 0; otherwise the return status
              is  1.   The  _e_x_p_r_e_s_s_i_o_n  undergoes the same expansions as if it
              were within double quotes, but double quote  characters  in  _e_x_-
              _p_r_e_s_s_i_o_n are not treated specially and are removed.

       [[[[ _e_x_p_r_e_s_s_i_o_n ]]]]
              Return  a  status  of  0 or 1 depending on the evaluation of the
              conditional expression _e_x_p_r_e_s_s_i_o_n.  Expressions are composed  of
              the  primaries  described  below  under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS.
              The words between the [[[[ and ]]]] do not  undergo  word  splitting
              and pathname expansion.  The shell performs tilde expansion, pa-
              rameter  and  variable  expansion, arithmetic expansion, command
              substitution, process substitution, and quote removal  on  those
              words.   Conditional operators such as --ff must be unquoted to be
              recognized as primaries.

              When used with [[[[, the << and >> operators sort  lexicographically
              using the current locale.

              When  the  ==== and !!== operators are used, the string to the right
              of the operator is considered a pattern and matched according to
              the rules described below under PPaatttteerrnn MMaattcchhiinngg, as if the eexxtt--
              gglloobb shell option were enabled.  The == operator is equivalent to
              ====.  If the nnooccaasseemmaattcchh shell option is enabled,  the  match  is
              performed  without  regard to the case of alphabetic characters.
              The return value is 0 if the string matches  (====)  or  does  not
              match  (!!==)  the pattern, and 1 otherwise.  Any part of the pat-
              tern may be quoted to force the quoted portion to be matched  as
              a string.

              An  additional  binary operator, ==~~, is available, with the same
              precedence as ==== and !!==.  When it is used,  the  string  to  the
              right of the operator is considered a POSIX extended regular ex-
              pression  and  matched  accordingly (using the POSIX _r_e_g_c_o_m_p and
              _r_e_g_e_x_e_c interfaces usually described in _r_e_g_e_x(3)).   The  return
              value  is  0 if the string matches the pattern, and 1 otherwise.
              If the regular expression is syntactically incorrect, the condi-
              tional expression's return value is 2.  If the nnooccaasseemmaattcchh shell
              option is enabled, the match is performed without regard to  the
              case  of  alphabetic  characters.  If any part of the pattern is
              quoted, the quoted portion is  matched  literally.   This  means
              every character in the quoted portion matches itself, instead of
              having  any special pattern matching meaning.  If the pattern is
              stored in a  shell  variable,  quoting  the  variable  expansion
              forces  the  entire  pattern  to  be  matched  literally.  Treat
              bracket expressions in regular expressions carefully, since nor-
              mal quoting and pattern characters lose their  meanings  between
              brackets.

              The  pattern  will  match  if it matches any part of the string.
              Anchor the pattern using the ^^ and $$ regular  expression  opera-
              tors to force it to match the entire string.  The array variable
              BBAASSHH__RREEMMAATTCCHH  records which parts of the string matched the pat-
              tern.  The element of BBAASSHH__RREEMMAATTCCHH with  index  0  contains  the
              portion  of  the  string matching the entire regular expression.
              Substrings matched by parenthesized  subexpressions  within  the
              regular  expression  are saved in the remaining BBAASSHH__RREEMMAATTCCHH in-
              dices. The element of BBAASSHH__RREEMMAATTCCHH with index _n is  the  portion
              of  the  string  matching  the  _nth parenthesized subexpression.
              BBaasshh sets BBAASSHH__RREEMMAATTCCHH in the global scope; declaring  it  as  a
              local variable will lead to unexpected results.

              Expressions  may  be  combined  using  the  following operators,
              listed in decreasing order of precedence:

              (( _e_x_p_r_e_s_s_i_o_n ))
                     Returns the value of _e_x_p_r_e_s_s_i_o_n.  This  may  be  used  to
                     override the normal precedence of operators.
              !! _e_x_p_r_e_s_s_i_o_n
                     True if _e_x_p_r_e_s_s_i_o_n is false.
              _e_x_p_r_e_s_s_i_o_n_1 &&&& _e_x_p_r_e_s_s_i_o_n_2
                     True if both _e_x_p_r_e_s_s_i_o_n_1 and _e_x_p_r_e_s_s_i_o_n_2 are true.
              _e_x_p_r_e_s_s_i_o_n_1 |||| _e_x_p_r_e_s_s_i_o_n_2
                     True if either _e_x_p_r_e_s_s_i_o_n_1 or _e_x_p_r_e_s_s_i_o_n_2 is true.

              The &&&& and |||| operators do not evaluate _e_x_p_r_e_s_s_i_o_n_2 if the value
              of  _e_x_p_r_e_s_s_i_o_n_1  is  sufficient to determine the return value of
              the entire conditional expression.

       ffoorr _n_a_m_e [ [ iinn [ _w_o_r_d _._._. ] ] ; ] ddoo _l_i_s_t ; ddoonnee
              The list of words following iinn is expanded, generating a list of
              items.  The variable _n_a_m_e is set to each element of this list in
              turn, and _l_i_s_t is executed each time.  If the iinn _w_o_r_d  is  omit-
              ted,  the ffoorr command executes _l_i_s_t once for each positional pa-
              rameter that is set (see PPAARRAAMMEETTEERRSS below).  The  return  status
              is  the  exit  status of the last command that executes.  If the
              expansion of the items following iinn results in an empty list, no
              commands are executed, and the return status is 0.

       ffoorr (( _e_x_p_r_1 ; _e_x_p_r_2 ; _e_x_p_r_3 )) ; ddoo _l_i_s_t ; ddoonnee
              First, the arithmetic expression _e_x_p_r_1 is evaluated according to
              the rules described  below  under  AARRIITTHHMMEETTIICC  EEVVAALLUUAATTIIOONN.   The
              arithmetic  expression  _e_x_p_r_2 is then evaluated repeatedly until
              it evaluates to zero.  Each time _e_x_p_r_2 evaluates to  a  non-zero
              value,  _l_i_s_t  is executed and the arithmetic expression _e_x_p_r_3 is
              evaluated.  If any expression is omitted, it behaves  as  if  it
              evaluates to 1.  The return value is the exit status of the last
              command in _l_i_s_t that is executed, or false if any of the expres-
              sions is invalid.

       sseelleecctt _n_a_m_e [ iinn _w_o_r_d ] ; ddoo _l_i_s_t ; ddoonnee
              The list of words following iinn is expanded, generating a list of
              items,  and the set of expanded words is printed on the standard
              error, each preceded by a number.  If the iinn  _w_o_r_d  is  omitted,
              the  positional  parameters  are printed (see PPAARRAAMMEETTEERRSS below).
              sseelleecctt then displays the PPSS33 prompt and reads a  line  from  the
              standard  input.  If the line consists of a number corresponding
              to one of the displayed words, then the value of _n_a_m_e is set  to
              that  word.  If the line is empty, the words and prompt are dis-
              played again.  If EOF is read, the sseelleecctt command completes  and
              returns  1.  Any other value read causes _n_a_m_e to be set to null.
              The line read is saved in the variable RREEPPLLYY.  The _l_i_s_t is  exe-
              cuted  after  each  selection until a bbrreeaakk command is executed.
              The exit status of sseelleecctt is the exit status of the last command
              executed in _l_i_s_t, or zero if no commands were executed.

       ccaassee _w_o_r_d iinn [ [(] _p_a_t_t_e_r_n [ || _p_a_t_t_e_r_n ] ... ) _l_i_s_t ;; ] ... eessaacc
              A ccaassee command first expands _w_o_r_d, and tries to match it against
              each _p_a_t_t_e_r_n in turn, using the matching rules  described  under
              PPaatttteerrnn MMaattcchhiinngg below.  The _w_o_r_d is expanded using tilde expan-
              sion,  parameter  and  variable expansion, arithmetic expansion,
              command substitution, process substitution  and  quote  removal.
              Each _p_a_t_t_e_r_n examined is expanded using tilde expansion, parame-
              ter  and  variable expansion, arithmetic expansion, command sub-
              stitution, process substitution, and quote removal.  If the  nnoo--
              ccaasseemmaattcchh  shell option is enabled, the match is performed with-
              out regard to the case of alphabetic characters.  When  a  match
              is  found, the corresponding _l_i_s_t is executed.  If the ;;;; opera-
              tor is used, no subsequent matches are attempted after the first
              pattern match.  Using ;;&& in place of ;;;; causes execution to con-
              tinue with the _l_i_s_t associated with the next  set  of  patterns.
              Using  ;;;;&& in place of ;;;; causes the shell to test the next pat-
              tern list in the statement, if any, and execute  any  associated
              _l_i_s_t on a successful match, continuing the case statement execu-
              tion as if the pattern list had not matched.  The exit status is
              zero if no pattern matches.  Otherwise, it is the exit status of
              the last command executed in _l_i_s_t.

       iiff _l_i_s_t; tthheenn _l_i_s_t; [ eelliiff _l_i_s_t; tthheenn _l_i_s_t; ] ... [ eellssee _l_i_s_t; ] ffii
              The  iiff  _l_i_s_t is executed.  If its exit status is zero, the tthheenn
              _l_i_s_t is executed.  Otherwise, each  eelliiff  _l_i_s_t  is  executed  in
              turn,  and  if  its  exit status is zero, the corresponding tthheenn
              _l_i_s_t is executed and the command completes.  Otherwise, the eellssee
              _l_i_s_t is executed, if present.  The exit status is the exit  sta-
              tus of the last command executed, or zero if no condition tested
              true.

       wwhhiillee _l_i_s_t_-_1; ddoo _l_i_s_t_-_2; ddoonnee
       uunnttiill _l_i_s_t_-_1; ddoo _l_i_s_t_-_2; ddoonnee
              The  wwhhiillee command continuously executes the list _l_i_s_t_-_2 as long
              as the last command in the list _l_i_s_t_-_1 returns an exit status of
              zero.  The uunnttiill command is identical to the wwhhiillee command,  ex-
              cept that the test is negated: _l_i_s_t_-_2 is executed as long as the
              last command in _l_i_s_t_-_1 returns a non-zero exit status.  The exit
              status of the wwhhiillee and uunnttiill commands is the exit status of the
              last command executed in _l_i_s_t_-_2, or zero if none was executed.

   CCoopprroocceesssseess
       A _c_o_p_r_o_c_e_s_s is a shell command preceded by the ccoopprroocc reserved word.  A
       coprocess  is  executed asynchronously in a subshell, as if the command
       had been terminated with the && control operator, with  a  two-way  pipe
       established between the executing shell and the coprocess.

       The syntax for a coprocess is:

              ccoopprroocc [_N_A_M_E] _c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n_s]

       This  creates  a  coprocess named _N_A_M_E.  _c_o_m_m_a_n_d may be either a simple
       command or a compound command (see above).  _N_A_M_E is  a  shell  variable
       name.  If _N_A_M_E is not supplied, the default name is CCOOPPRROOCC.

       The recommended form to use for a coprocess is

              ccoopprroocc _N_A_M_E { _c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n_s]; }

       This  form  is  recommended  because  simple commands result in the co-
       process always being named CCOOPPRROOCC, and it is simpler to  use  and  more
       complete than the other compound commands.

       If  _c_o_m_m_a_n_d is a compound command, _N_A_M_E is optional. The word following
       ccoopprroocc determines whether that word is interpreted as a variable  name:
       it  is interpreted as _N_A_M_E if it is not a reserved word that introduces
       a compound command.  If _c_o_m_m_a_n_d is a simple command, _N_A_M_E  is  not  al-
       lowed;  this  is  to avoid confusion between _N_A_M_E and the first word of
       the simple command.

       When the coprocess is executed, the shell  creates  an  array  variable
       (see  AArrrraayyss  below)  named _N_A_M_E in the context of the executing shell.
       The standard output of _c_o_m_m_a_n_d is connected via a pipe to  a  file  de-
       scriptor  in  the executing shell, and that file descriptor is assigned
       to _N_A_M_E[0].  The standard input of _c_o_m_m_a_n_d is connected via a pipe to a
       file descriptor in the executing shell, and that file descriptor is as-
       signed to _N_A_M_E[1].  This pipe is established  before  any  redirections
       specified by the command (see RREEDDIIRREECCTTIIOONN below).  The file descriptors
       can  be  utilized as arguments to shell commands and redirections using
       standard word expansions.  Other than those created to execute  command
       and  process  substitutions,  the file descriptors are not available in
       subshells.

       The process ID of the shell spawned to execute the coprocess is  avail-
       able  as  the value of the variable _N_A_M_E_PID.  The wwaaiitt builtin command
       may be used to wait for the coprocess to terminate.

       Since the coprocess is created as an asynchronous command,  the  ccoopprroocc
       command  always  returns  success.  The return status of a coprocess is
       the exit status of _c_o_m_m_a_n_d.

   SShheellll FFuunnccttiioonn DDeeffiinniittiioonnss
       A shell function is an object that is called like a simple command  and
       executes  a  compound  command with a new set of positional parameters.
       Shell functions are declared as follows:

       _f_n_a_m_e () _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n]
       ffuunnccttiioonn _f_n_a_m_e [()] _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n]
              This defines a function named _f_n_a_m_e.  The reserved word ffuunnccttiioonn
              is optional.  If the ffuunnccttiioonn reserved  word  is  supplied,  the
              parentheses  are optional.  The _b_o_d_y of the function is the com-
              pound command _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d (see  CCoommppoouunndd  CCoommmmaannddss  above).
              That  command is usually a _l_i_s_t of commands between { and }, but
              may be any command listed under CCoommppoouunndd CCoommmmaannddss above.  If the
              ffuunnccttiioonn reserved word is used, but the parentheses are not sup-
              plied, the braces are recommended.  _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d is executed
              whenever _f_n_a_m_e is specified as the name  of  a  simple  command.
              When in _p_o_s_i_x _m_o_d_e, _f_n_a_m_e must be a valid shell _n_a_m_e and may not
              be  the  name  of one of the POSIX _s_p_e_c_i_a_l _b_u_i_l_t_i_n_s.  In default
              mode, a function name can be any unquoted shell word  that  does
              not  contain $$.  Any redirections (see RREEDDIIRREECCTTIIOONN below) speci-
              fied when a function is defined are performed when the  function
              is  executed.   The exit status of a function definition is zero
              unless a syntax error occurs or a  readonly  function  with  the
              same  name  already exists.  When executed, the exit status of a
              function is the exit status of the last command executed in  the
              body.  (See FFUUNNCCTTIIOONNSS below.)

CCOOMMMMEENNTTSS
       In a non-interactive shell, or an interactive shell in which the iinntteerr--
       aaccttiivvee__ccoommmmeennttss  option  to  the  sshhoopptt  builtin  is enabled (see SSHHEELLLL
       BBUUIILLTTIINN CCOOMMMMAANNDDSS below), a word beginning with ## causes that  word  and
       all  remaining  characters  on that line to be ignored.  An interactive
       shell without the iinntteerraaccttiivvee__ccoommmmeennttss option enabled  does  not  allow
       comments.  The iinntteerraaccttiivvee__ccoommmmeennttss option is on by default in interac-
       tive shells.

QQUUOOTTIINNGG
       _Q_u_o_t_i_n_g  is used to remove the special meaning of certain characters or
       words to the shell.  Quoting can be used to disable  special  treatment
       for special characters, to prevent reserved words from being recognized
       as such, and to prevent parameter expansion.

       Each  of  the _m_e_t_a_c_h_a_r_a_c_t_e_r_s listed above under DDEEFFIINNIITTIIOONNSS has special
       meaning to the shell and must be quoted if it is to represent itself.

       When the command history expansion facilities are being used (see  HHIISS--
       TTOORRYY EEXXPPAANNSSIIOONN below), the _h_i_s_t_o_r_y _e_x_p_a_n_s_i_o_n character, usually !!, must
       be quoted to prevent history expansion.

       There  are  three  quoting  mechanisms:  the  _e_s_c_a_p_e  _c_h_a_r_a_c_t_e_r, single
       quotes, and double quotes.

       A non-quoted backslash (\\) is the _e_s_c_a_p_e _c_h_a_r_a_c_t_e_r.  It  preserves  the
       literal value of the next character that follows, with the exception of
       <newline>.   If a \\<newline> pair appears, and the backslash is not it-
       self quoted, the \\<newline> is treated as a line continuation (that is,
       it is removed from the input stream and effectively ignored).

       Enclosing characters in single quotes preserves the  literal  value  of
       each character within the quotes.  A single quote may not occur between
       single quotes, even when preceded by a backslash.

       Enclosing  characters  in  double quotes preserves the literal value of
       all characters within the quotes, with the exception of $$, ``,  \\,  and,
       when history expansion is enabled, !!.  When the shell is in _p_o_s_i_x _m_o_d_e,
       the  !!  has  no special meaning within double quotes, even when history
       expansion is enabled.  The characters $$  and  ``  retain  their  special
       meaning  within double quotes.  The backslash retains its special mean-
       ing only when followed by one of the following characters: $$, ``, "",  \\,
       or  <<nneewwlliinnee>>.   A  double  quote may be quoted within double quotes by
       preceding it with a backslash.  If enabled, history expansion  will  be
       performed  unless  an  !!  appearing in double quotes is escaped using a
       backslash.  The backslash preceding the !!  is not removed.

       The special parameters ** and @@ have  special  meaning  when  in  double
       quotes (see PPAARRAAMMEETTEERRSS below).

       Character  sequences  of  the  form  $$'_s_t_r_i_n_g' are treated as a special
       variant of single quotes.  The sequence expands to _s_t_r_i_n_g,  with  back-
       slash-escaped  characters in _s_t_r_i_n_g replaced as specified by the ANSI C
       standard.  Backslash escape sequences, if present, are decoded as  fol-
       lows:
              \\aa     alert (bell)
              \\bb     backspace
              \\ee
              \\EE     an escape character
              \\ff     form feed
              \\nn     new line
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\\\     backslash
              \\''     single quote
              \\""     double quote
              \\??     question mark
              \\_n_n_n   the  eight-bit  character  whose value is the octal value
                     _n_n_n (one to three octal digits)
              \\xx_H_H   the eight-bit character whose value  is  the  hexadecimal
                     value _H_H (one or two hex digits)
              \\uu_H_H_H_H the  Unicode (ISO/IEC 10646) character whose value is the
                     hexadecimal value _H_H_H_H (one to four hex digits)
              \\UU_H_H_H_H_H_H_H_H
                     the Unicode (ISO/IEC 10646) character whose value is  the
                     hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits)
              \\cc_x    a control-_x character

       The  expanded  result  is  single-quoted, as if the dollar sign had not
       been present.

       A double-quoted string preceded by a dollar sign ($$"_s_t_r_i_n_g") will cause
       the string to be translated according to the current locale.  The  _g_e_t_-
       _t_e_x_t  infrastructure  performs  the  lookup  and translation, using the
       LLCC__MMEESSSSAAGGEESS, TTEEXXTTDDOOMMAAIINNDDIIRR, and TTEEXXTTDDOOMMAAIINN  shell  variables.   If  the
       current  locale  is CC or PPOOSSIIXX, if there are no translations available,
       or if the string is not translated, the dollar sign is  ignored.   This
       is a form of double quoting, so the string remains double-quoted by de-
       fault,  whether  or  not  it  is translated and replaced.  If the nnooeexx--
       ppaanndd__ttrraannssllaattiioonn option is enabled using the sshhoopptt builtin,  translated
       strings  are  single-quoted instead of double-quoted.  See the descrip-
       tion of sshhoopptt below under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS.

PPAARRAAMMEETTEERRSS
       A _p_a_r_a_m_e_t_e_r is an entity that stores values.  It can be a _n_a_m_e, a  num-
       ber,  or one of the special characters listed below under SSppeecciiaall PPaarraa--
       mmeetteerrss.  A _v_a_r_i_a_b_l_e is a parameter denoted by a _n_a_m_e.  A variable has a
       _v_a_l_u_e and zero or more _a_t_t_r_i_b_u_t_e_s.  Attributes are assigned  using  the
       ddeeccllaarree builtin command (see ddeeccllaarree below in SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS).

       A parameter is set if it has been assigned a value.  The null string is
       a  valid  value.  Once a variable is set, it may be unset only by using
       the uunnsseett builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

       A _v_a_r_i_a_b_l_e may be assigned to by a statement of the form

              _n_a_m_e=[_v_a_l_u_e]

       If _v_a_l_u_e is not given, the variable is assigned the null  string.   All
       _v_a_l_u_e_s  undergo tilde expansion, parameter and variable expansion, com-
       mand substitution, arithmetic expansion, and quote removal (see  EEXXPPAANN--
       SSIIOONN below).  If the variable has its iinntteeggeerr attribute set, then _v_a_l_u_e
       is evaluated as an arithmetic expression even if the $$((((...)))) expansion
       is not used (see AArriitthhmmeettiicc EExxppaannssiioonn below).  Word splitting and path-
       name  expansion  are not performed.  Assignment statements may also ap-
       pear as arguments to the aalliiaass, ddeeccllaarree, ttyyppeesseett, eexxppoorrtt, rreeaaddoonnllyy, and
       llooccaall builtin commands (_d_e_c_l_a_r_a_t_i_o_n commands).   When  in  _p_o_s_i_x  _m_o_d_e,
       these  builtins  may appear in a command after one or more instances of
       the ccoommmmaanndd builtin and retain these assignment statement properties.

       In the context where an assignment statement is assigning a value to  a
       shell variable or array index, the += operator can be used to append to
       or  add  to  the variable's previous value.  This includes arguments to
       builtin commands such as ddeeccllaarree that accept assignment statements (_d_e_-
       _c_l_a_r_a_t_i_o_n commands).  When += is applied to a variable  for  which  the
       iinntteeggeerr attribute has been set, _v_a_l_u_e is evaluated as an arithmetic ex-
       pression and added to the variable's current value, which is also eval-
       uated.   When += is applied to an array variable using compound assign-
       ment (see AArrrraayyss below), the variable's value is not unset  (as  it  is
       when  using  =),  and new values are appended to the array beginning at
       one greater than the array's maximum  index  (for  indexed  arrays)  or
       added  as additional key-value pairs in an associative array.  When ap-
       plied to a string-valued variable, _v_a_l_u_e is expanded  and  appended  to
       the variable's value.

       A variable can be assigned the _n_a_m_e_r_e_f attribute using the --nn option to
       the  ddeeccllaarree or llooccaall builtin commands (see the descriptions of ddeeccllaarree
       and llooccaall below) to create a _n_a_m_e_r_e_f, or a reference to  another  vari-
       able.   This  allows  variables to be manipulated indirectly.  Whenever
       the nameref variable is referenced, assigned to, unset, or has its  at-
       tributes  modified  (other than using or changing the _n_a_m_e_r_e_f attribute
       itself), the operation is actually performed on the variable  specified
       by  the  nameref  variable's  value.  A nameref is commonly used within
       shell functions to refer to a variable whose name is passed as an argu-
       ment to the function.  For instance, if a variable name is passed to  a
       shell function as its first argument, running

              declare -n ref=$1

       inside  the  function creates a nameref variable rreeff whose value is the
       variable name passed as the first argument.  References and assignments
       to rreeff, and changes to its attributes, are treated as  references,  as-
       signments,  and  attribute modifications to the variable whose name was
       passed as $$11.  If the control variable in a ffoorr loop  has  the  nameref
       attribute,  the  list  of words can be a list of shell variables, and a
       name reference will be established for each word in the list, in  turn,
       when the loop is executed.  Array variables cannot be given the nnaammeerreeff
       attribute.   However,  nameref  variables can reference array variables
       and subscripted array variables.  Namerefs can be unset  using  the  --nn
       option  to the uunnsseett builtin.  Otherwise, if uunnsseett is executed with the
       name of a nameref variable as an argument, the variable  referenced  by
       the nameref variable will be unset.

   PPoossiittiioonnaall PPaarraammeetteerrss
       A  _p_o_s_i_t_i_o_n_a_l  _p_a_r_a_m_e_t_e_r  is a parameter denoted by one or more digits,
       other than the single digit 0.  Positional parameters are assigned from
       the shell's arguments when it is invoked, and may be  reassigned  using
       the  sseett builtin command.  Positional parameters may not be assigned to
       with assignment statements.  The positional parameters are  temporarily
       replaced when a shell function is executed (see FFUUNNCCTTIIOONNSS below).

       When  a  positional parameter consisting of more than a single digit is
       expanded, it must be enclosed in braces (see EEXXPPAANNSSIIOONN below).

   SSppeecciiaall PPaarraammeetteerrss
       The shell treats several parameters specially.   These  parameters  may
       only be referenced; assignment to them is not allowed.
       **      Expands  to  the positional parameters, starting from one.  When
              the expansion is not within double quotes, each positional para-
              meter expands to a separate word.  In contexts where it is  per-
              formed,  those  words  are subject to further word splitting and
              pathname expansion.  When the  expansion  occurs  within  double
              quotes, it expands to a single word with the value of each para-
              meter  separated by the first character of the IIFFSS special vari-
              able.  That is, ""$$**"" is equivalent to ""$$11_c$$22_c......"",  where  _c  is
              the first character of the value of the IIFFSS variable.  If IIFFSS is
              unset,  the parameters are separated by spaces.  If IIFFSS is null,
              the parameters are joined without intervening separators.
       @@      Expands to the positional parameters,  starting  from  one.   In
              contexts  where  word  splitting is performed, this expands each
              positional parameter to a separate word; if  not  within  double
              quotes,  these words are subject to word splitting.  In contexts
              where word splitting is not performed, this expands to a  single
              word  with each positional parameter separated by a space.  When
              the expansion occurs within double quotes,  each  parameter  ex-
              pands  to  a  separate  word.   That  is,  ""$$@@"" is equivalent to
              ""$$11"" ""$$22"" ......  If the double-quoted expansion  occurs  within  a
              word,  the  expansion  of the first parameter is joined with the
              beginning part of the original word, and the  expansion  of  the
              last  parameter  is  joined  with  the last part of the original
              word.  When there are no positional parameters, ""$$@@"" and $$@@  ex-
              pand to nothing (i.e., they are removed).
       ##      Expands to the number of positional parameters in decimal.
       ??      Expands  to  the exit status of the most recently executed fore-
              ground command.
       --      Expands to the current option flags as  specified  upon  invoca-
              tion,  by the sseett builtin command, or those set by the shell it-
              self (such as the --ii option).
       $$      Expands to the process ID of the shell. In a  subshell,  it  ex-
              pands to the process ID of the current shell, not the subshell.
       !!      Expands  to  the process ID of the job most recently placed into
              the background, whether executed as an asynchronous  command  or
              using the bbgg builtin (see JJOOBB CCOONNTTRROOLL below).
       00      Expands  to  the name of the shell or shell script.  This is set
              at shell initialization.  If bbaasshh is invoked with a file of com-
              mands, $$00 is set to the name of that file.  If bbaasshh  is  started
              with  the  --cc option, then $$00 is set to the first argument after
              the string to be executed, if one is present.  Otherwise, it  is
              set  to  the  filename used to invoke bbaasshh, as given by argument
              zero.

   SShheellll VVaarriiaabblleess
       The following variables are set by the shell:

       __      At shell startup, set to the pathname used to invoke  the  shell
              or  shell  script being executed as passed in the environment or
              argument list.  Subsequently, expands to the  last  argument  to
              the  previous  simple  command executed in the foreground, after
              expansion.  Also set to the full pathname used  to  invoke  each
              command  executed and placed in the environment exported to that
              command.  When checking mail, this parameter holds the  name  of
              the mail file currently being checked.
       BBAASSHH   Expands  to  the  full  filename used to invoke this instance of
              bbaasshh.
       BBAASSHHOOPPTTSS
              A colon-separated list of enabled shell options.  Each  word  in
              the  list  is  a  valid  argument for the --ss option to the sshhoopptt
              builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  The options
              appearing in BBAASSHHOOPPTTSS are those reported as  _o_n  by  sshhoopptt.   If
              this  variable  is  in the environment when bbaasshh starts up, each
              shell option in the list will  be  enabled  before  reading  any
              startup files.  This variable is read-only.
       BBAASSHHPPIIDD
              Expands  to  the  process  ID of the current bbaasshh process.  This
              differs from $$$$ under certain circumstances, such  as  subshells
              that  do  not require bbaasshh to be re-initialized.  Assignments to
              BBAASSHHPPIIDD have no effect.  If BBAASSHHPPIIDD is unset, it loses its  spe-
              cial properties, even if it is subsequently reset.
       BBAASSHH__AALLIIAASSEESS
              An  associative  array  variable whose members correspond to the
              internal list of aliases as maintained  by  the  aalliiaass  builtin.
              Elements  added to this array appear in the alias list; however,
              unsetting array elements currently does not cause aliases to  be
              removed from the alias list.  If BBAASSHH__AALLIIAASSEESS is unset, it loses
              its special properties, even if it is subsequently reset.
       BBAASSHH__AARRGGCC
              An  array  variable whose values are the number of parameters in
              each frame of the current bbaasshh execution call stack.  The number
              of parameters to  the  current  subroutine  (shell  function  or
              script  executed  with  .. or ssoouurrccee) is at the top of the stack.
              When a subroutine is executed, the number of  parameters  passed
              is pushed onto BBAASSHH__AARRGGCC.  The shell sets BBAASSHH__AARRGGCC only when in
              extended debugging mode (see the description of the eexxttddeebbuugg op-
              tion  to  the  sshhoopptt builtin below).  Setting eexxttddeebbuugg after the
              shell has started to execute a script, or referencing this vari-
              able when eexxttddeebbuugg is not set, may result in  inconsistent  val-
              ues.  Assignments to BBAASSHH__AARRGGCC have no effect, and it may not be
              unset.
       BBAASSHH__AARRGGVV
              An  array  variable containing all of the parameters in the cur-
              rent bbaasshh execution call stack.  The final parameter of the last
              subroutine call is at the top of the stack; the first  parameter
              of the initial call is at the bottom.  When a subroutine is exe-
              cuted,  the  parameters supplied are pushed onto BBAASSHH__AARRGGVV.  The
              shell sets BBAASSHH__AARRGGVV only when in extended debugging  mode  (see
              the  description of the eexxttddeebbuugg option to the sshhoopptt builtin be-
              low).  Setting eexxttddeebbuugg after the shell has started to execute a
              script, or referencing this variable when eexxttddeebbuugg is  not  set,
              may  result  in  inconsistent  values.  Assignments to BBAASSHH__AARRGGVV
              have no effect, and it may not be unset.
       BBAASSHH__AARRGGVV00
              When referenced, this variable expands to the name of the  shell
              or shell script (identical to $$00; see the description of special
              parameter  0  above).  Assignment to BBAASSHH__AARRGGVV00 causes the value
              assigned to also be assigned to $$00.  If BBAASSHH__AARRGGVV00 is unset,  it
              loses its special properties, even if it is subsequently reset.
       BBAASSHH__CCMMDDSS
              An  associative  array  variable whose members correspond to the
              internal hash table  of  commands  as  maintained  by  the  hhaasshh
              builtin.  Elements added to this array appear in the hash table;
              however,  unsetting array elements currently does not cause com-
              mand names to be removed from the hash table.  If  BBAASSHH__CCMMDDSS  is
              unset,  it  loses  its  special properties, even if it is subse-
              quently reset.
       BBAASSHH__CCOOMMMMAANNDD
              The command currently being executed or about  to  be  executed,
              unless the shell is executing a command as the result of a trap,
              in  which  case  it  is the command executing at the time of the
              trap.  If BBAASSHH__CCOOMMMMAANNDD is unset, it loses  its  special  proper-
              ties, even if it is subsequently reset.
       BBAASSHH__EEXXEECCUUTTIIOONN__SSTTRRIINNGG
              The command argument to the --cc invocation option.
       BBAASSHH__LLIINNEENNOO
              An  array  variable whose members are the line numbers in source
              files where each corresponding member of FFUUNNCCNNAAMMEE  was  invoked.
              $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}}  is  the  line  number  in  the  source  file
              ($${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}})  where  $${{FFUUNNCCNNAAMMEE[[_$_i]]}}  was  called  (or
              $${{BBAASSHH__LLIINNEENNOO[[_$_i_-_1]]}}  if  referenced  within another shell func-
              tion).  Use LLIINNEENNOO to obtain the current line  number.   Assign-
              ments to BBAASSHH__LLIINNEENNOO have no effect, and it may not be unset.
       BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH
              A  colon-separated  list of directories in which the shell looks
              for dynamically loadable builtins specified by the  eennaabbllee  com-
              mand.
       BBAASSHH__RREEMMAATTCCHH
              An  array  variable  whose members are assigned by the ==~~ binary
              operator to the [[[[ conditional command.  The element with  index
              0  is  the portion of the string matching the entire regular ex-
              pression.  The element with index _n is the portion of the string
              matching the _nth parenthesized subexpression.
       BBAASSHH__MMOONNOOSSEECCOONNDDSS
              Each time this variable is referenced, it expands to  the  value
              returned  by  the system's monotonic clock, if one is available.
              If there is no monotonic clock, this is equivalent to  EEPPOOCCHHSSEECC--
              OONNDDSS.   If BBAASSHH__MMOONNOOSSEECCOONNDDSS is unset, it loses its special prop-
              erties, even if it is subsequently reset.
       BBAASSHH__SSOOUURRCCEE
              An array variable whose members are the source  filenames  where
              the  corresponding  shell  function  names in the FFUUNNCCNNAAMMEE array
              variable are defined.  The shell function $${{FFUUNNCCNNAAMMEE[[_$_i]]}} is de-
              fined  in  the   file   $${{BBAASSHH__SSOOUURRCCEE[[_$_i]]}}   and   called   from
              $${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}}.   Assignments  to  BBAASSHH__SSOOUURRCCEE have no ef-
              fect, and it may not be unset.
       BBAASSHH__SSUUBBSSHHEELLLL
              Incremented by one within each subshell or subshell  environment
              when  the  shell begins executing in that environment.  The ini-
              tial value is 0.  If BBAASSHH__SSUUBBSSHHEELLLL is unset, it loses  its  spe-
              cial properties, even if it is subsequently reset.
       BBAASSHH__TTRRAAPPSSIIGG
              Set  to the signal number corresponding to the trap action being
              executed during its execution.  See the description of ttrraapp  un-
              der  SSHHEELLLL  BBUUIILLTTIINN  CCOOMMMMAANNDDSS below for information about signal
              numbers and trap execution.
       BBAASSHH__VVEERRSSIINNFFOO
              A readonly array variable whose members hold version information
              for this instance of bbaasshh.  The values  assigned  to  the  array
              members are as follows:
              BBAASSHH__VVEERRSSIINNFFOO[[0]]        The major version number (the _r_e_l_e_a_s_e).
              BBAASSHH__VVEERRSSIINNFFOO[[1]]        The minor version number (the _v_e_r_s_i_o_n).
              BBAASSHH__VVEERRSSIINNFFOO[[2]]        The patch level.
              BBAASSHH__VVEERRSSIINNFFOO[[3]]        The build version.
              BBAASSHH__VVEERRSSIINNFFOO[[4]]        The release status (e.g., _b_e_t_a).
              BBAASSHH__VVEERRSSIINNFFOO[[5]]        The value of MMAACCHHTTYYPPEE.
       BBAASSHH__VVEERRSSIIOONN
              Expands  to  a string describing the version of this instance of
              bbaasshh.
       CCOOMMPP__CCWWOORRDD
              An index into $${{CCOOMMPP__WWOORRDDSS}} of the word containing  the  current
              cursor position.  This variable is available only in shell func-
              tions  invoked  by  the  programmable completion facilities (see
              PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__KKEEYY
              The key (or final key of a key sequence) used to invoke the cur-
              rent completion function.
       CCOOMMPP__LLIINNEE
              The current command line.  This variable is  available  only  in
              shell  functions and external commands invoked by the programma-
              ble completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__PPOOIINNTT
              The index of the current cursor position relative to the  begin-
              ning  of the current command.  If the current cursor position is
              at the end of the current command, the value of this variable is
              equal to $${{##CCOOMMPP__LLIINNEE}}.  This  variable  is  available  only  in
              shell  functions and external commands invoked by the programma-
              ble completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__TTYYPPEE
              Set to an integer value corresponding to the type of  completion
              attempted  that  caused a completion function to be called: _T_A_B,
              for normal completion, _?, for listing completions after  succes-
              sive  tabs,  _!, for listing alternatives on partial word comple-
              tion, _@, to list completions if the word is not  unmodified,  or
              _%,  for  menu  completion.   This  variable is available only in
              shell functions and external commands invoked by the  programma-
              ble completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__WWOORRDDBBRREEAAKKSS
              The  set  of characters that the rreeaaddlliinnee library treats as word
              separators when performing word completion.  If  CCOOMMPP__WWOORRDDBBRREEAAKKSS
              is  unset, it loses its special properties, even if it is subse-
              quently reset.
       CCOOMMPP__WWOORRDDSS
              An array variable (see AArrrraayyss below) consisting of the  individ-
              ual  words  in the current command line.  The line is split into
              words as rreeaaddlliinnee would split it, using CCOOMMPP__WWOORRDDBBRREEAAKKSS  as  de-
              scribed  above.   This variable is available only in shell func-
              tions invoked by the  programmable  completion  facilities  (see
              PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOPPRROOCC An  array  variable  (see AArrrraayyss below) created to hold the file
              descriptors for output from and input to  an  unnamed  coprocess
              (see CCoopprroocceesssseess above).
       DDIIRRSSTTAACCKK
              An array variable (see AArrrraayyss below) containing the current con-
              tents  of  the directory stack.  Directories appear in the stack
              in the order they are displayed by the ddiirrss builtin.   Assigning
              to members of this array variable may be used to modify directo-
              ries  already in the stack, but the ppuusshhdd and ppooppdd builtins must
              be used to add and remove directories.  Assignment to this vari-
              able will not change the current directory.  If DDIIRRSSTTAACCKK is  un-
              set, it loses its special properties, even if it is subsequently
              reset.
       EEPPOOCCHHRREEAALLTTIIMMEE
              Each time this parameter is referenced, it expands to the number
              of  seconds  since  the  Unix  Epoch (see _t_i_m_e(3)) as a floating
              point  value  with  micro-second  granularity.   Assignments  to
              EEPPOOCCHHRREEAALLTTIIMMEE  are ignored.  If EEPPOOCCHHRREEAALLTTIIMMEE is unset, it loses
              its special properties, even if it is subsequently reset.
       EEPPOOCCHHSSEECCOONNDDSS
              Each time this parameter is referenced, it expands to the number
              of seconds since the Unix Epoch (see _t_i_m_e(3)).   Assignments  to
              EEPPOOCCHHSSEECCOONNDDSS  are  ignored.   If EEPPOOCCHHSSEECCOONNDDSS is unset, it loses
              its special properties, even if it is subsequently reset.
       EEUUIIDD   Expands to the effective user ID of the current  user,  initial-
              ized at shell startup.  This variable is readonly.
       FFUUNNCCNNAAMMEE
              An  array  variable  containing the names of all shell functions
              currently in the execution call stack.  The element with index 0
              is the name of any currently-executing shell function.  The bot-
              tom-most element (the one with the  highest  index)  is  "main".
              This  variable  exists  only when a shell function is executing.
              Assignments to FFUUNNCCNNAAMMEE have no effect.  If FFUUNNCCNNAAMMEE  is  unset,
              it  loses its special properties, even if it is subsequently re-
              set.

              This variable can be  used  with  BBAASSHH__LLIINNEENNOO  and  BBAASSHH__SSOOUURRCCEE.
              Each   element   of   FFUUNNCCNNAAMMEE  has  corresponding  elements  in
              BBAASSHH__LLIINNEENNOO and BBAASSHH__SSOOUURRCCEE to describe the call stack.  For in-
              stance,   $${{FFUUNNCCNNAAMMEE[[_$_i]]}}   was    called    from    the    file
              $${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}}  at  line  number  $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}}.  The
              ccaalllleerr builtin displays the current call stack using this infor-
              mation.
       GGRROOUUPPSS An array variable containing the list of  groups  of  which  the
              current user is a member.  Assignments to GGRROOUUPPSS have no effect.
              If  GGRROOUUPPSS is unset, it loses its special properties, even if it
              is subsequently reset.
       HHIISSTTCCMMDD
              The history number, or index in the history list, of the current
              command.  Assignments to HHIISSTTCCMMDD are ignored.  If HHIISSTTCCMMDD is un-
              set, it loses its special properties, even if it is subsequently
              reset.
       HHOOSSTTNNAAMMEE
              Automatically set to the name of the current host.
       HHOOSSTTTTYYPPEE
              Automatically set to a string that uniquely describes  the  type
              of  machine  on which bbaasshh is executing.  The default is system-
              dependent.
       LLIINNEENNOO Each time this parameter is referenced, the shell substitutes  a
              decimal  number  representing the current sequential line number
              (starting with 1) within a script or function.  When  not  in  a
              script  or  function, the value substituted is not guaranteed to
              be meaningful.  If LLIINNEENNOO is unset, it loses its special proper-
              ties, even if it is subsequently reset.
       MMAACCHHTTYYPPEE
              Automatically set to a string that fully  describes  the  system
              type  on  which  bbaasshh is executing, in the standard GNU _c_p_u_-_c_o_m_-
              _p_a_n_y_-_s_y_s_t_e_m format.  The default is system-dependent.
       MMAAPPFFIILLEE
              An array variable (see AArrrraayyss below) created to  hold  the  text
              read by the mmaappffiillee builtin when no variable name is supplied.
       OOLLDDPPWWDD The previous working directory as set by the ccdd command.
       OOPPTTAARRGG The  value  of the last option argument processed by the ggeettooppttss
              builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       OOPPTTIINNDD The index of the next argument to be processed  by  the  ggeettooppttss
              builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       OOSSTTYYPPEE Automatically  set to a string that describes the operating sys-
              tem on which bbaasshh is executing.  The  default  is  system-depen-
              dent.
       PPIIPPEESSTTAATTUUSS
              An  array  variable (see AArrrraayyss below) containing a list of exit
              status values from the processes in  the  most-recently-executed
              foreground  pipeline, which may consist of only a simple command
              (see SSHHEELLLL GGRRAAMMMMAARR above).
       PPPPIIDD   The process ID of the shell's parent.  This  variable  is  read-
              only.
       PPWWDD    The current working directory as set by the ccdd command.
       RRAANNDDOOMM Each  time  this parameter is referenced, it expands to a random
              integer between 0 and 32767.  Assigning a value to  RRAANNDDOOMM  ini-
              tializes  (seeds)  the sequence of random numbers.  If RRAANNDDOOMM is
              unset, it loses its special properties, even  if  it  is  subse-
              quently reset.
       RREEAADDLLIINNEE__AARRGGUUMMEENNTT
              Any  numeric  argument  given to a readline command that was de-
              fined using "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) when it
              was invoked.
       RREEAADDLLIINNEE__LLIINNEE
              The contents of the rreeaaddlliinnee line buffer, for use with "bind -x"
              (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       RREEAADDLLIINNEE__MMAARRKK
              The position of the mark (saved insertion point) in the rreeaaddlliinnee
              line buffer, for use with "bind -x" (see SSHHEELLLL BBUUIILLTTIINN  CCOOMMMMAANNDDSS
              below).  The characters between the insertion point and the mark
              are often called the _r_e_g_i_o_n.
       RREEAADDLLIINNEE__PPOOIINNTT
              The position of the insertion point in the rreeaaddlliinnee line buffer,
              for use with "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       RREEPPLLYY  Set  to  the line of input read by the rreeaadd builtin command when
              no arguments are supplied.
       SSEECCOONNDDSS
              Each time this parameter is referenced, it expands to the number
              of seconds since shell invocation.  If a value  is  assigned  to
              SSEECCOONNDDSS,  the  value  returned upon subsequent references is the
              number of seconds since the assignment plus the value  assigned.
              The  number  of seconds at shell invocation and the current time
              are always determined by querying the system clock.  If  SSEECCOONNDDSS
              is  unset, it loses its special properties, even if it is subse-
              quently reset.
       SSHHEELLLLOOPPTTSS
              A colon-separated list of enabled shell options.  Each  word  in
              the  list  is  a  valid  argument  for  the --oo option to the sseett
              builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  The options
              appearing in SSHHEELLLLOOPPTTSS are those reported as _o_n by sseett  --oo.   If
              this  variable  is  in the environment when bbaasshh starts up, each
              shell option in the list will  be  enabled  before  reading  any
              startup files.  This variable is read-only.
       SSHHLLVVLL  Incremented by one each time an instance of bbaasshh is started.
       SSRRAANNDDOOMM
              This variable expands to a 32-bit pseudo-random number each time
              it  is  referenced. The random number generator is not linear on
              systems that support _/_d_e_v_/_u_r_a_n_d_o_m or _a_r_c_4_r_a_n_d_o_m(3), so each  re-
              turned  number  has no relationship to the numbers preceding it.
              The random number generator cannot be seeded, so assignments  to
              this variable have no effect.  If SSRRAANNDDOOMM is unset, it loses its
              special properties, even if it is subsequently reset.
       UUIIDD    Expands to the user ID of the current user, initialized at shell
              startup.  This variable is readonly.

       The following variables are used by the shell.  In some cases, bbaasshh as-
       signs a default value to a variable; these cases are noted below.

       BBAASSHH__CCOOMMPPAATT
              The  value  is used to set the shell's compatibility level.  See
              SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below for a description of the  various
              compatibility levels and their effects.  The value may be a dec-
              imal  number  (e.g., 4.2) or an integer (e.g., 42) corresponding
              to the desired compatibility level.  If BBAASSHH__CCOOMMPPAATT is unset  or
              set  to  the empty string, the compatibility level is set to the
              default for the current version.  If BBAASSHH__CCOOMMPPAATT  is  set  to  a
              value  that  is  not  one of the valid compatibility levels, the
              shell prints an error message and sets the  compatibility  level
              to  the  default for the current version.  A subset of the valid
              values correspond to the compatibility  levels  described  below
              under  SSHHEELLLL  CCOOMMPPAATTIIBBIILLIITTYY  MMOODDEE.   For example, 4.2 and 42 are
              valid values that correspond to the ccoommppaatt4422  sshhoopptt  option  and
              set  the compatibility level to 42.  The current version is also
              a valid value.
       BBAASSHH__EENNVV
              If this parameter is set when bbaasshh is executing a shell  script,
              its  value  is  interpreted as a filename containing commands to
              initialize the shell, as in _~_/_._b_a_s_h_r_c.  The value of BBAASSHH__EENNVV is
              subjected to  parameter  expansion,  command  substitution,  and
              arithmetic  expansion  before  being  interpreted as a filename.
              PPAATTHH is not used to search for the resultant filename.
       BBAASSHH__XXTTRRAACCEEFFDD
              If set to an integer corresponding to a valid  file  descriptor,
              bbaasshh  will write the trace output generated when "set -x" is en-
              abled to that file descriptor.  The file  descriptor  is  closed
              when  BBAASSHH__XXTTRRAACCEEFFDD is unset or assigned a new value.  Unsetting
              BBAASSHH__XXTTRRAACCEEFFDD or assigning it the empty string causes the  trace
              output  to  be  sent  to  the standard error.  Note that setting
              BBAASSHH__XXTTRRAACCEEFFDD to 2 (the standard error file descriptor) and then
              unsetting it will result in the standard error being closed.
       CCDDPPAATTHH The search path for the ccdd command.  This is  a  colon-separated
              list of directories in which the shell looks for destination di-
              rectories  specified  by  the  ccdd  command.   A  sample value is
              ".:~:/usr".
       CCHHIILLDD__MMAAXX
              Set the number of exited child status values for  the  shell  to
              remember.   BBaasshh will not allow this value to be decreased below
              a POSIX-mandated minimum, and there is  a  maximum  value  (cur-
              rently  8192)  that  this  may not exceed.  The minimum value is
              system-dependent.
       CCOOLLUUMMNNSS
              Used by the sseelleecctt compound command to  determine  the  terminal
              width  when  printing selection lists.  Automatically set if the
              cchheecckkwwiinnssiizzee option is enabled or in an interactive  shell  upon
              receipt of a SSIIGGWWIINNCCHH.
       CCOOMMPPRREEPPLLYY
              An array variable from which bbaasshh reads the possible completions
              generated  by  a shell function invoked by the programmable com-
              pletion facility (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).  Each  ar-
              ray element contains one possible completion.
       EEMMAACCSS  If  bbaasshh  finds  this variable in the environment when the shell
              starts with value "t", it assumes that the shell is  running  in
              an Emacs shell buffer and disables line editing.
       EENNVV    Expanded  and  executed  similarly  to  BBAASSHH__EENNVV (see IINNVVOOCCAATTIIOONN
              above) when an interactive shell is invoked in _p_o_s_i_x _m_o_d_e.
       EEXXEECCIIGGNNOORREE
              A colon-separated list of shell patterns (see PPaatttteerrnn  MMaattcchhiinngg)
              defining  the  list of filenames to be ignored by command search
              using PPAATTHH.  Files whose full pathnames match one of these  pat-
              terns  are  not  considered executable files for the purposes of
              completion and command execution via PPAATTHH lookup.  This does not
              affect the behavior of the [[, tteesstt, and [[[[ commands.  Full path-
              names in the command hash table are not subject  to  EEXXEECCIIGGNNOORREE.
              Use  this  variable to ignore shared library files that have the
              executable bit set, but are not executable files.   The  pattern
              matching honors the setting of the eexxttgglloobb shell option.
       FFCCEEDDIITT The default editor for the ffcc builtin command.
       FFIIGGNNOORREE
              A  colon-separated  list  of  suffixes to ignore when performing
              filename completion (see RREEAADDLLIINNEE below).  A filename whose suf-
              fix matches one of the entries in FFIIGGNNOORREE is excluded  from  the
              list of matched filenames.  A sample value is ".o:~".
       FFUUNNCCNNEESSTT
              If  set  to  a  numeric  value greater than 0, defines a maximum
              function nesting level.  Function invocations that  exceed  this
              nesting level will cause the current command to abort.
       GGLLOOBBIIGGNNOORREE
              A  colon-separated  list  of  patterns  defining the set of file
              names to be ignored by  pathname  expansion.   If  a  file  name
              matched  by a pathname expansion pattern also matches one of the
              patterns in GGLLOOBBIIGGNNOORREE, it is removed from the list of matches.
       GGLLOOBBSSOORRTT
              Control how the results of pathname expansion are  sorted.   The
              value  of this variable specifies the sort criteria and sort or-
              der for the results of pathname expansion.  If this variable  is
              unset  or  set  to  the null string, pathname expansion uses the
              historical behavior of sorting by name.

              If set, a valid value begins with an optional _+,  which  is  ig-
              nored, or _-, which reverses the sort order from ascending to de-
              scending,  followed  by a sort specifier.  The valid sort speci-
              fiers are _n_a_m_e, _n_u_m_e_r_i_c, _s_i_z_e, _m_t_i_m_e, _a_t_i_m_e, _c_t_i_m_e, and  _b_l_o_c_k_s,
              which sort the files on name, names in numeric rather than lexi-
              cographic  order, file size, modification time, access time, in-
              ode change time, and number of blocks, respectively.  If any  of
              the  non-name  keys compare as equal (e.g., if two files are the
              same size), sorting uses the name as a secondary sort key.   For
              example, a value of _-_m_t_i_m_e sorts the results in descending order
              by modification time (newest first).

              The  _n_u_m_e_r_i_c  specifier treats names consisting solely of digits
              as numbers and sorts them using the numeric value (so  "2"  will
              sort  before "10", for example).  When using _n_u_m_e_r_i_c, names con-
              taining non-digits sort after all the all-digit  names  and  are
              sorted by name using the traditional behavior.

              A  sort specifier of _n_o_s_o_r_t disables sorting completely; the re-
              sults are returned in the order they are read from the file sys-
              tem, and any leading _+ or _- is ignored.  If the  sort  specifier
              is  missing,  it defaults to _n_a_m_e, so a value of _+ is equivalent
              to the null string, and a value of _- sorts by name in descending
              order.  Any invalid value restores the historical sorting behav-
              ior.
       HHIISSTTCCOONNTTRROOLL
              A colon-separated list of values controlling  how  commands  are
              saved  on  the  history  list.   If  the list of values includes
              _i_g_n_o_r_e_s_p_a_c_e, lines which begin with a ssppaaccee  character  are  not
              saved  in  the history list.  A value of _i_g_n_o_r_e_d_u_p_s causes lines
              matching the previous history entry to not be saved.  A value of
              _i_g_n_o_r_e_b_o_t_h is shorthand for _i_g_n_o_r_e_s_p_a_c_e and _i_g_n_o_r_e_d_u_p_s.  A value
              of _e_r_a_s_e_d_u_p_s causes all previous lines matching the current line
              to be removed from the history list before that line  is  saved.
              Any  value  not in the above list is ignored.  If HHIISSTTCCOONNTTRROOLL is
              unset, or does not include a valid value, all lines read by  the
              shell parser are saved on the history list, subject to the value
              of  HHIISSTTIIGGNNOORREE.  The second and subsequent lines of a multi-line
              compound command are not tested, and are added  to  the  history
              regardless of the value of HHIISSTTCCOONNTTRROOLL.
       HHIISSTTFFIILLEE
              The name of the file in which command history is saved (see HHIISS--
              TTOORRYY  below).   BBaasshh assigns a default value of _~_/_._b_a_s_h___h_i_s_t_o_r_y.
              If HHIISSTTFFIILLEE is unset or null, the command history is  not  saved
              when a shell exits.
       HHIISSTTFFIILLEESSIIZZEE
              The maximum number of lines contained in the history file.  When
              this  variable  is  assigned  a value, the history file is trun-
              cated, if necessary, to contain no  more  than  that  number  of
              lines  by removing the oldest entries.  The history file is also
              truncated to this size after writing it when a shell exits.   If
              the  value  is  0,  the  history file is truncated to zero size.
              Non-numeric values and numeric values  less  than  zero  inhibit
              truncation.   The  shell  sets the default value to the value of
              HHIISSTTSSIIZZEE after reading any startup files.
       HHIISSTTIIGGNNOORREE
              A colon-separated list of patterns used to decide which  command
              lines  should  be  saved on the history list.  If a command line
              matches one of the patterns in the value of  HHIISSTTIIGGNNOORREE,  it  is
              not  saved on the history list.  Each pattern is anchored at the
              beginning of the line and must match  the  complete  line  (bbaasshh
              will  not   implicitly  append  a  "**").  Each pattern is tested
              against the line after the checks specified by  HHIISSTTCCOONNTTRROOLL  are
              applied.  In addition to the normal shell pattern matching char-
              acters, "&&" matches the previous history line.  A backslash will
              escape  the  "&&";  the  backslash is removed before attempting a
              match.  The second and subsequent lines of a multi-line compound
              command are not tested, and are added to the history  regardless
              of  the  value  of  HHIISSTTIIGGNNOORREE.  The pattern matching honors the
              setting of the eexxttgglloobb shell option.
       HHIISSTTSSIIZZEE
              The number of commands to remember in the command  history  (see
              HHIISSTTOORRYY  below).   If  the value is 0, commands are not saved in
              the history list.  Numeric values less than zero result in every
              command being saved on the history list  (there  is  no  limit).
              The  shell  sets  the  default  value  to  500 after reading any
              startup files.
       HHIISSTTTTIIMMEEFFOORRMMAATT
              If this variable is set and not null, its value  is  used  as  a
              format string for _s_t_r_f_t_i_m_e(3) to print the time stamp associated
              with  each  history  entry displayed by the hhiissttoorryy builtin.  If
              this variable is set, time stamps are  written  to  the  history
              file  so they may be preserved across shell sessions.  This uses
              the history comment character  to  distinguish  timestamps  from
              other history lines.
       HHOOMMEE   The home directory of the current user; the default argument for
              the ccdd builtin command.  The value of this variable is also used
              when performing tilde expansion.
       HHOOSSTTFFIILLEE
              Contains  the  name  of  a file in the same format as _/_e_t_c_/_h_o_s_t_s
              that should be read when the shell needs to complete a hostname.
              The list of possible hostname completions may be  changed  while
              the  shell  is running; the next time hostname completion is at-
              tempted after the value is changed, bbaasshh adds  the  contents  of
              the  new file to the existing list.  If HHOOSSTTFFIILLEE is set, but has
              no value, or does not name a readable  file,  bbaasshh  attempts  to
              read  _/_e_t_c_/_h_o_s_t_s to obtain the list of possible hostname comple-
              tions.  When HHOOSSTTFFIILLEE is unset, the hostname list is cleared.
       IIFFSS    The _I_n_t_e_r_n_a_l _F_i_e_l_d _S_e_p_a_r_a_t_o_r that is used for word splitting af-
              ter expansion and to  split  lines  into  words  with  the  rreeaadd
              builtin command.  The default value is "<space><tab><newline>".
       IIGGNNOORREEEEOOFF
              Controls the action of an interactive shell on receipt of an EEOOFF
              character as the sole input.  If set, the value is the number of
              consecutive  EEOOFF  characters  which  must  be typed as the first
              characters on an input line before bbaasshh exits.  If the  variable
              exists  but  does not have a numeric value, or has no value, the
              default value is 10.  If it does not exist,  EEOOFF  signifies  the
              end of input to the shell.
       IINNPPUUTTRRCC
              The  filename  for the rreeaaddlliinnee startup file, overriding the de-
              fault of _~_/_._i_n_p_u_t_r_c (see RREEAADDLLIINNEE below).
       IINNSSIIDDEE__EEMMAACCSS
              If this variable appears  in  the  environment  when  the  shell
              starts,  bbaasshh  assumes  that it is running inside an Emacs shell
              buffer and may disable line editing, depending on the  value  of
              TTEERRMM.
       LLAANNGG   Used  to  determine  the  locale  category  for any category not
              specifically selected with a variable starting with LLCC__.
       LLCC__AALLLL This variable overrides the value of  LLAANNGG  and  any  other  LLCC__
              variable specifying a locale category.
       LLCC__CCOOLLLLAATTEE
              This  variable  determines the collation order used when sorting
              the results of pathname expansion, and determines  the  behavior
              of  range  expressions,  equivalence  classes, and collating se-
              quences within pathname expansion and pattern matching.
       LLCC__CCTTYYPPEE
              This variable determines the interpretation  of  characters  and
              the  behavior of character classes within pathname expansion and
              pattern matching.
       LLCC__MMEESSSSAAGGEESS
              This variable determines the locale used  to  translate  double-
              quoted strings preceded by a $$.
       LLCC__NNUUMMEERRIICC
              This  variable  determines  the  locale category used for number
              formatting.
       LLCC__TTIIMMEE
              This variable determines the locale category used for  data  and
              time formatting.
       LLIINNEESS  Used  by  the  sseelleecctt  compound  command to determine the column
              length for printing selection lists.  Automatically set  if  the
              cchheecckkwwiinnssiizzee  option  is enabled or in an interactive shell upon
              receipt of a SSIIGGWWIINNCCHH.
       MMAAIILL   If this parameter is set to a file or  directory  name  and  the
              MMAAIILLPPAATTHH  variable  is not set, bbaasshh informs the user of the ar-
              rival of mail in the specified file or Maildir-format directory.
       MMAAIILLCCHHEECCKK
              Specifies how often (in seconds) bbaasshh checks for mail.  The  de-
              fault  is  60  seconds.   When it is time to check for mail, the
              shell does so before displaying the  primary  prompt.   If  this
              variable  is  unset,  or  set  to  a  value that is not a number
              greater than or equal to zero, the shell disables mail checking.
       MMAAIILLPPAATTHH
              A colon-separated list of filenames to be checked for mail.  The
              message to be printed when mail arrives in a particular file may
              be specified by separating the filename from the message with  a
              "?".   When  used  in the text of the message, $$__ expands to the
              name of the current mailfile.  Example:
              MMAAIILLPPAATTHH='/var/mail/bfox?"You have mail":~/shell-mail?"$_ has mail!"'
              BBaasshh can be configured to supply a default value for this  vari-
              able  (there  is  no  value by default), but the location of the
              user  mail  files  that  it  uses  is  system  dependent  (e.g.,
              /var/mail/$$UUSSEERR).
       OOPPTTEERRRR If set to the value 1, bbaasshh displays error messages generated by
              the  ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
              OOPPTTEERRRR is initialized to 1 each time the shell is invoked  or  a
              shell script is executed.
       PPAATTHH   The  search  path for commands.  It is a colon-separated list of
              directories in which the shell looks for commands  (see  CCOOMMMMAANNDD
              EEXXEECCUUTTIIOONN  below).   A  zero-length (null) directory name in the
              value of PPAATTHH indicates the current directory.  A null directory
              name may appear as two adjacent colons,  or  as  an  initial  or
              trailing  colon.   The  default path is system-dependent, and is
              set by the administrator who installs bbaasshh.  A common value is
              "/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin".
       PPOOSSIIXXLLYY__CCOORRRREECCTT
              If this variable is in the environment  when  bbaasshh  starts,  the
              shell  enters _p_o_s_i_x _m_o_d_e before reading the startup files, as if
              the ----ppoossiixx invocation option had been supplied.  If it  is  set
              while  the  shell is running, bbaasshh enables _p_o_s_i_x _m_o_d_e, as if the
              command "set -o posix" had been executed.  When the shell enters
              _p_o_s_i_x _m_o_d_e, it sets this variable if it was not already set.
       PPRROOMMPPTT__CCOOMMMMAANNDD
              If this variable is set, and is an array, the value of each  set
              element  is  executed as a command prior to issuing each primary
              prompt.  If this is set but not an array variable, its value  is
              used as a command to execute instead.
       PPRROOMMPPTT__DDIIRRTTRRIIMM
              If  set  to a number greater than zero, the value is used as the
              number of trailing directory components to retain when expanding
              the \\ww and \\WW  prompt  string  escapes  (see  PPRROOMMPPTTIINNGG  below).
              Characters removed are replaced with an ellipsis.
       PPSS00    The  value  of  this parameter is expanded (see PPRROOMMPPTTIINNGG below)
              and displayed by interactive shells after reading a command  and
              before the command is executed.
       PPSS11    The  value  of  this parameter is expanded (see PPRROOMMPPTTIINNGG below)
              and used as the primary prompt string.   The  default  value  is
              "\s-\v\$ ".
       PPSS22    The  value of this parameter is expanded as with PPSS11 and used as
              the secondary prompt string.  The default is "> ".
       PPSS33    The value of this parameter is used as the prompt for the sseelleecctt
              command (see SSHHEELLLL GGRRAAMMMMAARR above).
       PPSS44    The value of this parameter is expanded  as  with  PPSS11  and  the
              value is printed before each command bbaasshh displays during an ex-
              ecution trace.  The first character of the expanded value of PPSS44
              is replicated multiple times, as necessary, to indicate multiple
              levels of indirection.  The default is "+ ".
       SSHHEELLLL  This  variable expands to the full pathname to the shell.  If it
              is not set when the shell starts, bbaasshh assigns to  it  the  full
              pathname of the current user's login shell.
       TTIIMMEEFFOORRMMAATT
              The  value of this parameter is used as a format string specify-
              ing how the timing information for pipelines prefixed  with  the
              ttiimmee  reserved word should be displayed.  The %% character intro-
              duces an escape sequence that is expanded to  a  time  value  or
              other  information.  The escape sequences and their meanings are
              as follows; the brackets denote optional portions.
              %%%%        A literal %%.
              %%[[_p]][[ll]]RR  The elapsed time in seconds.
              %%[[_p]][[ll]]UU  The number of CPU seconds spent in user mode.
              %%[[_p]][[ll]]SS  The number of CPU seconds spent in system mode.
              %%PP        The CPU percentage, computed as (%U + %S) / %R.

              The optional _p is a digit specifying the _p_r_e_c_i_s_i_o_n,  the  number
              of fractional digits after a decimal point.  A value of 0 causes
              no  decimal  point or fraction to be output.  At most six places
              after the decimal point may be specified; values  of  _p  greater
              than  6 are changed to 6.  If _p is not specified, the value 3 is
              used.

              The optional ll specifies a longer format, including minutes,  of
              the  form  _M_Mm_S_S._F_Fs.   The value of _p determines whether or not
              the fraction is included.

              If this variable is not set, bbaasshh acts as if it  had  the  value
              $$''\\nnrreeaall\\tt%%33llRR\\nnuusseerr\\tt%%33llUU\\nnssyyss\\tt%%33llSS''.   If  the value is null,
              bbaasshh does not display any timing information.  A  trailing  new-
              line is added when the format string is displayed.
       TTMMOOUUTT  If set to a value greater than zero, TTMMOOUUTT is treated as the de-
              fault  timeout  for the rreeaadd builtin.  The sseelleecctt command termi-
              nates if input does not arrive after TTMMOOUUTT seconds when input is
              coming from a terminal.  In an interactive shell, the  value  is
              interpreted as the number of seconds to wait for a line of input
              after issuing the primary prompt.  BBaasshh terminates after waiting
              for  that number of seconds if a complete line of input does not
              arrive.
       TTMMPPDDIIRR If set, bbaasshh uses its value as the name of a directory in  which
              bbaasshh creates temporary files for the shell's use.
       aauuttoo__rreessuummee
              This variable controls how the shell interacts with the user and
              job  control.   If this variable is set, single word simple com-
              mands without redirections are treated as candidates for resump-
              tion of an existing stopped job.  There is no ambiguity allowed;
              if there is more than one job beginning with the  string  typed,
              the  job  most  recently  accessed  is  selected.  The _n_a_m_e of a
              stopped job, in this context, is the command line used to  start
              it.   If  set to the value _e_x_a_c_t, the string supplied must match
              the name of a stopped job exactly;  if  set  to  _s_u_b_s_t_r_i_n_g,  the
              string  supplied  needs  to  match  a substring of the name of a
              stopped job.  The _s_u_b_s_t_r_i_n_g value provides functionality  analo-
              gous  to the %%??  job identifier (see JJOOBB CCOONNTTRROOLL below).  If set
              to any other value, the supplied string must be a  prefix  of  a
              stopped job's name; this provides functionality analogous to the
              %%_s_t_r_i_n_g job identifier.
       hhiissttcchhaarrss
              The  two or three characters which control history expansion and
              tokenization (see HHIISSTTOORRYY EEXXPPAANNSSIIOONN below).  The first character
              is the _h_i_s_t_o_r_y _e_x_p_a_n_s_i_o_n character, the character which  signals
              the  start  of  a  history  expansion, normally "!!".  The second
              character is the _q_u_i_c_k _s_u_b_s_t_i_t_u_t_i_o_n character, which is used  as
              shorthand  for  re-running the previous command entered, substi-
              tuting one string for another in the command, when it appears as
              the first character on the line.  The default is "^^".   The  op-
              tional third character is the character which indicates that the
              remainder of the line is a comment when found as the first char-
              acter  of  a  word, normally "##".  The history comment character
              causes history substitution to  be  skipped  for  the  remaining
              words  on  the  line.   It  does not necessarily cause the shell
              parser to treat the rest of the line as a comment.

   AArrrraayyss
       BBaasshh provides one-dimensional indexed and associative array  variables.
       Any  variable may be used as an indexed array; the ddeeccllaarree builtin will
       explicitly declare an array.  There is no maximum limit on the size  of
       an  array, nor any requirement that members be indexed or assigned con-
       tiguously.  Indexed arrays are  referenced  using  integers  (including
       arithmetic expressions) and are zero-based; associative arrays are ref-
       erenced using arbitrary strings.  Unless otherwise noted, indexed array
       indices must be non-negative integers.

       An  indexed  array is created automatically if any variable is assigned
       to using the syntax _n_a_m_e[_s_u_b_s_c_r_i_p_t]=_v_a_l_u_e.  The _s_u_b_s_c_r_i_p_t is treated as
       an arithmetic expression that must evaluate to a number.  To explicitly
       declare an indexed array, use ddeeccllaarree --aa _n_a_m_e (see SSHHEELLLL  BBUUIILLTTIINN  CCOOMM--
       MMAANNDDSS  below).   ddeeccllaarree  --aa _n_a_m_e[[_s_u_b_s_c_r_i_p_t]] is also accepted; the _s_u_b_-
       _s_c_r_i_p_t is ignored.

       Associative arrays are created using ddeeccllaarree --AA _n_a_m_e.

       Attributes may be specified for an array variable using the ddeeccllaarree and
       rreeaaddoonnllyy builtins.  Each attribute applies to all members of an array.

       Arrays  are  assigned  to  using  compound  assignments  of  the   form
       _n_a_m_e=((value_1  ...  value_n)),  where  each _v_a_l_u_e may be of the form [_s_u_b_-
       _s_c_r_i_p_t]=_s_t_r_i_n_g.  Indexed array assignments do not require anything  but
       _s_t_r_i_n_g.   Each _v_a_l_u_e in the list is expanded using the shell expansions
       described below under EEXXPPAANNSSIIOONN, but _v_a_l_u_es that are valid variable as-
       signments including the brackets and subscript do not undergo brace ex-
       pansion and word splitting, as with  individual  variable  assignments.
       When  assigning  to  indexed  arrays, if the optional brackets and sub-
       script are supplied, that index is assigned to; otherwise the index  of
       the  element  assigned  is  the last index assigned to by the statement
       plus one.  Indexing starts at zero.

       When assigning to an associative array, the words in a compound assign-
       ment may be either assignment statements, for which  the  subscript  is
       required,  or  a list of words that is interpreted as a sequence of al-
       ternating keys and values: _n_a_m_e=(( _k_e_y_1 _v_a_l_u_e_1 _k_e_y_2 _v_a_l_u_e_2 ...)).   These
       are  treated  identically  to  _n_a_m_e=(( [_k_e_y_1]=_v_a_l_u_e_1 [_k_e_y_2]=_v_a_l_u_e_2 ...)).
       The first word in the list determines how the remaining words  are  in-
       terpreted;  all  assignments  in a list must be of the same type.  When
       using key/value pairs, the keys may not be missing or  empty;  a  final
       missing value is treated like the empty string.

       This  syntax is also accepted by the ddeeccllaarree builtin.  Individual array
       elements may be assigned to using the _n_a_m_e[_s_u_b_s_c_r_i_p_t]=_v_a_l_u_e syntax  in-
       troduced  above.   When  assigning to an indexed array, if _n_a_m_e is sub-
       scripted by a negative number, that number is interpreted  as  relative
       to  one  greater  than  the  maximum index of _n_a_m_e, so negative indices
       count back from the end of the array, and an index of -1 references the
       last element.

       The += operator will append to an array variable when  assigning  using
       the compound assignment syntax; see PPAARRAAMMEETTEERRSS above.

       Any  element  of  an  array may be referenced using ${_n_a_m_e[_s_u_b_s_c_r_i_p_t]}.
       The braces are required to avoid conflicts with pathname expansion.  If
       _s_u_b_s_c_r_i_p_t is @@ or **, the word expands to all members  of  _n_a_m_e,  unless
       noted  in  the  description of a builtin or word expansion.  These sub-
       scripts differ only when the word appears within double quotes.  If the
       word is double-quoted, ${_n_a_m_e[*]} expands to a  single  word  with  the
       value  of each array member separated by the first character of the IIFFSS
       special variable, and ${_n_a_m_e[@]} expands each element of _n_a_m_e to a sep-
       arate word.  When there are no array  members,  ${_n_a_m_e[@]}  expands  to
       nothing.   If the double-quoted expansion occurs within a word, the ex-
       pansion of the first parameter is joined with the beginning part of the
       original word, and the expansion of the last parameter is  joined  with
       the last part of the original word.  This is analogous to the expansion
       of  the  special  parameters  **  and  @@ (see SSppeecciiaall PPaarraammeetteerrss above).
       ${#_n_a_m_e[_s_u_b_s_c_r_i_p_t]} expands to the length  of  ${_n_a_m_e[_s_u_b_s_c_r_i_p_t]}.   If
       _s_u_b_s_c_r_i_p_t is ** or @@, the expansion is the number of elements in the ar-
       ray.  If the _s_u_b_s_c_r_i_p_t used to reference an element of an indexed array
       evaluates  to a number less than zero, it is interpreted as relative to
       one greater than the maximum index of the array,  so  negative  indices
       count back from the end of the array, and an index of -1 references the
       last element.

       Referencing an array variable without a subscript is equivalent to ref-
       erencing  the array with a subscript of 0.  Any reference to a variable
       using a valid subscript is valid, and bbaasshh will create an array if nec-
       essary.

       An array variable is considered set if a subscript has been assigned  a
       value.  The null string is a valid value.

       It  is possible to obtain the keys (indices) of an array as well as the
       values.  ${!!_n_a_m_e[_@]} and ${!!_n_a_m_e[_*]} expand to the indices assigned  in
       array variable _n_a_m_e.  The treatment when in double quotes is similar to
       the expansion of the special parameters _@ and _* within double quotes.

       The uunnsseett builtin is used to destroy arrays.  uunnsseett _n_a_m_e[_s_u_b_s_c_r_i_p_t] de-
       stroys the array element at index _s_u_b_s_c_r_i_p_t, for both indexed and asso-
       ciative  arrays.  Negative subscripts to indexed arrays are interpreted
       as described above.  Unsetting the last element of  an  array  variable
       does  not  unset the variable.  uunnsseett _n_a_m_e, where _n_a_m_e is an array, re-
       moves the entire array.  uunnsseett _n_a_m_e[_s_u_b_s_c_r_i_p_t], where _s_u_b_s_c_r_i_p_t is ** or
       @@, behaves differently depending on whether _n_a_m_e is an indexed or asso-
       ciative array.  If _n_a_m_e is an associative array, this unsets  the  ele-
       ment with subscript ** or @@.  If _n_a_m_e is an indexed array, unset removes
       all of the elements but does not remove the array itself.

       When  using  a  variable name with a subscript as an argument to a com-
       mand, such as with uunnsseett, without using the word expansion  syntax  de-
       scribed above, the argument is subject to pathname expansion.  If path-
       name expansion is not desired, the argument should be quoted.

       The  ddeeccllaarree,  llooccaall,  and rreeaaddoonnllyy builtins each accept a --aa option to
       specify an indexed array and a --AA option to specify an associative  ar-
       ray.   If  both  options  are  supplied, --AA takes precedence.  The rreeaadd
       builtin accepts a --aa option to assign a list of  words  read  from  the
       standard input to an array.  The sseett and ddeeccllaarree builtins display array
       values in a way that allows them to be reused as assignments.

EEXXPPAANNSSIIOONN
       Expansion is performed on the command line after it has been split into
       words.  The shell performs these expansions: _b_r_a_c_e _e_x_p_a_n_s_i_o_n, _t_i_l_d_e _e_x_-
       _p_a_n_s_i_o_n, _p_a_r_a_m_e_t_e_r _a_n_d _v_a_r_i_a_b_l_e _e_x_p_a_n_s_i_o_n, _c_o_m_m_a_n_d _s_u_b_s_t_i_t_u_t_i_o_n, _a_r_i_t_h_-
       _m_e_t_i_c _e_x_p_a_n_s_i_o_n, _w_o_r_d _s_p_l_i_t_t_i_n_g, _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n, and _q_u_o_t_e _r_e_m_o_v_a_l.

       The order of expansions is: brace expansion; tilde expansion, parameter
       and  variable expansion, arithmetic expansion, and command substitution
       (done in a left-to-right fashion); word splitting; pathname  expansion;
       and quote removal.

       On systems that can support it, there is an additional expansion avail-
       able:  _p_r_o_c_e_s_s  _s_u_b_s_t_i_t_u_t_i_o_n.   This  is  performed at the same time as
       tilde, parameter, variable, and arithmetic expansion and  command  sub-
       stitution.

       _Q_u_o_t_e  _r_e_m_o_v_a_l  is  always performed last.  It removes quote characters
       present in the original word, not ones resulting from one of the  other
       expansions, unless they have been quoted themselves.

       Only  brace  expansion,  word splitting, and pathname expansion can in-
       crease the number of words of the expansion; other expansions expand  a
       single  word to a single word.  The only exceptions to this are the ex-
       pansions  of  ""$$@@""  and  ""$${{_n_a_m_e[[@@]]}}"",  and,  in  most  cases,  $$**  and
       $${{_n_a_m_e[[**]]}} as explained above (see PPAARRAAMMEETTEERRSS).

   BBrraaccee EExxppaannssiioonn
       _B_r_a_c_e _e_x_p_a_n_s_i_o_n is a mechanism by which arbitrary strings may be gener-
       ated.   This  mechanism is similar to _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n, but the file-
       names generated need not exist.  Patterns to be brace expanded take the
       form of an optional _p_r_e_a_m_b_l_e, followed by either a series of comma-sep-
       arated strings or a sequence expression between a pair of braces,  fol-
       lowed  by  an  optional  _p_o_s_t_s_c_r_i_p_t.   The preamble is prefixed to each
       string contained within the braces, and the postscript is then appended
       to each resulting string, expanding left to right.

       Brace expansions may be nested.  The results of  each  expanded  string
       are  not  sorted;  left  to  right  order  is  preserved.  For example,
       a{{d,c,b}}e expands into "ade ace abe".

       A sequence expression takes the form {{_x...._y[[...._i_n_c_r]]}}, where _x and _y  are
       either  integers or single letters, and _i_n_c_r, an optional increment, is
       an integer.  When integers are supplied, the expression expands to each
       number between _x and _y, inclusive.  If the supplied integers  are  pre-
       fixed  with _0, each term will have the same width, zero-padding if nec-
       essary.  When either _x or _y begins with a zero, the shell  attempts  to
       force  all  generated terms to contain the same number of digits, zero-
       padding where necessary.  When letters are supplied, the expression ex-
       pands to each character lexicographically between _x and  _y,  inclusive,
       using the default C locale.  Note that both _x and _y must be of the same
       type  (integer  or letter).  When the increment is supplied, it is used
       as the difference between each term.  The default increment is 1 or  -1
       as appropriate.

       Brace expansion is performed before any other expansions, and any char-
       acters  special to other expansions are preserved in the result.  It is
       strictly textual.  BBaasshh does not apply any syntactic interpretation  to
       the context of the expansion or the text between the braces.

       A  correctly-formed  brace  expansion must contain unquoted opening and
       closing braces, and at least one unquoted comma or a valid sequence ex-
       pression.  Any incorrectly formed brace expansion is left unchanged.  A
       {{ or ,, may be quoted with a backslash to prevent its  being  considered
       part  of  a brace expression.  To avoid conflicts with parameter expan-
       sion, the string $${{ is not considered eligible for brace expansion, and
       inhibits brace expansion until the closing }}.

       This construct is typically used as shorthand when the common prefix of
       the strings to be generated is longer than in the above example:

              mkdir /usr/local/src/bash/{old,new,dist,bugs}
       or
              chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}

       Brace expansion introduces a  slight  incompatibility  with  historical
       versions  of sshh.  sshh does not treat opening or closing braces specially
       when they appear as part of a word, and preserves them in  the  output.
       BBaasshh  removes  braces  from  words as a consequence of brace expansion.
       For example, a word entered to sshh as _f_i_l_e_{_1_,_2_} appears  identically  in
       the  output.  The same word is output as _f_i_l_e_1 _f_i_l_e_2 after expansion by
       bbaasshh.  If strict compatibility with sshh is desired, start bbaasshh with  the
       ++BB option or disable brace expansion with the ++BB option to the sseett com-
       mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

   TTiillddee EExxppaannssiioonn
       If  a  word  begins  with an unquoted tilde character ("~~"), all of the
       characters preceding the first unquoted slash (or  all  characters,  if
       there  is no unquoted slash) are considered a _t_i_l_d_e_-_p_r_e_f_i_x.  If none of
       the characters in the tilde-prefix are quoted, the  characters  in  the
       tilde-prefix  following the tilde are treated as a possible _l_o_g_i_n _n_a_m_e.
       If this login name is the null string, the tilde is replaced  with  the
       value  of  the shell parameter HHOOMMEE.  If HHOOMMEE is unset, the home direc-
       tory of the user executing the shell is  substituted  instead.   Other-
       wise,  the  tilde-prefix is replaced with the home directory associated
       with the specified login name.

       If the tilde-prefix is a "~+", the value of the shell variable PPWWDD  re-
       places  the  tilde-prefix.  If the tilde-prefix is a "~-", the value of
       the shell variable OOLLDDPPWWDD, if it is set, is substituted.  If the  char-
       acters  following  the tilde in the tilde-prefix consist of a number _N,
       optionally prefixed by a "+" or a "-",  the  tilde-prefix  is  replaced
       with the corresponding element from the directory stack, as it would be
       displayed by the ddiirrss builtin invoked with the tilde-prefix as an argu-
       ment.   If  the characters following the tilde in the tilde-prefix con-
       sist of a number without a leading "+" or "-", "+" is assumed.

       If the login name is invalid, or the tilde expansion fails, the word is
       unchanged.

       Each variable assignment is checked for unquoted tilde-prefixes immedi-
       ately following a :: or the first ==.  In these cases, tilde expansion is
       also performed.  Consequently, one may use filenames with tildes in as-
       signments to PPAATTHH, MMAAIILLPPAATTHH, and CCDDPPAATTHH, and the shell assigns the  ex-
       panded value.

       BBaasshh  also  performs tilde expansion on words satisfying the conditions
       of variable assignments (as described above under PPAARRAAMMEETTEERRSS) when they
       appear as arguments to simple commands.  BBaasshh does not do this,  except
       for the _d_e_c_l_a_r_a_t_i_o_n commands listed above, when in _p_o_s_i_x _m_o_d_e.

   PPaarraammeetteerr EExxppaannssiioonn
       The "$$" character introduces parameter expansion, command substitution,
       or  arithmetic  expansion.  The parameter name or symbol to be expanded
       may be enclosed in braces, which are optional but serve to protect  the
       variable  to be expanded from characters immediately following it which
       could be interpreted as part of the name.

       When braces are used, the matching ending brace is the  first  "}}"  not
       escaped by a backslash or within a quoted string, and not within an em-
       bedded  arithmetic expansion, command substitution, or parameter expan-
       sion.

       ${_p_a_r_a_m_e_t_e_r}
              The value of _p_a_r_a_m_e_t_e_r is substituted.  The braces are  required
              when  _p_a_r_a_m_e_t_e_r  is  a  positional  parameter with more than one
              digit, or when _p_a_r_a_m_e_t_e_r is followed by a character which is not
              to be interpreted as part of its name.  The _p_a_r_a_m_e_t_e_r is a shell
              parameter as described above PPAARRAAMMEETTEERRSS) or an  array  reference
              (AArrrraayyss).

       If  the  first  character of _p_a_r_a_m_e_t_e_r is an exclamation point (!!), and
       _p_a_r_a_m_e_t_e_r is not a _n_a_m_e_r_e_f, it introduces a level of indirection.  BBaasshh
       uses the value formed by expanding the rest of _p_a_r_a_m_e_t_e_r as the new _p_a_-
       _r_a_m_e_t_e_r; this is then expanded and that value is used in  the  rest  of
       the  expansion,  rather  than  the expansion of the original _p_a_r_a_m_e_t_e_r.
       This is known as _i_n_d_i_r_e_c_t _e_x_p_a_n_s_i_o_n.  The value is subject to tilde ex-
       pansion, parameter expansion, command substitution, and arithmetic  ex-
       pansion.   If  _p_a_r_a_m_e_t_e_r  is a nameref, this expands to the name of the
       parameter referenced by _p_a_r_a_m_e_t_e_r instead of  performing  the  complete
       indirect  expansion.   The  exceptions  to  this  are the expansions of
       ${!!_p_r_e_f_i_x**} and ${!!_n_a_m_e[_@]} described  below.   The  exclamation  point
       must  immediately  follow the left brace in order to introduce indirec-
       tion.

       In each of the cases below, _w_o_r_d is subject to tilde expansion, parame-
       ter expansion, command substitution, and arithmetic expansion.

       When not performing substring expansion, using the forms documented be-
       low (e.g., ::--), bbaasshh tests for a  parameter  that  is  unset  or  null.
       Omitting  the  colon results in a test only for a parameter that is un-
       set.

       ${_p_a_r_a_m_e_t_e_r::--_w_o_r_d}
              UUssee DDeeffaauulltt VVaalluueess.  If _p_a_r_a_m_e_t_e_r is unset or null,  the  expan-
              sion  of _w_o_r_d is substituted.  Otherwise, the value of _p_a_r_a_m_e_t_e_r
              is substituted.
       ${_p_a_r_a_m_e_t_e_r::==_w_o_r_d}
              AAssssiiggnn DDeeffaauulltt VVaalluueess.  If _p_a_r_a_m_e_t_e_r is unset or null,  the  ex-
              pansion  of _w_o_r_d is assigned to _p_a_r_a_m_e_t_e_r.  The value of _p_a_r_a_m_e_-
              _t_e_r is then substituted.  Positional parameters and special  pa-
              rameters may not be assigned to in this way.
       ${_p_a_r_a_m_e_t_e_r::??_w_o_r_d}
              DDiissppllaayy  EErrrroorr iiff NNuullll oorr UUnnsseett.  If _p_a_r_a_m_e_t_e_r is null or unset,
              the expansion of _w_o_r_d (or a message to that effect  if  _w_o_r_d  is
              not  present) is written to the standard error and the shell, if
              it is not interactive, exits.  Otherwise, the value of _p_a_r_a_m_e_t_e_r
              is substituted.
       ${_p_a_r_a_m_e_t_e_r::++_w_o_r_d}
              UUssee AAlltteerrnnaattee VVaalluuee.  If _p_a_r_a_m_e_t_e_r is null or unset, nothing  is
              substituted, otherwise the expansion of _w_o_r_d is substituted.
       ${_p_a_r_a_m_e_t_e_r::_o_f_f_s_e_t}
       ${_p_a_r_a_m_e_t_e_r::_o_f_f_s_e_t::_l_e_n_g_t_h}
              SSuubbssttrriinngg  EExxppaannssiioonn.  Expands to up to _l_e_n_g_t_h characters of the
              value of _p_a_r_a_m_e_t_e_r starting at the character specified  by  _o_f_f_-
              _s_e_t.   If _p_a_r_a_m_e_t_e_r is @@ or **, an indexed array subscripted by @@
              or **, or an associative array name, the results  differ  as  de-
              scribed  below.   If _l_e_n_g_t_h is omitted, expands to the substring
              of the value of _p_a_r_a_m_e_t_e_r starting at the character specified by
              _o_f_f_s_e_t and extending to the end of the value.  _l_e_n_g_t_h and _o_f_f_s_e_t
              are arithmetic expressions (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN below).

              If _o_f_f_s_e_t evaluates to a number less than  zero,  the  value  is
              used as an offset in characters from the end of the value of _p_a_-
              _r_a_m_e_t_e_r.   If _l_e_n_g_t_h evaluates to a number less than zero, it is
              interpreted as an offset in characters from the end of the value
              of _p_a_r_a_m_e_t_e_r rather than a number of characters, and the  expan-
              sion  is  the  characters  between _o_f_f_s_e_t and that result.  Note
              that a negative offset must be separated from the  colon  by  at
              least one space to avoid being confused with the ::-- expansion.

              If  _p_a_r_a_m_e_t_e_r is @@ or **, the result is _l_e_n_g_t_h positional parame-
              ters beginning at _o_f_f_s_e_t.  A negative _o_f_f_s_e_t is  taken  relative
              to  one  greater  than  the greatest positional parameter, so an
              offset of -1 evaluates to the last positional parameter (or 0 if
              there are no positional parameters).  It is an  expansion  error
              if _l_e_n_g_t_h evaluates to a number less than zero.

              If _p_a_r_a_m_e_t_e_r is an indexed array name subscripted by @ or *, the
              result is the _l_e_n_g_t_h members of the array beginning with ${_p_a_r_a_-
              _m_e_t_e_r[_o_f_f_s_e_t]}.   A  negative  _o_f_f_s_e_t  is  taken relative to one
              greater than the maximum index of the specified array.  It is an
              expansion error if _l_e_n_g_t_h evaluates to a number less than zero.

              Substring expansion applied to an associative array produces un-
              defined results.

              Substring indexing is zero-based unless the  positional  parame-
              ters  are  used,  in  which case the indexing starts at 1 by de-
              fault.  If _o_f_f_s_e_t is 0, and the positional parameters are  used,
              $$00 is prefixed to the list.

       ${!!_p_r_e_f_i_x**}
       ${!!_p_r_e_f_i_x@@}
              NNaammeess  mmaattcchhiinngg pprreeffiixx.  Expands to the names of variables whose
              names begin with _p_r_e_f_i_x, separated by the first character of the
              IIFFSS special variable.  When _@ is used and the expansion  appears
              within  double  quotes, each variable name expands to a separate
              word.

       ${!!_n_a_m_e[_@]}
       ${!!_n_a_m_e[_*]}
              LLiisstt ooff aarrrraayy kkeeyyss.  If _n_a_m_e is an array  variable,  expands  to
              the  list  of array indices (keys) assigned in _n_a_m_e.  If _n_a_m_e is
              not an array, expands to 0 if _n_a_m_e is set  and  null  otherwise.
              When  _@  is used and the expansion appears within double quotes,
              each key expands to a separate word.

       ${##_p_a_r_a_m_e_t_e_r}
              PPaarraammeetteerr lleennggtthh.  The length in characters of the value of  _p_a_-
              _r_a_m_e_t_e_r  is substituted.  If _p_a_r_a_m_e_t_e_r is ** or @@, the value sub-
              stituted is the number of positional parameters.   If  _p_a_r_a_m_e_t_e_r
              is an array name subscripted by ** or @@, the value substituted is
              the number of elements in the array.  If _p_a_r_a_m_e_t_e_r is an indexed
              array  name subscripted by a negative number, that number is in-
              terpreted as relative to one greater than the maximum  index  of
              _p_a_r_a_m_e_t_e_r,  so  negative  indices count back from the end of the
              array, and an index of -1 references the last element.

       ${_p_a_r_a_m_e_t_e_r##_w_o_r_d}
       ${_p_a_r_a_m_e_t_e_r####_w_o_r_d}
              RReemmoovvee mmaattcchhiinngg pprreeffiixx ppaatttteerrnn.  The _w_o_r_d is expanded to produce
              a pattern just as in pathname expansion, and matched against the
              expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt--
              tteerrnn MMaattcchhiinngg below.  If the pattern matches  the  beginning  of
              the  value of _p_a_r_a_m_e_t_e_r, then the result of the expansion is the
              expanded value of _p_a_r_a_m_e_t_e_r with the shortest  matching  pattern
              (the  "#"  case) or the longest matching pattern (the "##" case)
              deleted.  If _p_a_r_a_m_e_t_e_r is @@ or **, the pattern removal  operation
              is  applied to each positional parameter in turn, and the expan-
              sion is the resultant list.  If _p_a_r_a_m_e_t_e_r is an  array  variable
              subscripted  with  @@  or **, the pattern removal operation is ap-
              plied to each member of the array in turn, and the expansion  is
              the resultant list.

       ${_p_a_r_a_m_e_t_e_r%%_w_o_r_d}
       ${_p_a_r_a_m_e_t_e_r%%%%_w_o_r_d}
              RReemmoovvee mmaattcchhiinngg ssuuffffiixx ppaatttteerrnn.  The _w_o_r_d is expanded to produce
              a pattern just as in pathname expansion, and matched against the
              expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt--
              tteerrnn  MMaattcchhiinngg below.  If the pattern matches a trailing portion
              of the expanded value of _p_a_r_a_m_e_t_e_r, then the result of  the  ex-
              pansion  is  the  expanded  value of _p_a_r_a_m_e_t_e_r with the shortest
              matching pattern (the "%" case) or the longest matching  pattern
              (the  "%%"  case)  deleted.  If _p_a_r_a_m_e_t_e_r is @@ or **, the pattern
              removal operation is applied to  each  positional  parameter  in
              turn,  and the expansion is the resultant list.  If _p_a_r_a_m_e_t_e_r is
              an array variable subscripted with @@ or **, the  pattern  removal
              operation  is  applied  to each member of the array in turn, and
              the expansion is the resultant list.

       ${_p_a_r_a_m_e_t_e_r//_p_a_t_t_e_r_n//_s_t_r_i_n_g}
       ${_p_a_r_a_m_e_t_e_r////_p_a_t_t_e_r_n//_s_t_r_i_n_g}
       ${_p_a_r_a_m_e_t_e_r//##_p_a_t_t_e_r_n//_s_t_r_i_n_g}
       ${_p_a_r_a_m_e_t_e_r//%%_p_a_t_t_e_r_n//_s_t_r_i_n_g}
              PPaatttteerrnn ssuubbssttiittuuttiioonn.  The _p_a_t_t_e_r_n is expanded to produce a pat-
              tern just as in pathname expansion.  _P_a_r_a_m_e_t_e_r is  expanded  and
              the  longest match of _p_a_t_t_e_r_n against its value is replaced with
              _s_t_r_i_n_g.  _s_t_r_i_n_g undergoes tilde expansion, parameter  and  vari-
              able  expansion,  arithmetic expansion, command and process sub-
              stitution, and quote removal.  The match is performed using  the
              rules described under PPaatttteerrnn MMaattcchhiinngg below.  In the first form
              above,  only  the  first  match  is  replaced.  If there are two
              slashes  separating  _p_a_r_a_m_e_t_e_r  and  _p_a_t_t_e_r_n  (the  second  form
              above),  all  matches  of  _p_a_t_t_e_r_n are replaced with _s_t_r_i_n_g.  If
              _p_a_t_t_e_r_n is preceded by ## (the third form above), it  must  match
              at the beginning of the expanded value of _p_a_r_a_m_e_t_e_r.  If _p_a_t_t_e_r_n
              is  preceded  by %% (the fourth form above), it must match at the
              end of the expanded value of _p_a_r_a_m_e_t_e_r.   If  the  expansion  of
              _s_t_r_i_n_g  is  null,  matches of _p_a_t_t_e_r_n are deleted.  If _s_t_r_i_n_g is
              null, matches of _p_a_t_t_e_r_n are deleted and the // following _p_a_t_t_e_r_n
              may be omitted.

              If the ppaattssuubb__rreeppllaacceemmeenntt shell option is enabled  using  sshhoopptt,
              any  unquoted  instances  of  &&  in _s_t_r_i_n_g are replaced with the
              matching portion of _p_a_t_t_e_r_n.

              Quoting any part of _s_t_r_i_n_g inhibits replacement in the expansion
              of the quoted portion, including replacement strings  stored  in
              shell  variables.   Backslash will escape && in _s_t_r_i_n_g; the back-
              slash is removed in order to permit a literal && in the  replace-
              ment  string.  Backslash can also be used to escape a backslash;
              \\\\ results in a literal backslash  in  the  replacement.   Users
              should  take  care  if _s_t_r_i_n_g is double-quoted to avoid unwanted
              interactions between the  backslash  and  double-quoting,  since
              backslash  has  special  meaning  within double quotes.  Pattern
              substitution performs the check for unquoted &&  after  expanding
              _s_t_r_i_n_g; shell programmers should quote any occurrences of && they
              want to be taken literally in the replacement and ensure any in-
              stances of && they want to be replaced are unquoted.

              If  the  nnooccaasseemmaattcchh  shell option is enabled, the match is per-
              formed without regard to the case of alphabetic characters.   If
              _p_a_r_a_m_e_t_e_r  is  @@  or **, the substitution operation is applied to
              each positional parameter in turn, and the expansion is the  re-
              sultant  list.   If  _p_a_r_a_m_e_t_e_r  is an array variable subscripted
              with @@ or **, the substitution operation is applied to each  mem-
              ber  of  the  array  in turn, and the expansion is the resultant
              list.

       ${_p_a_r_a_m_e_t_e_r^^_p_a_t_t_e_r_n}
       ${_p_a_r_a_m_e_t_e_r^^^^_p_a_t_t_e_r_n}
       ${_p_a_r_a_m_e_t_e_r,,_p_a_t_t_e_r_n}
       ${_p_a_r_a_m_e_t_e_r,,,,_p_a_t_t_e_r_n}
              CCaassee mmooddiiffiiccaattiioonn.  This expansion modifies the case  of  alpha-
              betic  characters in _p_a_r_a_m_e_t_e_r.  The _p_a_t_t_e_r_n is expanded to pro-
              duce a pattern just as in pathname expansion.  Each character in
              the expanded value of _p_a_r_a_m_e_t_e_r is tested against _p_a_t_t_e_r_n,  and,
              if  it  matches the pattern, its case is converted.  The pattern
              should not attempt to match more than one character.  The ^^  op-
              erator converts lowercase letters matching _p_a_t_t_e_r_n to uppercase;
              the ,, operator converts matching uppercase letters to lowercase.
              The  ^^^^  and ,,,, expansions convert each matched character in the
              expanded value; the ^^ and ,, expansions match  and  convert  only
              the  first character in the expanded value.  If _p_a_t_t_e_r_n is omit-
              ted, it is treated like a ??, which matches every character.   If
              _p_a_r_a_m_e_t_e_r  is @@ or **, the case modification operation is applied
              to each positional parameter in turn, and the expansion  is  the
              resultant  list.   If _p_a_r_a_m_e_t_e_r is an array variable subscripted
              with @@ or **, the case modification operation is applied to  each
              member  of the array in turn, and the expansion is the resultant
              list.

       ${_p_a_r_a_m_e_t_e_r@@_o_p_e_r_a_t_o_r}
              PPaarraammeetteerr ttrraannssffoorrmmaattiioonn.  The expansion is either a transforma-
              tion of the value of _p_a_r_a_m_e_t_e_r or  information  about  _p_a_r_a_m_e_t_e_r
              itself,  depending on the value of _o_p_e_r_a_t_o_r.  Each _o_p_e_r_a_t_o_r is a
              single letter:

              UU      The expansion is a string that is the value of  _p_a_r_a_m_e_t_e_r
                     with  lowercase alphabetic characters converted to upper-
                     case.
              uu      The expansion is a string that is the value of  _p_a_r_a_m_e_t_e_r
                     with the first character converted to uppercase, if it is
                     alphabetic.
              LL      The  expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
                     with uppercase alphabetic characters converted to  lower-
                     case.
              QQ      The  expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
                     quoted in a format that can be reused as input.
              EE      The expansion is a string that is the value of  _p_a_r_a_m_e_t_e_r
                     with  backslash  escape  sequences  expanded  as with the
                     $$''...'' quoting mechanism.
              PP      The expansion is a string that is the result of expanding
                     the value of _p_a_r_a_m_e_t_e_r as if it were a prompt string (see
                     PPRROOMMPPTTIINNGG below).
              AA      The expansion is a string in the form  of  an  assignment
                     statement  or  ddeeccllaarree  command  that, if evaluated, will
                     recreate _p_a_r_a_m_e_t_e_r with its attributes and value.
              KK      Produces a possibly-quoted version of the value of  _p_a_r_a_-
                     _m_e_t_e_r,  except  that  it prints the values of indexed and
                     associative arrays as  a  sequence  of  quoted  key-value
                     pairs (see AArrrraayyss above).  The keys and values are quoted
                     in a format that can be reused as input.
              aa      The  expansion is a string consisting of flag values rep-
                     resenting _p_a_r_a_m_e_t_e_r's attributes.
              kk      Like the K transformation, but expands the keys and  val-
                     ues  of  indexed and associative arrays to separate words
                     after word splitting.

              If _p_a_r_a_m_e_t_e_r is @@ or **, the operation is applied to  each  posi-
              tional  parameter  in  turn,  and the expansion is the resultant
              list.  If _p_a_r_a_m_e_t_e_r is an array variable subscripted with  @@  or
              **, the operation is applied to each member of the array in turn,
              and the expansion is the resultant list.

              The  result  of  the  expansion is subject to word splitting and
              pathname expansion as described below.

   CCoommmmaanndd SSuubbssttiittuuttiioonn
       _C_o_m_m_a_n_d _s_u_b_s_t_i_t_u_t_i_o_n allows the output of a command to replace the com-
       mand itself.  There are two standard forms:

              $$((_c_o_m_m_a_n_d))
       or (deprecated)
              ``_c_o_m_m_a_n_d``.

       BBaasshh performs the expansion by executing _c_o_m_m_a_n_d in a subshell environ-
       ment and replacing the command substitution with the standard output of
       the command, with any trailing newlines deleted.  Embedded newlines are
       not deleted, but they may be removed during word splitting.   The  com-
       mand  substitution  $$((ccaatt  _f_i_l_e))  can be replaced by the equivalent but
       faster $$((<< _f_i_l_e)).

       With the old-style backquote form of  substitution,  backslash  retains
       its  literal  meaning  except  when  followed by $$, ``, or \\.  The first
       backquote not preceded by a backslash terminates the command  substitu-
       tion.   When  using  the  $(_c_o_m_m_a_n_d)  form,  all characters between the
       parentheses make up the command; none are treated specially.

       There is an alternate form of command substitution:

              $${{_c _c_o_m_m_a_n_d;;}}

       which executes _c_o_m_m_a_n_d in the current execution  environment  and  cap-
       tures its output, again with trailing newlines removed.

       The character _c following the open brace must be a space, tab, newline,
       or  ||,  and the close brace must be in a position where a reserved word
       may appear (i.e., preceded by a command terminator such as  semicolon).
       BBaasshh allows the close brace to be joined to the remaining characters in
       the  word without being followed by a shell metacharacter as a reserved
       word would usually require.

       Any side effects of _c_o_m_m_a_n_d take effect immediately in the current exe-
       cution environment and persist in the  current  environment  after  the
       command completes (e.g., the eexxiitt builtin will exit the shell).

       This  type of command substitution superficially resembles executing an
       unnamed shell function: local variables are created  as  when  a  shell
       function  is  executing,  and the rreettuurrnn builtin forces _c_o_m_m_a_n_d to com-
       plete; however, the rest of the execution  environment,  including  the
       positional parameters, is shared with the caller.

       If  the  first character following the open brace is a ||, the construct
       expands to the value of the RREEPPLLYY shell  variable  after  _c_o_m_m_a_n_d  exe-
       cutes,  without removing any trailing newlines, and the standard output
       of _c_o_m_m_a_n_d remains the same as in the calling shell.  BBaasshh creates  RREE--
       PPLLYY as an initially-unset local variable when _c_o_m_m_a_n_d executes, and re-
       stores  RREEPPLLYY to the value it had before the command substitution after
       _c_o_m_m_a_n_d completes, as with any local variable.

       Command substitutions may be nested.  To nest when using the backquoted
       form, escape the inner backquotes with backslashes.

       If the substitution appears within double quotes, bbaasshh does not perform
       word splitting and pathname expansion on the results.

   AArriitthhmmeettiicc EExxppaannssiioonn
       Arithmetic expansion allows the evaluation of an arithmetic  expression
       and  the  substitution of the result.  The format for arithmetic expan-
       sion is:

              $$((((_e_x_p_r_e_s_s_i_o_n))))

       The _e_x_p_r_e_s_s_i_o_n undergoes the same expansions as if it were within  dou-
       ble  quotes,  but double quote characters in _e_x_p_r_e_s_s_i_o_n are not treated
       specially and are removed.  All tokens in the expression undergo  para-
       meter  and variable expansion, command substitution, and quote removal.
       The result is treated as the arithmetic  expression  to  be  evaluated.
       Arithmetic expansions may be nested.

       The  evaluation  is performed according to the rules listed below under
       AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN.  If _e_x_p_r_e_s_s_i_o_n is invalid, bbaasshh prints a message
       indicating failure and no substitution occurs.

   PPrroocceessss SSuubbssttiittuuttiioonn
       _P_r_o_c_e_s_s _s_u_b_s_t_i_t_u_t_i_o_n allows a process's input or output to be  referred
       to  using  a  filename.   It takes the form of <<((_l_i_s_t)) or >>((_l_i_s_t)).  The
       process _l_i_s_t is run asynchronously, and its input or output appears  as
       a filename.  This filename is passed as an argument to the current com-
       mand  as  the  result  of  the expansion.  If the >>((_l_i_s_t)) form is used,
       writing to the file will provide input for _l_i_s_t.  If the  <<((_l_i_s_t))  form
       is  used,  the  file passed as an argument should be read to obtain the
       output of _l_i_s_t.  Process substitution is supported on systems that sup-
       port named pipes (_F_I_F_O_s) or the //ddeevv//ffdd method of naming open files.

       When available, process substitution is performed  simultaneously  with
       parameter  and variable expansion, command substitution, and arithmetic
       expansion.

   WWoorrdd SSpplliittttiinngg
       The shell scans the results of parameter expansion,  command  substitu-
       tion,  and arithmetic expansion that did not occur within double quotes
       for _w_o_r_d _s_p_l_i_t_t_i_n_g.

       The shell treats each character of IIFFSS as a delimiter, and  splits  the
       results  of  the  other expansions into words using these characters as
       field terminators.

       If IIFFSS is unset, or its value is exactly <<ssppaaccee>><<ttaabb>><<nneewwlliinnee>>, the de-
       fault, then sequences of ssppaaccee, ttaabb, and nneewwlliinnee at the  beginning  and
       end  of the results of the previous expansions are ignored, and any se-
       quence of IIFFSS characters not at the beginning or end serves to  delimit
       words.   If  IIFFSS  has a value other than the default, then sequences of
       the whitespace characters ssppaaccee, ttaabb, and nneewwlliinnee are  ignored  at  the
       beginning  and  end of the word, as long as the whitespace character is
       in the value of IIFFSS (an IIFFSS whitespace character).   Any  character  in
       IIFFSS  that is not IIFFSS whitespace, along with any adjacent IIFFSS whitespace
       characters, delimits a field.  A sequence of IIFFSS whitespace  characters
       is also treated as a delimiter.

       If  the  value of IIFFSS is null, no word splitting occurs.  If IIFFSS is un-
       set, word splitting behaves as if it contained  the  default  value  of
       <<ssppaaccee>><<ttaabb>><<nneewwlliinnee>>.

       Explicit  null arguments ("""" or '''') are retained and passed to commands
       as empty strings.  Unquoted implicit null arguments, resulting from the
       expansion of parameters that have no values, are removed.  If a parame-
       ter with no value is expanded within double quotes, a null argument re-
       sults and is retained and passed to a command as an empty string.  When
       a quoted null argument appears as part of a  word  whose  expansion  is
       non-null,  the  null argument is removed.  That is, the word "-d''" be-
       comes "-d" after word splitting and null argument removal.

       Note that if no expansion occurs, no splitting is performed.

   PPaatthhnnaammee EExxppaannssiioonn
       After word splitting, unless the --ff option has  been  set,  bbaasshh  scans
       each  word  for the characters **, ??, and [[.  If one of these characters
       appears, and is not quoted, then the word is regarded as a _p_a_t_t_e_r_n, and
       replaced with an alphabetically sorted list of filenames  matching  the
       pattern  (see  PPaatttteerrnn  MMaattcchhiinngg  below).  If no matching filenames are
       found, and the shell option nnuullllgglloobb is not enabled, the word  is  left
       unchanged.   If  the  nnuullllgglloobb option is set, and no matches are found,
       the word is removed.  If the ffaaiillgglloobb  shell  option  is  set,  and  no
       matches  are  found, an error message is printed and the command is not
       executed.  If the shell option nnooccaasseegglloobb is enabled, the match is per-
       formed without regard to the case of  alphabetic  characters.   When  a
       pattern  is used for pathname expansion, the character "." at the start
       of a name or immediately following a slash must be matched  explicitly,
       unless  the  shell  option ddoottgglloobb is set.  In order to match the file-
       names "." and "..", the pattern  must  begin  with  "."  (for  example,
       ".?"), even if ddoottgglloobb is set.  If the gglloobbsskkiippddoottss shell option is en-
       abled,  the filenames "." and ".." never match, even if the pattern be-
       gins with a "." When not matching pathnames, the "." character  is  not
       treated  specially.  When matching a pathname, the slash character must
       always be matched explicitly by a slash in the pattern,  but  in  other
       matching  contexts  it can be matched by a special pattern character as
       described below under PPaatttteerrnn MMaattcchhiinngg.  See the description  of  sshhoopptt
       below under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS for a description of the nnooccaasseegglloobb,
       nnuullllgglloobb, gglloobbsskkiippddoottss, ffaaiillgglloobb, and ddoottgglloobb shell options.

       The  GGLLOOBBIIGGNNOORREE  shell variable may be used to restrict the set of file
       names matching a _p_a_t_t_e_r_n.  If GGLLOOBBIIGGNNOORREE is  set,  each  matching  file
       name  that  also  matches  one of the patterns in GGLLOOBBIIGGNNOORREE is removed
       from the list of matches.  If the nnooccaasseegglloobb option is set, the  match-
       ing  against  the patterns in GGLLOOBBIIGGNNOORREE is performed without regard to
       case.  The filenames "." and ".." are always ignored when GGLLOOBBIIGGNNOORREE is
       set and not null.  However, setting GGLLOOBBIIGGNNOORREE to a non-null value  has
       the effect of enabling the ddoottgglloobb shell option, so all other filenames
       beginning  with  a Q . will match.  To get the old behavior of ignoring
       filenames beginning with a ".", make ".*"  one of the patterns in  GGLLOO--
       BBIIGGNNOORREE.  The ddoottgglloobb option is disabled when GGLLOOBBIIGGNNOORREE is unset.  The
       pattern matching honors the setting of the eexxttgglloobb shell option.

       The  GGLLOOBBSSOORRTT  variable  controls how the results of pathname expansion
       are sorted, as described above.

       PPaatttteerrnn MMaattcchhiinngg

       Any character that appears in a pattern, other than the special pattern
       characters described below, matches itself.  The NUL character may  not
       occur  in  a pattern.  A backslash escapes the following character; the
       escaping backslash is discarded when  matching.   The  special  pattern
       characters must be quoted if they are to be matched literally.

       The special pattern characters have the following meanings:

              **      Matches  any string, including the null string.  When the
                     gglloobbssttaarr shell option is enabled, and  **  is  used  in  a
                     pathname  expansion  context,  two  adjacent **s used as a
                     single pattern will match all files and zero or more  di-
                     rectories  and  subdirectories.   If followed by a //, two
                     adjacent **s will match only directories  and  subdirecto-
                     ries.
              ??      Matches any single character.
              [[...]]  Matches  any  one  of the enclosed characters.  A pair of
                     characters separated by a hyphen denotes a _r_a_n_g_e  _e_x_p_r_e_s_-
                     _s_i_o_n;  any character that falls between those two charac-
                     ters, inclusive, using the current locale's collating se-
                     quence and character set, is matched.  If the first char-
                     acter following the [[ is a !!  or a ^^ then  any  character
                     not enclosed is matched.  The sorting order of characters
                     in  range expressions, and the characters included in the
                     range, are determined by the current locale and the  val-
                     ues  of the LLCC__CCOOLLLLAATTEE or LLCC__AALLLL shell variables, if set.
                     To obtain the traditional interpretation of range expres-
                     sions, where [[aa--dd]] is equivalent to [[aabbccdd]], set value  of
                     the  LLCC__AALLLL  shell variable to CC, or enable the gglloobbaassccii--
                     iirraannggeess shell option.  A -- may be matched by including it
                     as the first or last character in the set.  A  ]]  may  be
                     matched  by  including  it  as the first character in the
                     set.

                     Within [[ and ]], _c_h_a_r_a_c_t_e_r _c_l_a_s_s_e_s can be specified  using
                     the syntax [[::_c_l_a_s_s::]], where _c_l_a_s_s is one of the following
                     classes defined in the POSIX standard:

                     aallnnuumm  aallpphhaa  aasscciiii  bbllaannkk  ccnnttrrll ddiiggiitt ggrraapphh lloowweerr pprriinntt
                     ppuunncctt ssppaaccee uuppppeerr wwoorrdd xxddiiggiitt

                     A character class matches any character belonging to that
                     class.  The wwoorrdd character class matches letters, digits,
                     and the character _.

                     Within [[ and ]], an _e_q_u_i_v_a_l_e_n_c_e _c_l_a_s_s can be specified us-
                     ing the syntax [[==_c==]], which matches all  characters  with
                     the  same collation weight (as defined by the current lo-
                     cale) as the character _c.

                     Within [[ and ]], the syntax [[.._s_y_m_b_o_l..]] matches the collat-
                     ing symbol _s_y_m_b_o_l.

       If the eexxttgglloobb shell option is enabled using  the  sshhoopptt  builtin,  the
       shell  recognizes  several extended pattern matching operators.  In the
       following description, a _p_a_t_t_e_r_n_-_l_i_s_t is a list of one or more patterns
       separated by a ||.  Composite patterns may be formed using one  or  more
       of the following sub-patterns:

              ??((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches zero or one occurrence of the given patterns
              **((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches zero or more occurrences of the given patterns
              ++((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches one or more occurrences of the given patterns
              @@((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches one of the given patterns
              !!((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches anything except one of the given patterns

       The eexxttgglloobb option changes the behavior of the parser, since the paren-
       theses  are  normally  treated as operators with syntactic meaning.  To
       ensure that extended matching patterns are parsed correctly, make  sure
       that  eexxttgglloobb  is enabled before parsing constructs containing the pat-
       terns, including shell functions and command substitutions.

       When matching filenames, the ddoottgglloobb shell option determines the set of
       filenames that are tested: when ddoottgglloobb is enabled, the  set  of  file-
       names  includes  all files beginning with ".", but "." and ".." must be
       matched by a pattern or sub-pattern that begins with a dot; when it  is
       disabled, the set does not include any filenames beginning with "." un-
       less  the pattern or sub-pattern begins with a ".".  As above, "." only
       has a special meaning when matching filenames.

       Complicated extended pattern matching against long strings is slow, es-
       pecially when the patterns contain alternations and the strings contain
       multiple matches.  Using separate matches against shorter  strings,  or
       using arrays of strings instead of a single long string, may be faster.

   QQuuoottee RReemmoovvaall
       After the preceding expansions, all unquoted occurrences of the charac-
       ters  \\,  '', and "" that did not result from one of the above expansions
       are removed.

RREEDDIIRREECCTTIIOONN
       Before a command is executed, its input and output  may  be  _r_e_d_i_r_e_c_t_e_d
       using  a special notation interpreted by the shell.  _R_e_d_i_r_e_c_t_i_o_n allows
       commands' file handles to be duplicated, opened, closed, made to  refer
       to different files, and can change the files the command reads from and
       writes  to.  Redirection may also be used to modify file handles in the
       current shell execution environment.  The following redirection  opera-
       tors may precede or appear anywhere within a _s_i_m_p_l_e _c_o_m_m_a_n_d or may fol-
       low  a  _c_o_m_m_a_n_d.   Redirections are processed in the order they appear,
       from left to right.

       Each redirection that may be preceded by a file descriptor  number  may
       instead be preceded by a word of the form {_v_a_r_n_a_m_e}.  In this case, for
       each redirection operator except >&- and <&-, the shell will allocate a
       file  descriptor  greater than or equal to 10 and assign it to _v_a_r_n_a_m_e.
       If >&- or <&- is preceded by {_v_a_r_n_a_m_e}, the value  of  _v_a_r_n_a_m_e  defines
       the  file  descriptor to close.  If {_v_a_r_n_a_m_e} is supplied, the redirec-
       tion persists beyond the scope of the command, allowing the shell  pro-
       grammer  to  manage  the  file  descriptor's  lifetime  manually.   The
       vvaarrrreeddiirr__cclloossee shell option manages this behavior.

       In the following descriptions, if the file descriptor number  is  omit-
       ted,  and  the  first  character  of the redirection operator is <<, the
       redirection refers to the standard input (file descriptor 0).   If  the
       first  character  of  the  redirection  operator  is >>, the redirection
       refers to the standard output (file descriptor 1).

       The word following the redirection operator in the  following  descrip-
       tions,  unless  otherwise noted, is subjected to brace expansion, tilde
       expansion, parameter  and  variable  expansion,  command  substitution,
       arithmetic  expansion,  quote  removal,  pathname  expansion,  and word
       splitting.  If it expands to more than one word, bbaasshh reports an error.

       Note that the order of redirections is significant.  For  example,  the
       command

              ls >> dirlist 2>>&&1

       directs  both  standard  output and standard error to the file _d_i_r_l_i_s_t,
       while the command

              ls 2>>&&1 >> dirlist

       directs only the standard output to file _d_i_r_l_i_s_t, because the  standard
       error  was duplicated from the standard output before the standard out-
       put was redirected to _d_i_r_l_i_s_t.

       BBaasshh handles several filenames specially when they are used in redirec-
       tions, as described in the following table.  If the operating system on
       which bbaasshh is running provides these special files, bash will use them;
       otherwise it will emulate them internally with the  behavior  described
       below.

              //ddeevv//ffdd//_f_d
                     If  _f_d  is  a valid integer, file descriptor _f_d is dupli-
                     cated.
              //ddeevv//ssttddiinn
                     File descriptor 0 is duplicated.
              //ddeevv//ssttddoouutt
                     File descriptor 1 is duplicated.
              //ddeevv//ssttddeerrrr
                     File descriptor 2 is duplicated.
              //ddeevv//ttccpp//_h_o_s_t//_p_o_r_t
                     If _h_o_s_t is a valid hostname or Internet address, and _p_o_r_t
                     is an integer port number or service name, bbaasshh  attempts
                     to open the corresponding TCP socket.
              //ddeevv//uuddpp//_h_o_s_t//_p_o_r_t
                     If _h_o_s_t is a valid hostname or Internet address, and _p_o_r_t
                     is  an integer port number or service name, bbaasshh attempts
                     to open the corresponding UDP socket.

       A failure to open or create a file causes the redirection to fail.

       Redirections using file descriptors greater than 9 should be used  with
       care,  as they may conflict with file descriptors the shell uses inter-
       nally.

   RReeddiirreeccttiinngg IInnppuutt
       Redirection of input causes the file whose name results from the expan-
       sion of _w_o_r_d to be opened for reading on  file  descriptor  _n,  or  the
       standard input (file descriptor 0) if _n is not specified.

       The general format for redirecting input is:

              [_n]<<_w_o_r_d

   RReeddiirreeccttiinngg OOuuttppuutt
       Redirection  of  output causes the file whose name results from the ex-
       pansion of _w_o_r_d to be opened for writing on file descriptor _n,  or  the
       standard output (file descriptor 1) if _n is not specified.  If the file
       does  not exist it is created; if it does exist it is truncated to zero
       size.

       The general format for redirecting output is:

              [_n]>>_w_o_r_d

       If the redirection operator is >>, and the nnoocclloobbbbeerr option to  the  sseett
       builtin  has  been enabled, the redirection will fail if the file whose
       name results from the expansion of _w_o_r_d exists and is a  regular  file.
       If the redirection operator is >>||, or the redirection operator is >> and
       the  nnoocclloobbbbeerr  option  to  the sseett builtin command is not enabled, the
       redirection is attempted even if the file named by _w_o_r_d exists.

   AAppppeennddiinngg RReeddiirreecctteedd OOuuttppuutt
       Redirection of output in this fashion causes the file  whose  name  re-
       sults from the expansion of _w_o_r_d to be opened for appending on file de-
       scriptor  _n,  or  the  standard  output (file descriptor 1) if _n is not
       specified.  If the file does not exist it is created.

       The general format for appending output is:

              [_n]>>>>_w_o_r_d

   RReeddiirreeccttiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr
       This construct allows both the standard output (file descriptor 1)  and
       the  standard  error output (file descriptor 2) to be redirected to the
       file whose name is the expansion of _w_o_r_d.

       There are two formats for redirecting standard output and standard  er-
       ror:

              &&>>_w_o_r_d
       and
              >>&&_w_o_r_d

       Of the two forms, the first is preferred.  This is semantically equiva-
       lent to

              >>_w_o_r_d 2>>&&1

       When  using  the second form, _w_o_r_d may not expand to a number or --.  If
       it does, other redirection operators apply (see  DDuupplliiccaattiinngg  FFiillee  DDee--
       ssccrriippttoorrss below) for compatibility reasons.

   AAppppeennddiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr
       This  construct allows both the standard output (file descriptor 1) and
       the standard error output (file descriptor 2) to  be  appended  to  the
       file whose name is the expansion of _w_o_r_d.

       The format for appending standard output and standard error is:

              &&>>>>_w_o_r_d

       This is semantically equivalent to

              >>>>_w_o_r_d 2>>&&1

       (see DDuupplliiccaattiinngg FFiillee DDeessccrriippttoorrss below).

   HHeerree DDooccuummeennttss
       This  type  of  redirection  instructs the shell to read input from the
       current source until it reads a line containing only _d_e_l_i_m_i_t_e_r (with no
       trailing blanks).  All of the lines read up to that point are then used
       as the standard input (or file descriptor _n if _n is  specified)  for  a
       command.

       The format of here-documents is:

              [_n]<<<<[--]_w_o_r_d
                      _h_e_r_e_-_d_o_c_u_m_e_n_t
              _d_e_l_i_m_i_t_e_r

       No  parameter  and variable expansion, command substitution, arithmetic
       expansion, or pathname expansion is performed on _w_o_r_d.

       If any part of _w_o_r_d is quoted, the _d_e_l_i_m_i_t_e_r is the result of quote re-
       moval on _w_o_r_d, and the lines in the here-document are not expanded.  If
       _w_o_r_d is unquoted, the _d_e_l_i_m_i_t_e_r is _w_o_r_d itself, all lines of the  here-
       document  are  subjected  to parameter expansion, command substitution,
       and arithmetic expansion, the character sequence \\<<nneewwlliinnee>> is ignored,
       and \\ must be used to quote the characters \\, $$, and ``.

       If the redirection operator is <<<<--, then all leading tab characters are
       stripped from input lines and the line containing _d_e_l_i_m_i_t_e_r.  This  al-
       lows  here-documents  within  shell scripts to be indented in a natural
       fashion.

   HHeerree SSttrriinnggss
       A variant of here documents, the format is:

              [_n]<<<<<<_w_o_r_d

       The _w_o_r_d undergoes tilde expansion, parameter and  variable  expansion,
       command  substitution,  arithmetic expansion, and quote removal.  Path-
       name expansion and word splitting are not  performed.   The  result  is
       supplied as a single string, with a newline appended, to the command on
       its standard input (or file descriptor _n if _n is specified).

   DDuupplliiccaattiinngg FFiillee DDeessccrriippttoorrss
       The redirection operator

              [_n]<<&&_w_o_r_d

       is used to duplicate input file descriptors.  If _w_o_r_d expands to one or
       more  digits,  the file descriptor denoted by _n is made to be a copy of
       that file descriptor.  If the digits in _w_o_r_d do not specify a file  de-
       scriptor open for input, a redirection error occurs.  If _w_o_r_d evaluates
       to --, file descriptor _n is closed.  If _n is not specified, the standard
       input (file descriptor 0) is used.

       The operator

              [_n]>>&&_w_o_r_d

       is  used  similarly  to duplicate output file descriptors.  If _n is not
       specified, the standard output (file descriptor 1)  is  used.   If  the
       digits  in  _w_o_r_d  do  not  specify a file descriptor open for output, a
       redirection error occurs.  If _w_o_r_d evaluates to --, file descriptor _n is
       closed.  As a special case, if _n is omitted, and _w_o_r_d does  not  expand
       to  one or more digits or --, the standard output and standard error are
       redirected as described previously.

   MMoovviinngg FFiillee DDeessccrriippttoorrss
       The redirection operator

              [_n]<<&&_d_i_g_i_t--

       moves the file descriptor _d_i_g_i_t to file descriptor _n, or  the  standard
       input (file descriptor 0) if _n is not specified.  _d_i_g_i_t is closed after
       being duplicated to _n.

       Similarly, the redirection operator

              [_n]>>&&_d_i_g_i_t--

       moves  the  file descriptor _d_i_g_i_t to file descriptor _n, or the standard
       output (file descriptor 1) if _n is not specified.

   OOppeenniinngg FFiillee DDeessccrriippttoorrss ffoorr RReeaaddiinngg aanndd WWrriittiinngg
       The redirection operator

              [_n]<<>>_w_o_r_d

       causes the file whose name is the expansion of _w_o_r_d to  be  opened  for
       both  reading and writing on file descriptor _n, or on file descriptor 0
       if _n is not specified.  If the file does not exist, it is created.

AALLIIAASSEESS
       _A_l_i_a_s_e_s allow a string to be substituted for a word that is in a  posi-
       tion  in  the input where it can be the first word of a simple command.
       Aliases have names and corresponding values that are set and unset  us-
       ing  the aalliiaass and uunnaalliiaass builtin commands (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS
       below).

       If the shell reads an unquoted word in the right  position,  it  checks
       the  word  to see if it matches an alias name. If it matches, the shell
       replaces the word with the alias value, and reads that value as  if  it
       had been read instead of the word.  The shell doesn't look at any char-
       acters following the word before attempting alias substitution.

       The  characters  //,  $$, ``, and == and any of the shell _m_e_t_a_c_h_a_r_a_c_t_e_r_s or
       quoting characters listed above may not appear in an alias  name.   The
       replacement  text  may  contain  any valid shell input, including shell
       metacharacters.  The first word of the replacement text is  tested  for
       aliases, but a word that is identical to an alias being expanded is not
       expanded a second time.  This means that one may alias llss to llss --FF, for
       instance,  and  bbaasshh does not try to recursively expand the replacement
       text.

       If the last character of the alias value is a _b_l_a_n_k, then the next com-
       mand word following the alias is also checked for alias expansion.

       Aliases are created and listed with the aalliiaass command, and removed with
       the uunnaalliiaass command.

       There is no mechanism for using arguments in the replacement text.   If
       arguments are needed, use a shell function (see FFUUNNCCTTIIOONNSS below).

       Aliases  are not expanded when the shell is not interactive, unless the
       eexxppaanndd__aalliiaasseess shell option is set using sshhoopptt (see the description  of
       sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

       The  rules  concerning  the  definition and use of aliases are somewhat
       confusing.  BBaasshh always reads at least one complete line of input,  and
       all  lines that make up a compound command, before executing any of the
       commands on that line or the compound command.   Aliases  are  expanded
       when  a  command is read, not when it is executed.  Therefore, an alias
       definition appearing on the same line as another command does not  take
       effect  until  the  next line of input is read.  The commands following
       the alias definition on that line are not affected by  the  new  alias.
       This  behavior  is  also an issue when functions are executed.  Aliases
       are expanded when a function definition is read, not when the  function
       is  executed,  because a function definition is itself a command.  As a
       consequence, aliases defined in a function are not available until  af-
       ter  that  function  is executed.  To be safe, always put alias defini-
       tions on a separate line, and do not use aalliiaass in compound commands.

       For almost every purpose, aliases are superseded by shell functions.

FFUUNNCCTTIIOONNSS
       A shell function, defined  as  described  above  under  SSHHEELLLL  GGRRAAMMMMAARR,
       stores  a  series  of commands for later execution.  When the name of a
       shell function is used as a simple command name, the list  of  commands
       associated with that function name is executed.  Functions are executed
       in  the  context of the current shell; no new process is created to in-
       terpret them (contrast this with the  execution  of  a  shell  script).
       When  a  function is executed, the arguments to the function become the
       positional parameters during its execution.  The special parameter ## is
       updated to reflect the change.  Special parameter 00 is unchanged.   The
       first  element of the FFUUNNCCNNAAMMEE variable is set to the name of the func-
       tion while the function is executing.

       All other aspects of the shell execution environment are identical  be-
       tween  a  function  and its caller with these exceptions: the DDEEBBUUGG and
       RREETTUURRNN traps (see the description  of  the  ttrraapp  builtin  under  SSHHEELLLL
       BBUUIILLTTIINN  CCOOMMMMAANNDDSS below) are not inherited unless the function has been
       given the ttrraaccee attribute (see the description of the  ddeeccllaarree  builtin
       below)  or  the --oo ffuunnccttrraaccee shell option has been enabled with the sseett
       builtin (in which case all  functions  inherit  the  DDEEBBUUGG  and  RREETTUURRNN
       traps),  and the EERRRR trap is not inherited unless the --oo eerrrrttrraaccee shell
       option has been enabled.

       Variables local to the function may be declared with the llooccaall  builtin
       command  (_l_o_c_a_l _v_a_r_i_a_b_l_e_s).  Ordinarily, variables and their values are
       shared between the function and its caller.  If a variable is  declared
       llooccaall,  the variable's visible scope is restricted to that function and
       its children (including the functions it calls).

       In the following description, the _c_u_r_r_e_n_t _s_c_o_p_e is a currently- execut-
       ing function.  Previous scopes consist of that function's caller and so
       on, back to the "global" scope, where the shell is  not  executing  any
       shell function.  Consequently, a local variable at the current scope is
       a variable declared using the llooccaall or ddeeccllaarree builtins in the function
       that is currently executing.

       Local  variables "shadow" variables with the same name declared at pre-
       vious scopes.  For instance, a local variable declared  in  a  function
       hides  a  global  variable of the same name: references and assignments
       refer to the local variable, leaving the  global  variable  unmodified.
       When the function returns, the global variable is once again visible.

       The  shell  uses  _d_y_n_a_m_i_c  _s_c_o_p_i_n_g  to  control a variable's visibility
       within functions.  With dynamic scoping, visible  variables  and  their
       values  are a result of the sequence of function calls that caused exe-
       cution to reach the current function.  The value of a variable  that  a
       function  sees  depends on its value within its caller, if any, whether
       that caller is the global scope or another  shell  function.   This  is
       also the value that a local variable declaration shadows, and the value
       that is restored when the function returns.

       For  example, if a variable _v_a_r is declared as local in function _f_u_n_c_1,
       and _f_u_n_c_1 calls another function _f_u_n_c_2, references  to  _v_a_r  made  from
       within _f_u_n_c_2 will resolve to the local variable _v_a_r from _f_u_n_c_1, shadow-
       ing any global variable named _v_a_r.

       The uunnsseett builtin also acts using the same dynamic scope: if a variable
       is local to the current scope, uunnsseett will unset it; otherwise the unset
       will  refer  to  the  variable  found in any calling scope as described
       above.  If a variable at the current local scope is unset, it will  re-
       main  so  (appearing as unset) until it is reset in that scope or until
       the function returns.  Once the function returns, any instance  of  the
       variable at a previous scope will become visible.  If the unset acts on
       a  variable  at  a previous scope, any instance of a variable with that
       name that had been shadowed will become visible (see below how the  lloo--
       ccaallvvaarr__uunnsseett shell option changes this behavior).

       The  FFUUNNCCNNEESSTT  variable,  if set to a numeric value greater than 0, de-
       fines a maximum function nesting level.  Function invocations that  ex-
       ceed the limit cause the entire command to abort.

       If  the  builtin command rreettuurrnn is executed in a function, the function
       completes and execution resumes with the next command after  the  func-
       tion call.  Any command associated with the RREETTUURRNN trap is executed be-
       fore  execution  resumes.  When a function completes, the values of the
       positional parameters and the special parameter ## are restored  to  the
       values they had prior to the function's execution.

       Function  names and definitions may be listed with the --ff option to the
       ddeeccllaarree or ttyyppeesseett builtin commands.  The --FF option to ddeeccllaarree or ttyyppee--
       sseett will list the function names only (and optionally the  source  file
       and  line  number, if the eexxttddeebbuugg shell option is enabled).  Functions
       may be exported so that child shell processes (those created when  exe-
       cuting  a  separate  shell  invocation) automatically have them defined
       with the --ff option to the eexxppoorrtt builtin.  A function definition may be
       deleted using the --ff option to the uunnsseett builtin.

       Functions may be recursive.  The FFUUNNCCNNEESSTT variable may be used to limit
       the depth of the function call stack and restrict the number  of  func-
       tion invocations.  By default, no limit is imposed on the number of re-
       cursive calls.

AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN
       The  shell allows arithmetic expressions to be evaluated, under certain
       circumstances (see the lleett and ddeeccllaarree builtin commands,  the  ((((  com-
       pound command, and AArriitthhmmeettiicc EExxppaannssiioonn).  Evaluation is done in fixed-
       width  integers  with  no  check  for overflow, though division by 0 is
       trapped and flagged as an error.  The operators and  their  precedence,
       associativity,  and values are the same as in the C language.  The fol-
       lowing list of operators is grouped into levels of equal-precedence op-
       erators.  The levels are listed in order of decreasing precedence.

       _i_d++++ _i_d----
              variable post-increment and post-decrement
       -- ++    unary minus and plus
       ++++_i_d ----_i_d
              variable pre-increment and pre-decrement
       !! ~~    logical and bitwise negation
       ****     exponentiation
       ** // %%  multiplication, division, remainder
       ++ --    addition, subtraction
       <<<< >>>>  left and right bitwise shifts
       <<== >>== << >>
              comparison
       ==== !!==  equality and inequality
       &&      bitwise AND
       ^^      bitwise exclusive OR
       ||      bitwise OR
       &&&&     logical AND
       ||||     logical OR
       _e_x_p_r??_e_x_p_r::_e_x_p_r
              conditional operator
       == **== //== %%== ++== --== <<<<== >>>>== &&== ^^== ||==
              assignment
       _e_x_p_r_1 ,, _e_x_p_r_2
              comma

       Shell variables are allowed as operands; parameter  expansion  is  per-
       formed before the expression is evaluated.  Within an expression, shell
       variables  may  also  be referenced by name without using the parameter
       expansion syntax.  A shell variable that is null or unset evaluates  to
       0 when referenced by name without using the parameter expansion syntax.
       The  value  of a variable is evaluated as an arithmetic expression when
       it is referenced, or when a variable which has been given  the  _i_n_t_e_g_e_r
       attribute using ddeeccllaarree --ii is assigned a value.  A null value evaluates
       to  0.   A shell variable need not have its _i_n_t_e_g_e_r attribute turned on
       to be used in an expression.

       Integer constants follow the C language definition, without suffixes or
       character constants.  Constants with a leading 0 are interpreted as oc-
       tal numbers.  A leading 0x or 0X denotes hexadecimal.  Otherwise,  num-
       bers  take the form [_b_a_s_e_#]n, where the optional _b_a_s_e is a decimal num-
       ber between 2 and 64 representing the arithmetic base, and _n is a  num-
       ber  in  that  base.   If _b_a_s_e_# is omitted, then base 10 is used.  When
       specifying _n, if a non-digit is required, the digits greater than 9 are
       represented by the lowercase letters, the uppercase letters, @, and  _,
       in  that order.  If _b_a_s_e is less than or equal to 36, lowercase and up-
       percase letters may be used interchangeably to  represent  numbers  be-
       tween 10 and 35.

       Operators  are  evaluated  in  order of precedence.  Sub-expressions in
       parentheses are evaluated first and may override the  precedence  rules
       above.

CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS
       Conditional  expressions  are  used  by the [[[[ compound command and the
       tteesstt and [[ builtin commands to test file attributes and perform  string
       and  arithmetic  comparisons.   The tteesstt and [[ commands determine their
       behavior based on the number of  arguments;  see  the  descriptions  of
       those commands for any other command-specific actions.

       Expressions  are  formed  from the following unary or binary primaries.
       BBaasshh handles several filenames specially when they are used in  expres-
       sions.  If the operating system on which bbaasshh is running provides these
       special  files,  bash will use them; otherwise it will emulate them in-
       ternally with this behavior: If any _f_i_l_e argument to one  of  the  pri-
       maries is of the form _/_d_e_v_/_f_d_/_n, then file descriptor _n is checked.  If
       the  _f_i_l_e  argument  to  one  of  the  primaries  is one of _/_d_e_v_/_s_t_d_i_n,
       _/_d_e_v_/_s_t_d_o_u_t, or _/_d_e_v_/_s_t_d_e_r_r, file descriptor 0, 1, or 2,  respectively,
       is checked.

       Unless otherwise specified, primaries that operate on files follow sym-
       bolic links and operate on the target of the link, rather than the link
       itself.

       When  used with [[[[, or when the shell is in _p_o_s_i_x _m_o_d_e, the << and >> op-
       erators sort lexicographically using  the  current  locale.   When  the
       shell  is  not in _p_o_s_i_x _m_o_d_e, the tteesstt command sorts using ASCII order-
       ing.

       --aa _f_i_l_e
              True if _f_i_l_e exists.
       --bb _f_i_l_e
              True if _f_i_l_e exists and is a block special file.
       --cc _f_i_l_e
              True if _f_i_l_e exists and is a character special file.
       --dd _f_i_l_e
              True if _f_i_l_e exists and is a directory.
       --ee _f_i_l_e
              True if _f_i_l_e exists.
       --ff _f_i_l_e
              True if _f_i_l_e exists and is a regular file.
       --gg _f_i_l_e
              True if _f_i_l_e exists and is set-group-id.
       --hh _f_i_l_e
              True if _f_i_l_e exists and is a symbolic link.
       --kk _f_i_l_e
              True if _f_i_l_e exists and its "sticky" bit is set.
       --pp _f_i_l_e
              True if _f_i_l_e exists and is a named pipe (FIFO).
       --rr _f_i_l_e
              True if _f_i_l_e exists and is readable.
       --ss _f_i_l_e
              True if _f_i_l_e exists and has a size greater than zero.
       --tt _f_d  True if file descriptor _f_d is open and refers to a terminal.
       --uu _f_i_l_e
              True if _f_i_l_e exists and its set-user-id bit is set.
       --ww _f_i_l_e
              True if _f_i_l_e exists and is writable.
       --xx _f_i_l_e
              True if _f_i_l_e exists and is executable.
       --GG _f_i_l_e
              True if _f_i_l_e exists and is owned by the effective group id.
       --LL _f_i_l_e
              True if _f_i_l_e exists and is a symbolic link.
       --NN _f_i_l_e
              True if _f_i_l_e exists and has been  modified  since  it  was  last
              read.
       --OO _f_i_l_e
              True if _f_i_l_e exists and is owned by the effective user id.
       --SS _f_i_l_e
              True if _f_i_l_e exists and is a socket.
       _f_i_l_e_1 --eeff _f_i_l_e_2
              True  if _f_i_l_e_1 and _f_i_l_e_2 refer to the same device and inode num-
              bers.
       _f_i_l_e_1 -nntt _f_i_l_e_2
              True if _f_i_l_e_1 is newer (according  to  modification  date)  than
              _f_i_l_e_2, or if _f_i_l_e_1 exists and _f_i_l_e_2 does not.
       _f_i_l_e_1 -oott _f_i_l_e_2
              True  if _f_i_l_e_1 is older than _f_i_l_e_2, or if _f_i_l_e_2 exists and _f_i_l_e_1
              does not.
       --oo _o_p_t_n_a_m_e
              True if the shell option _o_p_t_n_a_m_e is enabled.  See  the  list  of
              options  under  the  description  of  the  --oo  option to the sseett
              builtin below.
       --vv _v_a_r_n_a_m_e
              True if the shell variable _v_a_r_n_a_m_e is set (has been  assigned  a
              value).   If  _v_a_r_n_a_m_e  is  an  indexed  array variable name sub-
              scripted by _@ or _*, this returns true if the array has  any  set
              elements.  If _v_a_r_n_a_m_e is an associative array variable name sub-
              scripted  by  _@  or _*, this returns true if an element with that
              key is set.
       --RR _v_a_r_n_a_m_e
              True if the shell variable _v_a_r_n_a_m_e is set and is a  name  refer-
              ence.
       --zz _s_t_r_i_n_g
              True if the length of _s_t_r_i_n_g is zero.
       _s_t_r_i_n_g
       --nn _s_t_r_i_n_g
              True if the length of _s_t_r_i_n_g is non-zero.

       _s_t_r_i_n_g_1 ==== _s_t_r_i_n_g_2
       _s_t_r_i_n_g_1 == _s_t_r_i_n_g_2
              True  if  the strings are equal.  == should be used with the tteesstt
              command for POSIX conformance.  When used with the  [[[[  command,
              this performs pattern matching as described above (CCoommppoouunndd CCoomm--
              mmaannddss).

       _s_t_r_i_n_g_1 !!== _s_t_r_i_n_g_2
              True if the strings are not equal.

       _s_t_r_i_n_g_1 << _s_t_r_i_n_g_2
              True if _s_t_r_i_n_g_1 sorts before _s_t_r_i_n_g_2 lexicographically.

       _s_t_r_i_n_g_1 >> _s_t_r_i_n_g_2
              True if _s_t_r_i_n_g_1 sorts after _s_t_r_i_n_g_2 lexicographically.

       _a_r_g_1 OOPP _a_r_g_2
              OOPP  is one of --eeqq, --nnee, --lltt, --llee, --ggtt, or --ggee.  These arithmetic
              binary operators return true if _a_r_g_1 is equal to, not equal  to,
              less  than, less than or equal to, greater than, or greater than
              or equal to _a_r_g_2, respectively.  _A_r_g_1 and _a_r_g_2 may  be  positive
              or  negative  integers.  When used with the [[[[ command, _A_r_g_1 and
              _A_r_g_2 are evaluated as  arithmetic  expressions  (see  AARRIITTHHMMEETTIICC
              EEVVAALLUUAATTIIOONN above).

SSIIMMPPLLEE CCOOMMMMAANNDD EEXXPPAANNSSIIOONN
       When a simple command is executed, the shell performs the following ex-
       pansions,  assignments,  and  redirections,  from left to right, in the
       following order.

       1.     The words that the parser has  marked  as  variable  assignments
              (those  preceding  the  command name) and redirections are saved
              for later processing.

       2.     The words that are not variable assignments or redirections  are
              expanded.   If  any words remain after expansion, the first word
              is taken to be the name of the command and the  remaining  words
              are the arguments.

       3.     Redirections are performed as described above under RREEDDIIRREECCTTIIOONN.

       4.     The text after the == in each variable assignment undergoes tilde
              expansion, parameter expansion, command substitution, arithmetic
              expansion,  and quote removal before being assigned to the vari-
              able.

       If no command name results, the variable assignments affect the current
       shell environment.  In the case of such a command  (one  that  consists
       only  of assignment statements and redirections), assignment statements
       are performed before redirections.  Otherwise, the variables are  added
       to  the  environment of the executed command and do not affect the cur-
       rent shell environment.  If any of the assignments attempts to assign a
       value to a readonly variable, an error occurs, and  the  command  exits
       with a non-zero status.

       If  no command name results, redirections are performed, but do not af-
       fect the current shell environment.  A  redirection  error  causes  the
       command to exit with a non-zero status.

       If  there is a command name left after expansion, execution proceeds as
       described below.  Otherwise, the command exits.  If one of  the  expan-
       sions  contained a command substitution, the exit status of the command
       is the exit status of the  last  command  substitution  performed.   If
       there were no command substitutions, the command exits with a status of
       zero.

CCOOMMMMAANNDD EEXXEECCUUTTIIOONN
       After  a  command  has been split into words, if it results in a simple
       command and an optional list of arguments, the shell performs the  fol-
       lowing actions.

       If  the  command name contains no slashes, the shell attempts to locate
       it.  If there exists a shell function by that name,  that  function  is
       invoked  as described above in FFUUNNCCTTIIOONNSS.  If the name does not match a
       function, the shell searches for it in the list of shell builtins.   If
       a match is found, that builtin is invoked.

       If  the name is neither a shell function nor a builtin, and contains no
       slashes, bbaasshh searches each element of the PPAATTHH for  a  directory  con-
       taining an executable file by that name.  BBaasshh uses a hash table to re-
       member  the  full  pathnames  of executable files (see hhaasshh under SSHHEELLLL
       BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  A full search of the directories in  PPAATTHH  is
       performed  only  if the command is not found in the hash table.  If the
       search is unsuccessful, the shell searches for a defined shell function
       named ccoommmmaanndd__nnoott__ffoouunndd__hhaannddllee.  If that function exists, it is invoked
       in a separate execution environment with the original command  and  the
       original  command's arguments as its arguments, and the function's exit
       status becomes the exit status of that subshell.  If that  function  is
       not defined, the shell prints an error message and returns an exit sta-
       tus of 127.

       If  the  search  is  successful, or if the command name contains one or
       more slashes, the shell executes the named program in a separate execu-
       tion environment.  Argument 0 is set to the name given, and the remain-
       ing arguments to the command are set to the arguments given, if any.

       If this execution fails because the file is not in  executable  format,
       and  the file is not a directory, it is assumed to be a _s_h_e_l_l _s_c_r_i_p_t, a
       file containing shell commands, and the shell creates a new instance of
       itself to execute it.  This subshell reinitializes itself, so that  the
       effect is as if a new shell had been invoked to handle the script, with
       the  exception  that the locations of commands remembered by the parent
       (see hhaasshh below under SSHHEELLLL  BBUUIILLTTIINN  CCOOMMMMAANNDDSS)  are  retained  by  the
       child.

       If  the program is a file beginning with ##!!, the remainder of the first
       line specifies an interpreter for the program.  The shell executes  the
       specified interpreter on operating systems that do not handle this exe-
       cutable format themselves.  The arguments to the interpreter consist of
       a  single optional argument following the interpreter name on the first
       line of the program, followed by the name of the program,  followed  by
       the command arguments, if any.

CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT
       The  shell  has an _e_x_e_c_u_t_i_o_n _e_n_v_i_r_o_n_m_e_n_t, which consists of the follow-
       ing:

       +o      open files inherited by the shell at invocation, as modified  by
              redirections supplied to the eexxeecc builtin

       +o      the  current  working directory as set by ccdd, ppuusshhdd, or ppooppdd, or
              inherited by the shell at invocation

       +o      the file creation mode mask as set by uummaasskk  or  inherited  from
              the shell's parent

       +o      current traps set by ttrraapp

       +o      shell parameters that are set by variable assignment or with sseett
              or inherited from the shell's parent in the environment

       +o      shell  functions  defined during execution or inherited from the
              shell's parent in the environment

       +o      options enabled at invocation (either by default  or  with  com-
              mand-line arguments) or by sseett

       +o      options enabled by sshhoopptt

       +o      shell aliases defined with aalliiaass

       +o      various  process  IDs,  including  those of background jobs, the
              value of $$$$, and the value of PPPPIIDD

       When a simple command other than a builtin or shell function is  to  be
       executed,  it  is invoked in a separate execution environment that con-
       sists of the following.  Unless otherwise noted, the values are  inher-
       ited from the shell.

       +o      the  shell's  open  files,  plus any modifications and additions
              specified by redirections to the command

       +o      the current working directory

       +o      the file creation mode mask

       +o      shell variables and functions  marked  for  export,  along  with
              variables exported for the command, passed in the environment

       +o      traps caught by the shell are reset to the values inherited from
              the shell's parent, and traps ignored by the shell are ignored

       A  command  invoked  in  this  separate  environment  cannot affect the
       shell's execution environment.

       A _s_u_b_s_h_e_l_l is a copy of the shell process.

       Command substitution, commands grouped with parentheses, and  asynchro-
       nous commands are invoked in a subshell environment that is a duplicate
       of the shell environment, except that traps caught by the shell are re-
       set  to  the values that the shell inherited from its parent at invoca-
       tion.  Builtin commands that are invoked as part of a pipeline are also
       executed in a subshell environment.  Changes made to the subshell envi-
       ronment cannot affect the shell's execution environment.

       When the shell is in _p_o_s_i_x _m_o_d_e, subshells spawned to  execute  command
       substitutions  inherit  the  value  of  the --ee option from their parent
       shell.  When not in _p_o_s_i_x _m_o_d_e, bbaasshh clears the --ee option in such  sub-
       shells.   See the description of the iinnhheerriitt__eerrrreexxiitt shell option below
       for how to control this behavior when not in posix mode.

       If a command is followed by a && and job control is not active, the  de-
       fault standard input for the command is the empty file _/_d_e_v_/_n_u_l_l.  Oth-
       erwise,  the invoked command inherits the file descriptors of the call-
       ing shell as modified by redirections.

EENNVVIIRROONNMMEENNTT
       When a program is invoked it is given an array of  strings  called  the
       _e_n_v_i_r_o_n_m_e_n_t.   This  is  a  list  of  _n_a_m_e-_v_a_l_u_e  pairs,  of  the  form
       _n_a_m_e=_v_a_l_u_e.

       The shell provides several ways to manipulate the environment.  On  in-
       vocation,  the  shell scans its own environment and creates a parameter
       for each name found, automatically  marking  it  for  _e_x_p_o_r_t  to  child
       processes.   Executed commands inherit the environment.  The eexxppoorrtt and
       ddeeccllaarree --xx commands allow parameters and functions to be added  to  and
       deleted from the environment.  If the value of a parameter in the envi-
       ronment is modified, the new value becomes part of the environment, re-
       placing  the  old.   The  environment inherited by any executed command
       consists of the shell's initial environment, whose values may be  modi-
       fied  in  the  shell, less any pairs removed by the uunnsseett command, plus
       any additions via the eexxppoorrtt and ddeeccllaarree --xx commands.

       The environment for any _s_i_m_p_l_e _c_o_m_m_a_n_d or  function  may  be  augmented
       temporarily  by  prefixing  it with parameter assignments, as described
       above in PPAARRAAMMEETTEERRSS.  These assignment statements affect only the envi-
       ronment seen by that command.

       If the --kk option is set (see the sseett builtin command below),  then  _a_l_l
       parameter  assignments are placed in the environment for a command, not
       just those that precede the command name.

       When bbaasshh invokes an external command, the variable __  is  set  to  the
       full filename of the command and passed to that command in its environ-
       ment.

EEXXIITT SSTTAATTUUSS
       The  exit  status  of  an executed command is the value returned by the
       _w_a_i_t_p_i_d system call or equivalent function.  Exit statuses fall between
       0 and 255, though, as explained below, the shell may use  values  above
       125 specially.  Exit statuses from shell builtins and compound commands
       are also limited to this range.  Under certain circumstances, the shell
       will use special values to indicate specific failure modes.

       For the shell's purposes, a command which exits with a zero exit status
       has  succeeded.   An exit status of zero indicates success.  A non-zero
       exit status indicates failure.  When a command terminates  on  a  fatal
       signal _N, bbaasshh uses the value of 128+_N as the exit status.

       If  a command is not found, the child process created to execute it re-
       turns a status of 127.  If a command is found but  is  not  executable,
       the return status is 126.

       If a command fails because of an error during expansion or redirection,
       the exit status is greater than zero.

       Shell  builtin  commands return a status of 0 (_t_r_u_e) if successful, and
       non-zero (_f_a_l_s_e) if an error occurs while they execute.   All  builtins
       return  an  exit status of 2 to indicate incorrect usage, generally in-
       valid options or missing arguments.

       The exit status of the last command is available in the special parame-
       ter $?.

       BBaasshh itself returns the exit status of the last command  executed,  un-
       less  a  syntax  error  occurs,  in which case it exits with a non-zero
       value.  See also the eexxiitt builtin command below.

SSIIGGNNAALLSS
       When bbaasshh is interactive, in the  absence  of  any  traps,  it  ignores
       SSIIGGTTEERRMM (so that kkiillll 00 does not kill an interactive shell), and SSIIGGIINNTT
       is  caught and handled (so that the wwaaiitt builtin is interruptible).  In
       all cases, bbaasshh ignores SSIIGGQQUUIITT.  If job control is in effect, bbaasshh ig-
       nores SSIIGGTTTTIINN, SSIIGGTTTTOOUU, and SSIIGGTTSSTTPP.

       Non-builtin commands run by bbaasshh have signal handlers set to the values
       inherited by the shell from its parent.  When job control is not in ef-
       fect, asynchronous commands ignore SSIIGGIINNTT and SSIIGGQQUUIITT  in  addition  to
       these  inherited handlers.  Commands run as a result of command substi-
       tution ignore the keyboard-generated job control signals SSIIGGTTTTIINN, SSIIGGTT--
       TTOOUU, and SSIIGGTTSSTTPP.

       The shell exits by default upon receipt of a SSIIGGHHUUPP.   Before  exiting,
       an  interactive  shell  resends  the  SSIIGGHHUUPP  to  all  jobs, running or
       stopped.  Stopped jobs are sent SSIIGGCCOONNTT to ensure that they receive the
       SSIIGGHHUUPP.  To prevent the shell from sending the signal to  a  particular
       job,  it  should be removed from the jobs table with the ddiissoowwnn builtin
       (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) or marked to not receive SSIIGGHHUUPP  us-
       ing ddiissoowwnn --hh.

       If  the  hhuuppoonneexxiitt  shell  option has been set with sshhoopptt, bbaasshh sends a
       SSIIGGHHUUPP to all jobs when an interactive login shell exits.

       If bbaasshh is waiting for a command to complete and receives a signal  for
       which a trap has been set, the trap will not be executed until the com-
       mand  completes.   When bbaasshh is waiting for an asynchronous command via
       the wwaaiitt builtin, the reception of a signal for which a trap  has  been
       set will cause the wwaaiitt builtin to return immediately with an exit sta-
       tus greater than 128, immediately after which the trap is executed.

       When  job  control is not enabled, and bbaasshh is waiting for a foreground
       command to complete, the shell receives keyboard-generated signals such
       as SSIIGGIINNTT (usually generated by ^^CC) that users commonly intend to  send
       to that command.  This happens because the shell and the command are in
       the  same  process  group  as  the terminal, and ^^CC sends SSIIGGIINNTT to all
       processes in that process group.

       When bbaasshh is running without job control enabled  and  receives  SSIIGGIINNTT
       while  waiting for a foreground command, it waits until that foreground
       command terminates and then decides what to do about the SSIIGGIINNTT:

       1.     If the command terminates due to the SSIIGGIINNTT, bbaasshh concludes that
              the user meant to end the entire script, and acts on the  SSIIGGIINNTT
              (e.g., by running a SSIIGGIINNTT trap or exiting itself);

       2.     If  the  command  does  not terminate due to SSIIGGIINNTT, the program
              handled the SSIIGGIINNTT itself and did not treat it as a  fatal  sig-
              nal.   In  that case, bbaasshh does not treat SSIIGGIINNTT as a fatal sig-
              nal, either, instead assuming that the SSIIGGIINNTT was used  as  part
              of  the program's normal operation (e.g., emacs uses it to abort
              editing commands) or deliberately discarded.  However, bbaasshh will
              run any trap set on SSIIGGIINNTT, as it does with  any  other  trapped
              signal  it  receives while it is waiting for the foreground com-
              mand to complete, for compatibility.

JJOOBB CCOONNTTRROOLL
       _J_o_b _c_o_n_t_r_o_l refers to the ability to selectively stop (_s_u_s_p_e_n_d) the ex-
       ecution of processes and continue (_r_e_s_u_m_e) their execution at  a  later
       point.   A  user typically employs this facility via an interactive in-
       terface supplied jointly by the operating system kernel's terminal dri-
       ver and bbaasshh.

       The shell associates a _j_o_b with each pipeline.  It  keeps  a  table  of
       currently  executing  jobs,  which may be listed with the jjoobbss command.
       When bbaasshh starts a job asynchronously (in the _b_a_c_k_g_r_o_u_n_d), it prints  a
       line that looks like:

              [1] 25647

       indicating that this job is job number 1 and that the process ID of the
       last process in the pipeline associated with this job is 25647.  All of
       the  processes  in a single pipeline are members of the same job.  BBaasshh
       uses the _j_o_b abstraction as the basis for job control.

       To facilitate the implementation of the user interface to job  control,
       the operating system maintains the notion of a _c_u_r_r_e_n_t _t_e_r_m_i_n_a_l _p_r_o_c_e_s_s
       _g_r_o_u_p _I_D.  Members of this process group (processes whose process group
       ID is equal to the current terminal process group ID) receive keyboard-
       generated  signals  such  as SSIIGGIINNTT.  These processes are said to be in
       the _f_o_r_e_g_r_o_u_n_d.  _B_a_c_k_g_r_o_u_n_d processes are those whose process group  ID
       differs from the terminal's; such processes are immune to keyboard-gen-
       erated signals.  Only foreground processes are allowed to read from or,
       if  the  user  so  specifies with "stty tostop", write to the terminal.
       Background processes which attempt to read from (write to when "tostop"
       is in effect) the terminal are sent a SSIIGGTTTTIINN ((SSIIGGTTTTOOUU)) signal  by  the
       kernel's terminal driver, which, unless caught, suspends the process.

       If  the operating system on which bbaasshh is running supports job control,
       bbaasshh contains facilities to use it.  Typing the _s_u_s_p_e_n_d character (typ-
       ically ^^ZZ, Control-Z) while a process is running causes that process to
       be stopped and returns control to bbaasshh.   Typing  the  _d_e_l_a_y_e_d  _s_u_s_p_e_n_d
       character  (typically  ^^YY,  Control-Y) causes the process to be stopped
       when it attempts to read input from the terminal, and control to be re-
       turned to bbaasshh.  The user may then manipulate the state  of  this  job,
       using  the  bbgg command to continue it in the background, the ffgg command
       to continue it in the foreground, or the kkiillll command to kill it.  A ^^ZZ
       takes effect immediately, and has the additional side effect of causing
       pending output and typeahead to be discarded.

       There are a number of ways to refer to a job in the shell.  The charac-
       ter %% introduces a job specification (_j_o_b_s_p_e_c).  Job number  _n  may  be
       referred to as %%nn.  A job may also be referred to using a prefix of the
       name used to start it, or using a substring that appears in its command
       line.   For example, %%ccee refers to a stopped job whose command name be-
       gins with ccee.  If a prefix matches more than one job, bbaasshh  reports  an
       error.  Using %%??ccee, on the other hand, refers to any job containing the
       string  ccee in its command line.  If the substring matches more than one
       job, bbaasshh reports an error.  The symbols %%%% and %%++ refer to the shell's
       notion of the _c_u_r_r_e_n_t _j_o_b, which is the last job stopped while  it  was
       in  the  foreground or started in the background.  The _p_r_e_v_i_o_u_s _j_o_b may
       be referenced using %%--.  If there is only a single job, %%++ and  %%--  can
       both be used to refer to that job.  In output pertaining to jobs (e.g.,
       the output of the jjoobbss command), the current job is always flagged with
       a  ++,  and the previous job with a --.  A single % (with no accompanying
       job specification) also refers to the current job.

       Simply naming a job can be used to bring it into the foreground: %%11  is
       a  synonym  for  "fg  %1",  bringing job 1 from the background into the
       foreground.  Similarly, "%1 &" resumes job 1 in the background, equiva-
       lent to "bg %1".

       The shell learns immediately whenever a job changes  state.   Normally,
       bbaasshh waits until it is about to print a prompt before reporting changes
       in  a  job's status so as to not interrupt any other output.  If the --bb
       option to the sseett builtin command is enabled, bbaasshh reports such changes
       immediately.  Any trap on SSIIGGCCHHLLDD is executed for each child  that  ex-
       its.

       If  an  attempt to exit bbaasshh is made while jobs are stopped (or, if the
       cchheecckkjjoobbss shell option has been enabled using the sshhoopptt  builtin,  run-
       ning), the shell prints a warning message, and, if the cchheecckkjjoobbss option
       is  enabled,  lists  the jobs and their statuses.  The jjoobbss command may
       then be used to inspect their status.  If a second attempt to  exit  is
       made  without  an intervening command, the shell does not print another
       warning, and any stopped jobs are terminated.

       When the shell is waiting for a job or process using the wwaaiitt  builtin,
       and  job  control  is  enabled,  wwaaiitt  will return when the job changes
       state. The --ff option causes wwaaiitt to wait until the job or process  ter-
       minates before returning.

PPRROOMMPPTTIINNGG
       When executing interactively, bbaasshh displays the primary prompt PPSS11 when
       it  is  ready  to  read a command, and the secondary prompt PPSS22 when it
       needs more input to complete a command.  BBaasshh  displays  PPSS00  after  it
       reads  a  command  but  before  executing it.  BBaasshh displays PPSS44 as de-
       scribed above before tracing each command when the  --xx  option  is  en-
       abled.   BBaasshh allows these prompt strings to be customized by inserting
       a number of backslash-escaped special characters that  are  decoded  as
       follows:
              \\aa     an ASCII bell character (07)
              \\dd     the  date  in "Weekday Month Date" format (e.g., "Tue May
                     26")
              \\DD{{_f_o_r_m_a_t}}
                     the _f_o_r_m_a_t is passed to _s_t_r_f_t_i_m_e(3) and the result is in-
                     serted into the prompt string; an empty _f_o_r_m_a_t results in
                     a locale-specific time representation.   The  braces  are
                     required
              \\ee     an ASCII escape character (033)
              \\hh     the hostname up to the first "."
              \\HH     the hostname
              \\jj     the number of jobs currently managed by the shell
              \\ll     the basename of the shell's terminal device name
              \\nn     newline
              \\rr     carriage return
              \\ss     the  name  of  the shell, the basename of $$00 (the portion
                     following the final slash)
              \\tt     the current time in 24-hour HH:MM:SS format
              \\TT     the current time in 12-hour HH:MM:SS format
              \\@@     the current time in 12-hour am/pm format
              \\AA     the current time in 24-hour HH:MM format
              \\uu     the username of the current user
              \\vv     the version of bbaasshh (e.g., 2.00)
              \\VV     the release of bbaasshh, version + patch level (e.g., 2.00.0)
              \\ww     the value of the PPWWDD shell variable  ($$PPWWDD),  with  $$HHOOMMEE
                     abbreviated   with   a  tilde  (uses  the  value  of  the
                     PPRROOMMPPTT__DDIIRRTTRRIIMM variable)
              \\WW     the basename of $$PPWWDD, with $$HHOOMMEE abbreviated with a tilde
              \\!!     the history number of this command
              \\##     the command number of this command
              \\$$     if the effective UID is 0, a ##, otherwise a $$
              \\_n_n_n   the character corresponding to the octal number _n_n_n
              \\\\     a backslash
              \\[[     begin a sequence of non-printing characters, which  could
                     be  used  to  embed  a terminal control sequence into the
                     prompt
              \\]]     end a sequence of non-printing characters

       The command number and the history number are  usually  different:  the
       history  number of a command is its position in the history list, which
       may include commands restored from the history file  (see  HHIISSTTOORRYY  be-
       low),  while the command number is the position in the sequence of com-
       mands executed during the current shell session.  After the  string  is
       decoded,  it is expanded via parameter expansion, command substitution,
       arithmetic expansion, and quote removal, subject to the  value  of  the
       pprroommppttvvaarrss shell option (see the description of the sshhoopptt command under
       SSHHEELLLL  BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  This can have unwanted side effects if
       escaped portions of the string appear within  command  substitution  or
       contain characters special to word expansion.

RREEAADDLLIINNEE
       This  is  the library that handles reading input when using an interac-
       tive shell, unless the ----nnooeeddiittiinngg option is given at shell invocation.
       Line editing is also used when using the --ee option to the rreeaadd builtin.
       By default, the line editing commands are similar to those of Emacs.  A
       vi-style line editing interface is also available.  Line editing can be
       enabled at any time using the --oo eemmaaccss or --oo  vvii  options  to  the  sseett
       builtin  (see  SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  To turn off line editing
       after the shell is running, use the ++oo eemmaaccss or ++oo vvii  options  to  the
       sseett builtin.

   RReeaaddlliinnee NNoottaattiioonn
       In this section, the Emacs-style notation is used to denote keystrokes.
       Control  keys  are  denoted by C-_k_e_y, e.g., C-n means Control-N.  Simi-
       larly, _m_e_t_a keys are denoted by M-_k_e_y, so M-x means Meta-X.   (On  key-
       boards  without a _m_e_t_a key, M-_x means ESC _x, i.e., press the Escape key
       then the _x key.  This makes ESC the _m_e_t_a _p_r_e_f_i_x.  The combination M-C-_x
       means ESC-Control-_x, or press the Escape key then hold the Control  key
       while pressing the _x key.)

       Readline commands may be given numeric _a_r_g_u_m_e_n_t_s, which normally act as
       a  repeat  count.   Sometimes,  however, it is the sign of the argument
       that is significant.  Passing a negative argument  to  a  command  that
       acts  in the forward direction (e.g., kkiillll--lliinnee) causes that command to
       act in a backward direction.  Commands whose  behavior  with  arguments
       deviates from this are noted below.

       When  a command is described as _k_i_l_l_i_n_g text, the text deleted is saved
       for possible future retrieval (_y_a_n_k_i_n_g).  The killed text is saved in a
       _k_i_l_l _r_i_n_g.  Consecutive kills cause the text to be accumulated into one
       unit, which can be yanked all at once.  Commands which do not kill text
       separate the chunks of text on the kill ring.

   RReeaaddlliinnee IInniittiiaalliizzaattiioonn
       Readline is customized by putting commands in  an  initialization  file
       (the  _i_n_p_u_t_r_c  file).  The name of this file is taken from the value of
       the IINNPPUUTTRRCC variable.  If that variable is unset, the default is _~_/_._i_n_-
       _p_u_t_r_c.  If that file  does not exist or cannot be  read,  the  ultimate
       default  is  _/_e_t_c_/_i_n_p_u_t_r_c.   When a program which uses the readline li-
       brary starts up, the initialization file is read, and the key  bindings
       and  variables  are set.  There are only a few basic constructs allowed
       in the readline initialization file.  Blank lines are  ignored.   Lines
       beginning  with  a  ##  are comments.  Lines beginning with a $$ indicate
       conditional constructs.  Other lines denote key bindings  and  variable
       settings.

       The  default  key-bindings  may be changed with an _i_n_p_u_t_r_c file.  Other
       programs that use this library may add their own commands and bindings.

       For example, placing

              M-Control-u: universal-argument
       or
              C-Meta-u: universal-argument

       into the _i_n_p_u_t_r_c would make M-C-u execute the readline command  _u_n_i_v_e_r_-
       _s_a_l_-_a_r_g_u_m_e_n_t.

       The  following  symbolic  character  names are recognized: _R_U_B_O_U_T, _D_E_L,
       _E_S_C, _L_F_D, _N_E_W_L_I_N_E, _R_E_T, _R_E_T_U_R_N, _S_P_C, _S_P_A_C_E, and _T_A_B.

       In addition to command names, readline allows keys to  be  bound  to  a
       string that is inserted when the key is pressed (a _m_a_c_r_o).

   RReeaaddlliinnee KKeeyy BBiinnddiinnggss
       The  syntax for controlling key bindings in the _i_n_p_u_t_r_c file is simple.
       All that is required is the name of the command or the text of a  macro
       and a key sequence to which it should be bound.  The name may be speci-
       fied in one of two ways: as a symbolic key name, possibly with _M_e_t_a_- or
       _C_o_n_t_r_o_l_- prefixes, or as a key sequence.

       When using the form kkeeyynnaammee:_f_u_n_c_t_i_o_n_-_n_a_m_e or _m_a_c_r_o, _k_e_y_n_a_m_e is the name
       of a key spelled out in English.  For example:

              Control-u: universal-argument
              Meta-Rubout: backward-kill-word
              Control-o: "> output"

       In  the above example, _C_-_u is bound to the function uunniivveerrssaall--aarrgguummeenntt,
       _M_-_D_E_L is bound to the function bbaacckkwwaarrdd--kkiillll--wwoorrdd, and _C_-_o is bound  to
       run  the macro expressed on the right hand side (that is, to insert the
       text "> output" into the line).

       In the second form, ""kkeeyysseeqq"":_f_u_n_c_t_i_o_n_-_n_a_m_e  or  _m_a_c_r_o,  kkeeyysseeqq  differs
       from  kkeeyynnaammee above in that strings denoting an entire key sequence may
       be specified by placing the sequence within double  quotes.   Some  GNU
       Emacs  style  key escapes can be used, as in the following example, but
       the symbolic character names are not recognized.

              "\C-u": universal-argument
              "\C-x\C-r": re-read-init-file
              "\e[11~": "Function Key 1"

       In this example, _C_-_u is again bound to the function uunniivveerrssaall--aarrgguummeenntt.
       _C_-_x _C_-_r is bound to the function rree--rreeaadd--iinniitt--ffiillee, and _E_S_C _[ _1 _1 _~  is
       bound to insert the text "Function Key 1".

       The full set of GNU Emacs style escape sequences is
              \\CC--    control prefix
              \\MM--    meta prefix
              \\ee     an escape character
              \\\\     backslash
              \\""     literal "
              \\''     literal '

       In  addition  to  the GNU Emacs style escape sequences, a second set of
       backslash escapes is available:
              \\aa     alert (bell)
              \\bb     backspace
              \\dd     delete
              \\ff     form feed
              \\nn     newline
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\_n_n_n   the eight-bit character whose value is  the  octal  value
                     _n_n_n (one to three digits)
              \\xx_H_H   the  eight-bit  character  whose value is the hexadecimal
                     value _H_H (one or two hex digits)

       When entering the text of a macro, single or double quotes must be used
       to indicate a macro definition.  Unquoted text is assumed to be a func-
       tion name.  In the macro body, the backslash  escapes  described  above
       are  expanded.   Backslash  will quote any other character in the macro
       text, including " and '.

       BBaasshh allows the current readline key bindings to be displayed or  modi-
       fied  with  the bbiinndd builtin command.  The editing mode may be switched
       during interactive use by using the --oo option to the sseett  builtin  com-
       mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

   RReeaaddlliinnee VVaarriiaabblleess
       Readline has variables that can be used to further customize its behav-
       ior.  A variable may be set in the _i_n_p_u_t_r_c file with a statement of the
       form

              sseett _v_a_r_i_a_b_l_e_-_n_a_m_e _v_a_l_u_e
       or using the bbiinndd builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

       Except  where  noted,  readline variables can take the values OOnn or OOffff
       (without regard to case).  Unrecognized  variable  names  are  ignored.
       When readline reads a variable value, empty or null values, "on" (case-
       insensitive),  and  "1"  are  equivalent  to  OOnn.  All other values are
       equivalent to OOffff.  The variables and their default values are:

       aaccttiivvee--rreeggiioonn--ssttaarrtt--ccoolloorr
              A string variable that controls the text  color  and  background
              when  displaying the text in the active region (see the descrip-
              tion of eennaabbllee--aaccttiivvee--rreeggiioonn below).  This string must not  take
              up any physical character positions on the display, so it should
              consist  only of terminal escape sequences.  It is output to the
              terminal before displaying the text in the active region.   This
              variable  is  reset  to  the default value whenever the terminal
              type changes.  The default value is the  string  that  puts  the
              terminal  in standout mode, as obtained from the terminal's ter-
              minfo description.  A sample value might be "\e[01;33m".
       aaccttiivvee--rreeggiioonn--eenndd--ccoolloorr
              A string  variable  that  "undoes"  the  effects  of  aaccttiivvee--rree--
              ggiioonn--ssttaarrtt--ccoolloorr  and restores "normal" terminal display appear-
              ance after displaying text in the active  region.   This  string
              must  not  take  up any physical character positions on the dis-
              play, so it should consist only of  terminal  escape  sequences.
              It  is  output  to the terminal after displaying the text in the
              active region.  This variable is  reset  to  the  default  value
              whenever  the  terminal  type changes.  The default value is the
              string that restores the terminal from  standout  mode,  as  ob-
              tained from the terminal's terminfo description.  A sample value
              might be "\e[0m".
       bbeellll--ssttyyllee ((aauuddiibbllee))
              Controls  what  happens when readline wants to ring the terminal
              bell.  If set to nnoonnee, readline never rings the bell.  If set to
              vviissiibbllee, readline uses a visible bell if one is  available.   If
              set to aauuddiibbllee, readline attempts to ring the terminal's bell.
       bbiinndd--ttttyy--ssppeecciiaall--cchhaarrss ((OOnn))
              If  set  to OOnn (the default), readline attempts to bind the con-
              trol  characters that are treated specially by the kernel's ter-
              minal driver to their readline equivalents.  These override  the
              default  readline  bindings described here.  Type "stty -a" at a
              bbaasshh prompt to see your current terminal settings, including the
              special control characters (usually cccchhaarrss).
       bblliinnkk--mmaattcchhiinngg--ppaarreenn ((OOffff))
              If set to OOnn, readline attempts to briefly move the cursor to an
              opening parenthesis when a closing parenthesis is inserted.
       ccoolloorreedd--ccoommpplleettiioonn--pprreeffiixx ((OOffff))
              If set to OOnn, when listing completions,  readline  displays  the
              common prefix of the set of possible completions using a differ-
              ent  color.   The  color definitions are taken from the value of
              the LLSS__CCOOLLOORRSS environment variable.  If there is a color defini-
              tion in $$LLSS__CCOOLLOORRSS for the custom suffix  "readline-colored-com-
              pletion-prefix",  readline uses this color for the common prefix
              instead of its default.
       ccoolloorreedd--ssttaattss ((OOffff))
              If set to OOnn, readline displays possible completions using  dif-
              ferent  colors  to  indicate their file type.  The color defini-
              tions are taken from the  value  of  the  LLSS__CCOOLLOORRSS  environment
              variable.
       ccoommmmeenntt--bbeeggiinn (("##"))
              The  string  that  is  inserted when the readline iinnsseerrtt--ccoommmmeenntt
              command is executed.  This command is bound to MM--## in emacs mode
              and to ## in vi command mode.
       ccoommpplleettiioonn--ddiissppllaayy--wwiiddtthh ((--11))
              The number of screen columns used to  display  possible  matches
              when  performing completion.  The value is ignored if it is less
              than 0 or greater than the terminal screen width.  A value of  0
              will  cause  matches  to be displayed one per line.  The default
              value is -1.
       ccoommpplleettiioonn--iiggnnoorree--ccaassee ((OOffff))
              If set to OOnn, readline performs filename matching and completion
              in a case-insensitive fashion.
       ccoommpplleettiioonn--mmaapp--ccaassee ((OOffff))
              If set to OOnn, and ccoommpplleettiioonn--iiggnnoorree--ccaassee  is  enabled,  readline
              treats  hyphens  (_-) and underscores (__) as equivalent when per-
              forming case-insensitive filename matching and completion.
       ccoommpplleettiioonn--pprreeffiixx--ddiissppllaayy--lleennggtthh ((00))
              The length in characters of the common prefix of a list of  pos-
              sible  completions that is displayed without modification.  When
              set to a value greater than zero, common  prefixes  longer  than
              this  value are replaced with an ellipsis when displaying possi-
              ble completions.
       ccoommpplleettiioonn--qquueerryy--iitteemmss ((110000))
              This determines when the user is queried about viewing the  num-
              ber  of  possible  completions generated by the ppoossssiibbllee--ccoommppllee--
              ttiioonnss command.  It may be set to any integer value greater  than
              or  equal  to  zero.   If  the number of possible completions is
              greater than or equal to the value of  this  variable,  readline
              will  ask whether or not the user wishes to view them; otherwise
              they are simply listed on the  terminal.   A  zero  value  means
              readline should never ask; negative values are treated as zero.
       ccoonnvveerrtt--mmeettaa ((OOnn))
              If  set  to OOnn, readline will convert characters with the eighth
              bit set to an ASCII key sequence by stripping the eighth bit and
              prefixing an escape character (in effect, using  escape  as  the
              _m_e_t_a  _p_r_e_f_i_x).   The  default is _O_n, but readline will set it to
              _O_f_f if the locale contains eight-bit characters.  This  variable
              is  dependent on the LLCC__CCTTYYPPEE locale category, and may change if
              the locale is changed.
       ddiissaabbllee--ccoommpplleettiioonn ((OOffff))
              If set to OOnn, readline will inhibit word completion.  Completion
              characters will be inserted into the line as if  they  had  been
              mapped to sseellff--iinnsseerrtt.
       eecchhoo--ccoonnttrrooll--cchhaarraacctteerrss ((OOnn))
              When  set to OOnn, on operating systems that indicate they support
              it, readline echoes a character corresponding to a signal gener-
              ated from the keyboard.
       eeddiittiinngg--mmooddee ((eemmaaccss))
              Controls whether readline begins with a set of key bindings sim-
              ilar to _E_m_a_c_s or _v_i.  eeddiittiinngg--mmooddee can be set to either eemmaaccss or
              vvii.
       eemmaaccss--mmooddee--ssttrriinngg ((@@))
              If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this  string  is
              displayed immediately before the last line of the primary prompt
              when emacs editing mode is active.  The value is expanded like a
              key  binding,  so the standard set of meta- and control prefixes
              and backslash escape sequences is available.  Use the \1 and  \2
              escapes  to  begin and end sequences of non-printing characters,
              which can be used to embed a terminal control sequence into  the
              mode string.
       eennaabbllee--aaccttiivvee--rreeggiioonn ((OOnn))
              The  _p_o_i_n_t  is the current cursor position, and _m_a_r_k refers to a
              saved cursor position.  The text between the point and  mark  is
              referred  to  as  the  _r_e_g_i_o_n.  When this variable is set to _O_n,
              readline allows certain commands to designate the region as  _a_c_-
              _t_i_v_e.   When  the region is active, readline highlights the text
              in the region using the value of the  aaccttiivvee--rreeggiioonn--ssttaarrtt--ccoolloorr,
              which  defaults to the string that enables the terminal's stand-
              out mode.  The active region shows the text inserted  by  brack-
              eted-paste  and  any matching text found by incremental and non-
              incremental history searches.
       eennaabbllee--bbrraacckkeetteedd--ppaassttee ((OOnn))
              When set to OOnn, readline configures the terminal to insert  each
              paste  into the editing buffer as a single string of characters,
              instead of treating each character as if it had been  read  from
              the keyboard.  This prevents readline from executing any editing
              commands bound to key sequences appearing in the pasted text.
       eennaabbllee--kkeeyyppaadd ((OOffff))
              When set to OOnn, readline will try to enable the application key-
              pad when it is called.  Some systems need this to enable the ar-
              row keys.
       eennaabbllee--mmeettaa--kkeeyy ((OOnn))
              When  set  to  OOnn, readline will try to enable any meta modifier
              key the terminal claims to support when it is called.   On  many
              terminals, the meta key is used to send eight-bit characters.
       eexxppaanndd--ttiillddee ((OOffff))
              If  set  to  OOnn,  tilde expansion is performed when readline at-
              tempts word completion.
       hhiissttoorryy--pprreesseerrvvee--ppooiinntt ((OOffff))
              If set to OOnn, the history code attempts to place  point  at  the
              same  location on each history line retrieved with pprreevviioouuss--hhiiss--
              ttoorryy or nneexxtt--hhiissttoorryy.
       hhiissttoorryy--ssiizzee ((uunnsseett))
              Set the maximum number of history entries saved in  the  history
              list.   If set to zero, any existing history entries are deleted
              and no new entries are saved.  If set to a value less than zero,
              the number of history entries is not limited.  By  default,  the
              number  of  history  entries is set to the value of the HHIISSTTSSIIZZEE
              shell variable.  If an attempt is made to set _h_i_s_t_o_r_y_-_s_i_z_e to  a
              non-numeric value, the maximum number of history entries will be
              set to 500.
       hhoorriizzoonnttaall--ssccrroollll--mmooddee ((OOffff))
              When  set  to  OOnn, makes readline use a single line for display,
              scrolling the input horizontally on a single screen line when it
              becomes longer than the screen width rather than wrapping  to  a
              new  line.   This setting is automatically enabled for terminals
              of height 1.
       iinnppuutt--mmeettaa ((OOffff))
              If set to OOnn, readline will enable eight-bit input (that is,  it
              will not strip the eighth bit from the characters it reads), re-
              gardless  of  what the terminal claims it can support.  The name
              mmeettaa--ffllaagg is a synonym for this variable.  The default  is  _O_f_f,
              but  readline will set it to _O_n if the locale contains eight-bit
              characters.  This variable is dependent on the  LLCC__CCTTYYPPEE  locale
              category, and may change if the locale is changed.
       iisseeaarrcchh--tteerrmmiinnaattoorrss (("CC--[[CC--JJ"))
              The  string  of  characters that should terminate an incremental
              search without subsequently executing the character  as  a  com-
              mand.   If this variable has not been given a value, the charac-
              ters _E_S_C and _C_-_J will terminate an incremental search.
       kkeeyymmaapp ((eemmaaccss))
              Set the current readline keymap.  The set of valid keymap  names
              is  _e_m_a_c_s_,  _e_m_a_c_s_-_s_t_a_n_d_a_r_d_,  _e_m_a_c_s_-_m_e_t_a_, _e_m_a_c_s_-_c_t_l_x_, _v_i_, _v_i_-_c_o_m_-
              _m_a_n_d, and _v_i_-_i_n_s_e_r_t.  _v_i is equivalent to _v_i_-_c_o_m_m_a_n_d;  _e_m_a_c_s  is
              equivalent  to  _e_m_a_c_s_-_s_t_a_n_d_a_r_d.  The default value is _e_m_a_c_s; the
              value of eeddiittiinngg--mmooddee also affects the default keymap.
       kkeeyysseeqq--ttiimmeeoouutt ((550000))
              Specifies the duration _r_e_a_d_l_i_n_e will wait for a  character  when
              reading  an ambiguous key sequence (one that can form a complete
              key sequence using the input read so far, or can take additional
              input to complete a longer key sequence).  If no  input  is  re-
              ceived  within  the  timeout,  _r_e_a_d_l_i_n_e will use the shorter but
              complete key sequence.  The value is specified in  milliseconds,
              so  a value of 1000 means that _r_e_a_d_l_i_n_e will wait one second for
              additional input.  If this variable is set to a value less  than
              or  equal to zero, or to a non-numeric value, _r_e_a_d_l_i_n_e will wait
              until another key is pressed to decide  which  key  sequence  to
              complete.
       mmaarrkk--ddiirreeccttoorriieess ((OOnn))
              If set to OOnn, completed directory names have a slash appended.
       mmaarrkk--mmooddiiffiieedd--lliinneess ((OOffff))
              If  set  to  OOnn,  history lines that have been modified are dis-
              played with a preceding asterisk (**).
       mmaarrkk--ssyymmlliinnkkeedd--ddiirreeccttoorriieess ((OOffff))
              If set to OOnn, completed names which are symbolic links to direc-
              tories have a slash appended (subject to the value  of  mmaarrkk--ddii--
              rreeccttoorriieess).
       mmaattcchh--hhiiddddeenn--ffiilleess ((OOnn))
              This  variable,  when  set to OOnn, forces readline to match files
              whose names begin with a "."   (hidden  files)  when  performing
              filename  completion.   If set to OOffff, the user must include the
              leading "."  in the filename to be completed.
       mmeennuu--ccoommpplleettee--ddiissppllaayy--pprreeffiixx ((OOffff))
              If set to OOnn, menu completion displays the common prefix of  the
              list of possible completions (which may be empty) before cycling
              through the list.
       oouuttppuutt--mmeettaa ((OOffff))
              If  set  to OOnn, readline will display characters with the eighth
              bit set directly rather than as a meta-prefixed escape sequence.
              The default is _O_f_f, but readline will set it to _O_n if the locale
              contains eight-bit characters.  This variable  is  dependent  on
              the  LLCC__CCTTYYPPEE  locale  category, and may change if the locale is
              changed.
       ppaaggee--ccoommpplleettiioonnss ((OOnn))
              If set to OOnn, readline uses an internal _m_o_r_e-like pager to  dis-
              play a screenful of possible completions at a time.
       pprriinntt--ccoommpplleettiioonnss--hhoorriizzoonnttaallllyy ((OOffff))
              If  set  to  OOnn,  readline will display completions with matches
              sorted horizontally in alphabetical order, rather than down  the
              screen.
       rreevveerrtt--aallll--aatt--nneewwlliinnee ((OOffff))
              If  set  to  OOnn, readline will undo all changes to history lines
              before returning when aacccceepptt--lliinnee is executed.  By default, his-
              tory lines may be modified  and  retain  individual  undo  lists
              across calls to rreeaaddlliinnee.
       sseeaarrcchh--iiggnnoorree--ccaassee ((OOffff))
              If  set to OOnn, readline performs incremental and non-incremental
              history list searches in a case-insensitive fashion.
       sshhooww--aallll--iiff--aammbbiigguuoouuss ((OOffff))
              This alters the default behavior of  the  completion  functions.
              If set to OOnn, words which have more than one possible completion
              cause  the  matches  to be listed immediately instead of ringing
              the bell.
       sshhooww--aallll--iiff--uunnmmooddiiffiieedd ((OOffff))
              This alters the default behavior of the completion functions  in
              a fashion similar to sshhooww--aallll--iiff--aammbbiigguuoouuss.  If set to OOnn, words
              which  have more than one possible completion without any possi-
              ble partial completion (the possible completions don't  share  a
              common  prefix)  cause  the matches to be listed immediately in-
              stead of ringing the bell.
       sshhooww--mmooddee--iinn--pprroommpptt ((OOffff))
              If set to OOnn, add a string to the beginning of the prompt  indi-
              cating  the  editing  mode:  emacs, vi command, or vi insertion.
              The mode strings are user-settable (e.g., _e_m_a_c_s_-_m_o_d_e_-_s_t_r_i_n_g).
       sskkiipp--ccoommpplleetteedd--tteexxtt ((OOffff))
              If set to OOnn, this alters the default completion  behavior  when
              inserting  a  single match into the line.  It's only active when
              performing completion in the middle  of  a  word.   If  enabled,
              readline  does  not  insert  characters from the completion that
              match characters after point in the  word  being  completed,  so
              portions of the word following the cursor are not duplicated.
       vvii--ccmmdd--mmooddee--ssttrriinngg ((((ccmmdd))))
              If  the  _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this string is
              displayed immediately before the last line of the primary prompt
              when vi editing mode is active and in command mode.   The  value
              is expanded like a key binding, so the standard set of meta- and
              control  prefixes  and  backslash escape sequences is available.
              Use the \1 and \2 escapes to begin and  end  sequences  of  non-
              printing  characters, which can be used to embed a terminal con-
              trol sequence into the mode string.
       vvii--iinnss--mmooddee--ssttrriinngg ((((iinnss))))
              If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this  string  is
              displayed immediately before the last line of the primary prompt
              when vi editing mode is active and in insertion mode.  The value
              is expanded like a key binding, so the standard set of meta- and
              control  prefixes  and  backslash escape sequences is available.
              Use the \1 and \2 escapes to begin and  end  sequences  of  non-
              printing  characters, which can be used to embed a terminal con-
              trol sequence into the mode string.
       vviissiibbllee--ssttaattss ((OOffff))
              If set to OOnn, a character denoting a file's type as reported  by
              _s_t_a_t(2)  is  appended to the filename when listing possible com-
              pletions.

   RReeaaddlliinnee CCoonnddiittiioonnaall CCoonnssttrruuccttss
       Readline implements a facility similar in  spirit  to  the  conditional
       compilation  features  of  the C preprocessor which allows key bindings
       and variable settings to be performed as the result  of  tests.   There
       are four parser directives used.

       $$iiff    The  $$iiff construct allows bindings to be made based on the edit-
              ing mode, the terminal being  used,  or  the  application  using
              readline.   The text of the test, after any comparison operator,
              extends to the end of the line; unless otherwise noted, no char-
              acters are required to isolate it.

              mmooddee   The mmooddee== form of the  $$iiff  directive  is  used  to  test
                     whether  readline  is  in  emacs or vi mode.  This may be
                     used in conjunction with the sseett kkeeyymmaapp command, for  in-
                     stance,   to  set  bindings  in  the  _e_m_a_c_s_-_s_t_a_n_d_a_r_d  and
                     _e_m_a_c_s_-_c_t_l_x keymaps only if readline is  starting  out  in
                     emacs mode.

              tteerrmm   The  tteerrmm==  form may be used to include terminal-specific
                     key bindings, perhaps to bind the key sequences output by
                     the terminal's function keys.  The word on the right side
                     of the == is tested against both the full name of the ter-
                     minal and the portion of the  terminal  name  before  the
                     first  --.  This allows _s_u_n to match both _s_u_n and _s_u_n_-_c_m_d,
                     for instance.

              vveerrssiioonn
                     The vveerrssiioonn test  may  be  used  to  perform  comparisons
                     against  specific readline versions.  The vveerrssiioonn expands
                     to the current readline version.  The set  of  comparison
                     operators  includes  ==,  (and  ====), !!==, <<==, >>==, <<, and >>.
                     The version number supplied on the right side of the  op-
                     erator  consists  of  a major version number, an optional
                     decimal point, and an optional minor version (e.g., 77..11).
                     If the minor version is omitted, it is assumed to  be  00.
                     The operator may be separated from the string vveerrssiioonn and
                     from the version number argument by whitespace.

              _a_p_p_l_i_c_a_t_i_o_n
                     The _a_p_p_l_i_c_a_t_i_o_n construct is used to include application-
                     specific  settings.   Each program using the readline li-
                     brary sets the _a_p_p_l_i_c_a_t_i_o_n _n_a_m_e,  and  an  initialization
                     file can test for a particular value.  This could be used
                     to  bind key sequences to functions useful for a specific
                     program.  For instance, the following command adds a  key
                     sequence  that  quotes  the  current  or previous word in
                     bbaasshh:

                     $$iiff Bash
                     # Quote the current or previous word
                     "\C-xq": "\eb\"\ef\""
                     $$eennddiiff

              _v_a_r_i_a_b_l_e
                     The _v_a_r_i_a_b_l_e construct provides simple equality tests for
                     readline variables and values.  The permitted  comparison
                     operators  are  _=, _=_=, and _!_=.  The variable name must be
                     separated from the comparison operator by whitespace; the
                     operator may be separated from the  value  on  the  right
                     hand  side  by whitespace.  Both string and boolean vari-
                     ables may be tested. Boolean  variables  must  be  tested
                     against the values _o_n and _o_f_f.

       $$eennddiiff This command, as seen in the previous example, terminates an $$iiff
              command.

       $$eellssee  Commands in this branch of the $$iiff directive are executed if the
              test fails.

       $$iinncclluuddee
              This  directive takes a single filename as an argument and reads
              commands and bindings from that file.  For example, the  follow-
              ing directive would read _/_e_t_c_/_i_n_p_u_t_r_c:

              $$iinncclluuddee  _/_e_t_c_/_i_n_p_u_t_r_c

   SSeeaarrcchhiinngg
       Readline  provides  commands  for searching through the command history
       (see HHIISSTTOORRYY below) for lines containing a specified string.  There are
       two search modes: _i_n_c_r_e_m_e_n_t_a_l and _n_o_n_-_i_n_c_r_e_m_e_n_t_a_l.

       Incremental searches begin before the  user  has  finished  typing  the
       search  string.  As each character of the search string is typed, read-
       line displays the next entry from the history matching the string typed
       so far.  An incremental search requires  only  as  many  characters  as
       needed  to  find  the desired history entry.  The characters present in
       the value of the iisseeaarrcchh--tteerrmmiinnaattoorrss variable are used to terminate  an
       incremental search.  If that variable has not been assigned a value the
       Escape  and  Control-J characters will terminate an incremental search.
       Control-G will abort an incremental search  and  restore  the  original
       line.   When the search is terminated, the history entry containing the
       search string becomes the current line.

       To find other matching entries in the history list, type  Control-S  or
       Control-R  as appropriate.  This will search backward or forward in the
       history for the next entry matching the search  string  typed  so  far.
       Any  other  key sequence bound to a readline command will terminate the
       search and execute that command.  For instance, a _n_e_w_l_i_n_e  will  termi-
       nate the search and accept the line, thereby executing the command from
       the history list.

       Readline remembers the last incremental search string.  If two Control-
       Rs  are  typed without any intervening characters defining a new search
       string, readline uses any remembered search string.

       Non-incremental searches read the entire search string before  starting
       to  search  for matching history lines.  The search string may be typed
       by the user or be part of the contents of the current line.

   RReeaaddlliinnee CCoommmmaanndd NNaammeess
       The following is a list of the names of the commands  and  the  default
       key sequences to which they are bound.  Command names without an accom-
       panying key sequence are unbound by default.  In the following descrip-
       tions,  _p_o_i_n_t refers to the current cursor position, and _m_a_r_k refers to
       a cursor position saved by the sseett--mmaarrkk command.  The text between  the
       point and mark is referred to as the _r_e_g_i_o_n.

   CCoommmmaannddss ffoorr MMoovviinngg
       bbeeggiinnnniinngg--ooff--lliinnee ((CC--aa))
              Move  to  the start of the current line.  This may also be bound
              to the Home key on some keyboards.
       eenndd--ooff--lliinnee ((CC--ee))
              Move to the end of the line.  This may also be bound to the  End
              key on some keyboards.
       ffoorrwwaarrdd--cchhaarr ((CC--ff))
              Move forward a character.
       bbaacckkwwaarrdd--cchhaarr ((CC--bb))
              Move back a character.
       ffoorrwwaarrdd--wwoorrdd ((MM--ff))
              Move forward to the end of the next word.  Words are composed of
              alphanumeric characters (letters and digits).
       bbaacckkwwaarrdd--wwoorrdd ((MM--bb))
              Move  back  to the start of the current or previous word.  Words
              are composed of alphanumeric characters (letters and digits).
       sshheellll--ffoorrwwaarrdd--wwoorrdd
              Move forward to the end of the next word.  Words  are  delimited
              by non-quoted shell metacharacters.
       sshheellll--bbaacckkwwaarrdd--wwoorrdd
              Move  back  to the start of the current or previous word.  Words
              are delimited by non-quoted shell metacharacters.
       pprreevviioouuss--ssccrreeeenn--lliinnee
              Attempt to move point to the same physical screen column on  the
              previous  physical  screen  line. This will not have the desired
              effect if the current readline line does not take up  more  than
              one  physical line or if point is not greater than the length of
              the prompt plus the screen width.
       nneexxtt--ssccrreeeenn--lliinnee
              Attempt to move point to the same physical screen column on  the
              next physical screen line. This will not have the desired effect
              if  the  current  readline  line  does not take up more than one
              physical line or if the length of the current readline  line  is
              not greater than the length of the prompt plus the screen width.
       cclleeaarr--ddiissppllaayy ((MM--CC--ll))
              Clear  the  screen  and,  if possible, the terminal's scrollback
              buffer, then redraw the current line, leaving the  current  line
              at the top of the screen.
       cclleeaarr--ssccrreeeenn ((CC--ll))
              Clear the screen, then redraw the current line, leaving the cur-
              rent  line  at the top of the screen.  With an argument, refresh
              the current line without clearing the screen.
       rreeddrraaww--ccuurrrreenntt--lliinnee
              Refresh the current line.

   CCoommmmaannddss ffoorr MMaanniippuullaattiinngg tthhee HHiissttoorryy
       aacccceepptt--lliinnee ((NNeewwlliinnee,, RReettuurrnn))
              Accept the line regardless of where the cursor is.  If this line
              is non-empty, add it to the history list according to the  state
              of  the HHIISSTTCCOONNTTRROOLL variable.  If the line is a modified history
              line, then restore the history line to its original state.
       pprreevviioouuss--hhiissttoorryy ((CC--pp))
              Fetch the previous command from the history list, moving back in
              the list.
       nneexxtt--hhiissttoorryy ((CC--nn))
              Fetch the next command from the history list, moving forward  in
              the list.
       bbeeggiinnnniinngg--ooff--hhiissttoorryy ((MM--<<))
              Move to the first line in the history.
       eenndd--ooff--hhiissttoorryy ((MM-->>))
              Move  to  the end of the input history, i.e., the line currently
              being entered.
       ooppeerraattee--aanndd--ggeett--nneexxtt ((CC--oo))
              Accept the current line for execution and fetch  the  next  line
              relative  to  the  current line from the history for editing.  A
              numeric argument, if supplied, specifies the  history  entry  to
              use instead of the current line.
       ffeettcchh--hhiissttoorryy
              With  a numeric argument, fetch that entry from the history list
              and make it the current line.  Without an argument, move back to
              the first entry in the history list.
       rreevveerrssee--sseeaarrcchh--hhiissttoorryy ((CC--rr))
              Search backward starting at the current  line  and  moving  "up"
              through  the  history  as  necessary.   This  is  an incremental
              search.
       ffoorrwwaarrdd--sseeaarrcchh--hhiissttoorryy ((CC--ss))
              Search forward starting at the current line  and  moving  "down"
              through  the  history  as  necessary.   This  is  an incremental
              search.
       nnoonn--iinnccrreemmeennttaall--rreevveerrssee--sseeaarrcchh--hhiissttoorryy ((MM--pp))
              Search backward through the history starting at the current line
              using a non-incremental search for  a  string  supplied  by  the
              user.
       nnoonn--iinnccrreemmeennttaall--ffoorrwwaarrdd--sseeaarrcchh--hhiissttoorryy ((MM--nn))
              Search  forward  through  the  history  using  a non-incremental
              search for a string supplied by the user.
       hhiissttoorryy--sseeaarrcchh--bbaacckkwwaarrdd
              Search backward through the history for the string of characters
              between the start of the current line and the point.  This is  a
              non-incremental search.  This may be bound to the Page Up key on
              some keyboards.
       hhiissttoorryy--sseeaarrcchh--ffoorrwwaarrdd
              Search  forward through the history for the string of characters
              between the start of the current line and the point.  This is  a
              non-incremental  search.  This may be bound to the Page Down key
              on some keyboards.
       hhiissttoorryy--ssuubbssttrriinngg--sseeaarrcchh--bbaacckkwwaarrdd
              Search backward through the history for the string of characters
              between the start of the current line and the current cursor po-
              sition (the _p_o_i_n_t).  The search string may match anywhere  in  a
              history line.  This is a non-incremental search.
       hhiissttoorryy--ssuubbssttrriinngg--sseeaarrcchh--ffoorrwwaarrdd
              Search  forward through the history for the string of characters
              between the start of the current line and the point.  The search
              string may match anywhere in a history line.  This is a  non-in-
              cremental search.
       yyaannkk--nntthh--aarrgg ((MM--CC--yy))
              Insert  the  first argument to the previous command (usually the
              second word on the previous line) at point.  With an argument _n,
              insert the _nth word from the previous command (the words in  the
              previous  command  begin  with word 0).  A negative argument in-
              serts the _nth word from the end of the previous  command.   Once
              the  argument _n is computed, the argument is extracted as if the
              "!_n" history expansion had been specified.
       yyaannkk--llaasstt--aarrgg ((MM--..,, MM--__))
              Insert the last argument to the previous command (the last  word
              of the previous history entry).  With a numeric argument, behave
              exactly  like  yyaannkk--nntthh--aarrgg.   Successive calls to yyaannkk--llaasstt--aarrgg
              move back through the history list, inserting the last word  (or
              the  word  specified  by the argument to the first call) of each
              line in turn.  Any numeric argument supplied to these successive
              calls determines the direction to move through the  history.   A
              negative  argument  switches  the  direction through the history
              (back or forward).  The history expansion facilities are used to
              extract the last word, as if the "!$" history expansion had been
              specified.
       sshheellll--eexxppaanndd--lliinnee ((MM--CC--ee))
              Expand the line by performing shell word expansions.  This  per-
              forms alias and history expansion, $$'_s_t_r_i_n_g' and $$"_s_t_r_i_n_g" quot-
              ing,  tilde  expansion, parameter and variable expansion, arith-
              metic expansion, command and process substitution,  word  split-
              ting,  and  quote removal.  An explicit argument suppresses com-
              mand and process substitution.  See HHIISSTTOORRYY EEXXPPAANNSSIIOONN below  for
              a description of history expansion.
       hhiissttoorryy--eexxppaanndd--lliinnee ((MM--^^))
              Perform  history expansion on the current line.  See HHIISSTTOORRYY EEXX--
              PPAANNSSIIOONN below for a description of history expansion.
       mmaaggiicc--ssppaaccee
              Perform history expansion on  the  current  line  and  insert  a
              space.  See HHIISSTTOORRYY EEXXPPAANNSSIIOONN below for a description of history
              expansion.
       aalliiaass--eexxppaanndd--lliinnee
              Perform  alias expansion on the current line.  See AALLIIAASSEESS above
              for a description of alias expansion.
       hhiissttoorryy--aanndd--aalliiaass--eexxppaanndd--lliinnee
              Perform history and alias expansion on the current line.
       iinnsseerrtt--llaasstt--aarrgguummeenntt ((MM--..,, MM--__))
              A synonym for yyaannkk--llaasstt--aarrgg.
       eeddiitt--aanndd--eexxeeccuuttee--ccoommmmaanndd ((CC--xx CC--ee))
              Invoke an editor on the current command line,  and  execute  the
              result as shell commands.  BBaasshh attempts to invoke $$VVIISSUUAALL, $$EEDD--
              IITTOORR, and _e_m_a_c_s as the editor, in that order.

   CCoommmmaannddss ffoorr CChhaannggiinngg TTeexxtt
       _e_n_d_-_o_f_-_f_i_l_e ((uussuuaallllyy CC--dd))
              The  character  indicating  end-of-file  as set, for example, by
              _s_t_t_y(1).  If this character is read when there are no characters
              on the line, and point is at the beginning of the line, readline
              interprets it as the end of input and returns EEOOFF.
       ddeelleettee--cchhaarr ((CC--dd))
              Delete the character at point.  If this function is bound to the
              same character as the tty EEOOFF character, as CC--dd commonly is, see
              above for the effects.
       bbaacckkwwaarrdd--ddeelleettee--cchhaarr ((RRuubboouutt))
              Delete the character behind the cursor.  When  given  a  numeric
              argument, save the deleted text on the kill ring.
       ffoorrwwaarrdd--bbaacckkwwaarrdd--ddeelleettee--cchhaarr
              Delete  the  character under the cursor, unless the cursor is at
              the end of the line, in which case the character behind the cur-
              sor is deleted.
       qquuootteedd--iinnsseerrtt ((CC--qq,, CC--vv))
              Add the next character typed to the line verbatim.  This is  how
              to insert characters like CC--qq, for example.
       ttaabb--iinnsseerrtt ((CC--vv TTAABB))
              Insert a tab character.
       sseellff--iinnsseerrtt ((aa,, bb,, AA,, 11,, !!,, ...))
              Insert the character typed.
       ttrraannssppoossee--cchhaarrss ((CC--tt))
              Drag  the  character  before point forward over the character at
              point, moving point forward as well.  If point is at the end  of
              the  line, then this transposes the two characters before point.
              Negative arguments have no effect.
       ttrraannssppoossee--wwoorrddss ((MM--tt))
              Drag the word before point past the  word  after  point,  moving
              point  over  that  word  as well.  If point is at the end of the
              line, this transposes the last two words on the line.
       uuppccaassee--wwoorrdd ((MM--uu))
              Uppercase the current (or following) word.  With a negative  ar-
              gument, uppercase the previous word, but do not move point.
       ddoowwnnccaassee--wwoorrdd ((MM--ll))
              Lowercase  the current (or following) word.  With a negative ar-
              gument, lowercase the previous word, but do not move point.
       ccaappiittaalliizzee--wwoorrdd ((MM--cc))
              Capitalize the current (or following) word.  With a negative ar-
              gument, capitalize the previous word, but do not move point.
       oovveerrwwrriittee--mmooddee
              Toggle overwrite mode.  With an explicit positive numeric  argu-
              ment, switches to overwrite mode.  With an explicit non-positive
              numeric argument, switches to insert mode.  This command affects
              only  eemmaaccss mode; vvii mode does overwrite differently.  Each call
              to _r_e_a_d_l_i_n_e_(_) starts in insert mode.  In overwrite mode, charac-
              ters bound to sseellff--iinnsseerrtt replace the text at point rather  than
              pushing  the  text  to  the  right.   Characters  bound to bbaacckk--
              wwaarrdd--ddeelleettee--cchhaarr replace  the  character  before  point  with  a
              space.  By default, this command is unbound, but may be bound to
              the Insert key on some keyboards.

   KKiilllliinngg aanndd YYaannkkiinngg
       kkiillll--lliinnee ((CC--kk))
              Kill the text from point to the end of the line.
       bbaacckkwwaarrdd--kkiillll--lliinnee ((CC--xx RRuubboouutt))
              Kill backward to the beginning of the line.
       uunniixx--lliinnee--ddiissccaarrdd ((CC--uu))
              Kill  backward  from  point  to  the beginning of the line.  The
              killed text is saved on the kill-ring.
       kkiillll--wwhhoollee--lliinnee
              Kill all characters on the current line, no matter  where  point
              is.
       kkiillll--wwoorrdd ((MM--dd))
              Kill  from  point  to the end of the current word, or if between
              words, to the end of the next word.   Word  boundaries  are  the
              same as those used by ffoorrwwaarrdd--wwoorrdd.
       bbaacckkwwaarrdd--kkiillll--wwoorrdd ((MM--RRuubboouutt))
              Kill  the  word  behind  point.  Word boundaries are the same as
              those used by bbaacckkwwaarrdd--wwoorrdd.
       sshheellll--kkiillll--wwoorrdd
              Kill from point to the end of the current word,  or  if  between
              words,  to  the  end  of the next word.  Word boundaries are the
              same as those used by sshheellll--ffoorrwwaarrdd--wwoorrdd.
       sshheellll--bbaacckkwwaarrdd--kkiillll--wwoorrdd
              Kill the word behind point.  Word boundaries  are  the  same  as
              those used by sshheellll--bbaacckkwwaarrdd--wwoorrdd.
       uunniixx--wwoorrdd--rruubboouutt ((CC--ww))
              Kill  the  word behind point, using white space as a word bound-
              ary.  The killed text is saved on the kill-ring.
       uunniixx--ffiilleennaammee--rruubboouutt
              Kill the word behind point, using  white  space  and  the  slash
              character  as  the word boundaries.  The killed text is saved on
              the kill-ring.
       ddeelleettee--hhoorriizzoonnttaall--ssppaaccee ((MM--\\))
              Delete all spaces and tabs around point.
       kkiillll--rreeggiioonn
              Kill the text in the current region.
       ccooppyy--rreeggiioonn--aass--kkiillll
              Copy the text in the region to the kill buffer.
       ccooppyy--bbaacckkwwaarrdd--wwoorrdd
              Copy the word before point to the kill buffer.  The word  bound-
              aries are the same as bbaacckkwwaarrdd--wwoorrdd.
       ccooppyy--ffoorrwwaarrdd--wwoorrdd
              Copy  the  word  following  point  to the kill buffer.  The word
              boundaries are the same as ffoorrwwaarrdd--wwoorrdd.
       yyaannkk ((CC--yy))
              Yank the top of the kill ring into the buffer at point.
       yyaannkk--ppoopp ((MM--yy))
              Rotate the kill ring, and yank the new top.  Only works  follow-
              ing yyaannkk or yyaannkk--ppoopp.

   NNuummeerriicc AArrgguummeennttss
       ddiiggiitt--aarrgguummeenntt ((MM--00,, MM--11,, ...,, MM----))
              Add  this digit to the argument already accumulating, or start a
              new argument.  M-- starts a negative argument.
       uunniivveerrssaall--aarrgguummeenntt
              This is another way to specify an argument.  If this command  is
              followed  by one or more digits, optionally with a leading minus
              sign, those digits define the argument.  If the command is  fol-
              lowed by digits, executing uunniivveerrssaall--aarrgguummeenntt again ends the nu-
              meric argument, but is otherwise ignored.  As a special case, if
              this command is immediately followed by a character that is nei-
              ther  a  digit  nor  minus sign, the argument count for the next
              command is multiplied by four.  The argument count is  initially
              one,  so  executing this function the first time makes the argu-
              ment count four, a second time makes the argument count sixteen,
              and so on.

   CCoommpplleettiinngg
       ccoommpplleettee ((TTAABB))
              Attempt to perform completion on the text  before  point.   BBaasshh
              attempts completion treating the text as a variable (if the text
              begins  with  $$), username (if the text begins with ~~), hostname
              (if the text begins with @@), or command (including  aliases  and
              functions) in turn.  If none of these produces a match, filename
              completion is attempted.
       ppoossssiibbllee--ccoommpplleettiioonnss ((MM--??))
              List the possible completions of the text before point.
       iinnsseerrtt--ccoommpplleettiioonnss ((MM--**))
              Insert  all completions of the text before point that would have
              been generated by ppoossssiibbllee--ccoommpplleettiioonnss.
       mmeennuu--ccoommpplleettee
              Similar to ccoommpplleettee, but replaces the word to be completed  with
              a  single match from the list of possible completions.  Repeated
              execution of mmeennuu--ccoommpplleettee steps through the  list  of  possible
              completions,  inserting  each  match in turn.  At the end of the
              list of completions, the bell is rung (subject to the setting of
              bbeellll--ssttyyllee) and the original text is restored.  An argument of _n
              moves _n positions forward in the list of matches; a negative ar-
              gument may be used to move backward through the list.  This com-
              mand is intended to be bound to TTAABB, but is unbound by default.
       mmeennuu--ccoommpplleettee--bbaacckkwwaarrdd
              Identical to mmeennuu--ccoommpplleettee, but moves backward through the  list
              of  possible  completions,  as if mmeennuu--ccoommpplleettee had been given a
              negative argument.  This command is unbound by default.
       ddeelleettee--cchhaarr--oorr--lliisstt
              Deletes the character under the cursor if not at  the  beginning
              or  end  of  the  line (like ddeelleettee--cchhaarr).  If at the end of the
              line, behaves identically to ppoossssiibbllee--ccoommpplleettiioonnss.  This command
              is unbound by default.
       ccoommpplleettee--ffiilleennaammee ((MM--//))
              Attempt filename completion on the text before point.
       ppoossssiibbllee--ffiilleennaammee--ccoommpplleettiioonnss ((CC--xx //))
              List the possible completions of the text before point, treating
              it as a filename.
       ccoommpplleettee--uusseerrnnaammee ((MM--~~))
              Attempt completion on the text before point, treating  it  as  a
              username.
       ppoossssiibbllee--uusseerrnnaammee--ccoommpplleettiioonnss ((CC--xx ~~))
              List the possible completions of the text before point, treating
              it as a username.
       ccoommpplleettee--vvaarriiaabbllee ((MM--$$))
              Attempt  completion  on  the text before point, treating it as a
              shell variable.
       ppoossssiibbllee--vvaarriiaabbllee--ccoommpplleettiioonnss ((CC--xx $$))
              List the possible completions of the text before point, treating
              it as a shell variable.
       ccoommpplleettee--hhoossttnnaammee ((MM--@@))
              Attempt completion on the text before point, treating  it  as  a
              hostname.
       ppoossssiibbllee--hhoossttnnaammee--ccoommpplleettiioonnss ((CC--xx @@))
              List the possible completions of the text before point, treating
              it as a hostname.
       ccoommpplleettee--ccoommmmaanndd ((MM--!!))
              Attempt  completion  on  the text before point, treating it as a
              command name.  Command completion attempts  to  match  the  text
              against   aliases,   reserved   words,  shell  functions,  shell
              builtins, and finally executable filenames, in that order.
       ppoossssiibbllee--ccoommmmaanndd--ccoommpplleettiioonnss ((CC--xx !!))
              List the possible completions of the text before point, treating
              it as a command name.
       ddyynnaammiicc--ccoommpplleettee--hhiissttoorryy ((MM--TTAABB))
              Attempt completion on the text before point, comparing the  text
              against  lines  from  the  history  list for possible completion
              matches.
       ddaabbbbrreevv--eexxppaanndd
              Attempt menu completion on the text before point, comparing  the
              text against lines from the history list for possible completion
              matches.
       ccoommpplleettee--iinnttoo--bbrraacceess ((MM--{{))
              Perform filename completion and insert the list of possible com-
              pletions  enclosed within braces so the list is available to the
              shell (see BBrraaccee EExxppaannssiioonn above).

   KKeeyybbooaarrdd MMaaccrrooss
       ssttaarrtt--kkbbdd--mmaaccrroo ((CC--xx (())
              Begin saving the characters  typed  into  the  current  keyboard
              macro.
       eenndd--kkbbdd--mmaaccrroo ((CC--xx ))))
              Stop saving the characters typed into the current keyboard macro
              and store the definition.
       ccaallll--llaasstt--kkbbdd--mmaaccrroo ((CC--xx ee))
              Re-execute  the last keyboard macro defined, by making the char-
              acters in the macro appear as if typed at the keyboard.
       pprriinntt--llaasstt--kkbbdd--mmaaccrroo (())
              Print the last keyboard macro defined in a format  suitable  for
              the _i_n_p_u_t_r_c file.

   MMiisscceellllaanneeoouuss
       rree--rreeaadd--iinniitt--ffiillee ((CC--xx CC--rr))
              Read  in  the  contents of the _i_n_p_u_t_r_c file, and incorporate any
              bindings or variable assignments found there.
       aabboorrtt ((CC--gg))
              Abort the current editing command and ring the  terminal's  bell
              (subject to the setting of bbeellll--ssttyyllee).
       ddoo--lloowweerrccaassee--vveerrssiioonn ((MM--AA,, MM--BB,, MM--_x,, ...))
              If  the  metafied character _x is uppercase, run the command that
              is bound to the corresponding metafied lowercase character.  The
              behavior is undefined if _x is already lowercase.
       pprreeffiixx--mmeettaa ((EESSCC))
              Metafy the next character typed.  EESSCC ff is equivalent to MMeettaa--ff.
       uunnddoo ((CC--__,, CC--xx CC--uu))
              Incremental undo, separately remembered for each line.
       rreevveerrtt--lliinnee ((MM--rr))
              Undo all changes made to this line.  This is like executing  the
              uunnddoo  command  enough  times  to  return the line to its initial
              state.
       ttiillddee--eexxppaanndd ((MM--&&))
              Perform tilde expansion on the current word.
       sseett--mmaarrkk ((CC--@@,, MM--<<ssppaaccee>>))
              Set the mark to the point.  If a numeric argument  is  supplied,
              the mark is set to that position.
       eexxcchhaannggee--ppooiinntt--aanndd--mmaarrkk ((CC--xx CC--xx))
              Swap  the  point  with the mark.  The current cursor position is
              set to the saved position, and the old cursor position is  saved
              as the mark.
       cchhaarraacctteerr--sseeaarrcchh ((CC--]]))
              A character is read and point is moved to the next occurrence of
              that  character.   A negative argument searches for previous oc-
              currences.
       cchhaarraacctteerr--sseeaarrcchh--bbaacckkwwaarrdd ((MM--CC--]]))
              A character is read and point is moved to  the  previous  occur-
              rence  of that character.  A negative argument searches for sub-
              sequent occurrences.
       sskkiipp--ccssii--sseeqquueennccee
              Read enough characters to consume a multi-key sequence  such  as
              those  defined for keys like Home and End.  Such sequences begin
              with a Control Sequence Indicator (CSI), usually ESC-[.  If this
              sequence is bound to "\[", keys producing  such  sequences  will
              have  no  effect  unless explicitly bound to a readline command,
              instead of inserting stray characters into the  editing  buffer.
              This is unbound by default, but usually bound to ESC-[.
       iinnsseerrtt--ccoommmmeenntt ((MM--##))
              Without  a  numeric  argument,  the  value  of the readline ccoomm--
              mmeenntt--bbeeggiinn variable is inserted at the beginning of the  current
              line.  If a numeric argument is supplied, this command acts as a
              toggle:  if  the  characters at the beginning of the line do not
              match the value of ccoommmmeenntt--bbeeggiinn, the value is inserted,  other-
              wise the characters in ccoommmmeenntt--bbeeggiinn are deleted from the begin-
              ning  of the line.  In either case, the line is accepted as if a
              newline had been typed.   The  default  value  of  ccoommmmeenntt--bbeeggiinn
              causes  this  command  to make the current line a shell comment.
              If a numeric argument causes the comment  character  to  be  re-
              moved, the line will be executed by the shell.
       ssppeellll--ccoorrrreecctt--wwoorrdd ((CC--xx ss))
              Perform  spelling correction on the current word, treating it as
              a directory or filename, in the same way as  the  ccddssppeellll  shell
              option.    Word  boundaries  are  the  same  as  those  used  by
              sshheellll--ffoorrwwaarrdd--wwoorrdd.
       gglloobb--ccoommpplleettee--wwoorrdd ((MM--gg))
              The word before point is treated as a pattern for  pathname  ex-
              pansion,  with an asterisk implicitly appended.  This pattern is
              used to generate a list of matching filenames for possible  com-
              pletions.
       gglloobb--eexxppaanndd--wwoorrdd ((CC--xx **))
              The  word  before point is treated as a pattern for pathname ex-
              pansion, and the list of matching filenames is inserted, replac-
              ing the word.  If a numeric argument is supplied, an asterisk is
              appended before pathname expansion.
       gglloobb--lliisstt--eexxppaannssiioonnss ((CC--xx gg))
              The list  of  expansions  that  would  have  been  generated  by
              gglloobb--eexxppaanndd--wwoorrdd  is  displayed,  and the line is redrawn.  If a
              numeric argument is supplied, an  asterisk  is  appended  before
              pathname expansion.
       dduummpp--ffuunnccttiioonnss
              Print  all  of the functions and their key bindings to the read-
              line output stream.  If a numeric argument is supplied, the out-
              put is formatted in such a way that it can be made  part  of  an
              _i_n_p_u_t_r_c file.
       dduummpp--vvaarriiaabblleess
              Print all of the settable readline variables and their values to
              the  readline output stream.  If a numeric argument is supplied,
              the output is formatted in such a way that it can be  made  part
              of an _i_n_p_u_t_r_c file.
       dduummpp--mmaaccrrooss
              Print  all of the readline key sequences bound to macros and the
              strings they output.  If a numeric  argument  is  supplied,  the
              output is formatted in such a way that it can be made part of an
              _i_n_p_u_t_r_c file.
       ddiissppllaayy--sshheellll--vveerrssiioonn ((CC--xx CC--vv))
              Display version information about the current instance of bbaasshh.

   PPrrooggrraammmmaabbllee CCoommpplleettiioonn
       When  word  completion  is  attempted  for an argument to a command for
       which a completion specification (a _c_o_m_p_s_p_e_c) has  been  defined  using
       the ccoommpplleettee builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below), the programma-
       ble completion facilities are invoked.

       First,  the  command  name  is  identified.  If the command word is the
       empty string (completion attempted at the beginning of an empty  line),
       any  compspec  defined  with  the  --EE option to ccoommpplleettee is used.  If a
       compspec has been defined for that command, the  compspec  is  used  to
       generate the list of possible completions for the word.  If the command
       word  is  a full pathname, a compspec for the full pathname is searched
       for first.  If no compspec is found for the full pathname,  an  attempt
       is  made  to find a compspec for the portion following the final slash.
       If those searches do not result in a  compspec,  any  compspec  defined
       with  the --DD option to ccoommpplleettee is used as the default.  If there is no
       default compspec, bbaasshh attempts alias expansion on the command word  as
       a  final  resort,  and attempts to find a compspec for the command word
       from any successful expansion.

       Once a compspec has been found, it is used  to  generate  the  list  of
       matching  words.   If a compspec is not found, the default bbaasshh comple-
       tion as described above under CCoommpplleettiinngg is performed.

       First, the actions specified by the compspec are  used.   Only  matches
       which  are prefixed by the word being completed are returned.  When the
       --ff or --dd option is used for filename or directory name completion,  the
       shell variable FFIIGGNNOORREE is used to filter the matches.

       Any completions specified by a pathname expansion pattern to the --GG op-
       tion  are  generated next.  The words generated by the pattern need not
       match the word being completed.  The GGLLOOBBIIGGNNOORREE shell variable  is  not
       used to filter the matches, but the FFIIGGNNOORREE variable is used.

       Next,  the string specified as the argument to the --WW option is consid-
       ered.  The string is first split using the characters in the  IIFFSS  spe-
       cial  variable  as delimiters.  Shell quoting is honored.  Each word is
       then expanded using brace expansion,  tilde  expansion,  parameter  and
       variable  expansion, command substitution, and arithmetic expansion, as
       described above under EEXXPPAANNSSIIOONN.  The results are split using the rules
       described above under WWoorrdd SSpplliittttiinngg.  The results of the expansion are
       prefix-matched against the word being completed, and the matching words
       become the possible completions.

       After these matches have been generated, any shell function or  command
       specified  with  the --FF and --CC options is invoked.  When the command or
       function is invoked, the CCOOMMPP__LLIINNEE, CCOOMMPP__PPOOIINNTT, CCOOMMPP__KKEEYY, and CCOOMMPP__TTYYPPEE
       variables are assigned values as described above under SShheellll VVaarriiaabblleess.
       If a shell function is being invoked,  the  CCOOMMPP__WWOORRDDSS  and  CCOOMMPP__CCWWOORRDD
       variables  are  also set.  When the function or command is invoked, the
       first argument ($$11) is the name of the command whose arguments are  be-
       ing  completed,  the  second argument ($$22) is the word being completed,
       and the third argument ($$33) is the word preceding the word  being  com-
       pleted on the current command line.  No filtering of the generated com-
       pletions against the word being completed is performed; the function or
       command has complete freedom in generating the matches.

       Any  function specified with --FF is invoked first.  The function may use
       any of the shell facilities, including the  ccoommppggeenn  builtin  described
       below,  to  generate the matches.  It must put the possible completions
       in the CCOOMMPPRREEPPLLYY array variable, one per array element.

       Next, any command specified with the --CC option is invoked in  an  envi-
       ronment  equivalent to command substitution.  It should print a list of
       completions, one per line, to the standard output.   Backslash  may  be
       used to escape a newline, if necessary.

       After  all of the possible completions are generated, any filter speci-
       fied with the --XX option is applied to the list.  The filter is  a  pat-
       tern  as  used  for  pathname expansion; a && in the pattern is replaced
       with the text of the word being completed.  A literal && may be  escaped
       with  a  backslash; the backslash is removed before attempting a match.
       Any completion that matches the pattern will be removed from the  list.
       A leading !! negates the pattern; in this case any completion not match-
       ing  the  pattern  will be removed.  If the nnooccaasseemmaattcchh shell option is
       enabled, the match is performed without regard to the  case  of  alpha-
       betic characters.

       Finally, any prefix and suffix specified with the --PP and --SS options are
       added to each member of the completion list, and the result is returned
       to the readline completion code as the list of possible completions.

       If  the previously-applied actions do not generate any matches, and the
       --oo ddiirrnnaammeess option was supplied to ccoommpplleettee when the compspec  was  de-
       fined, directory name completion is attempted.

       If  the  --oo  pplluussddiirrss option was supplied to ccoommpplleettee when the compspec
       was defined, directory name completion is attempted and any matches are
       added to the results of the other actions.

       By default, if a compspec is found, whatever it generates  is  returned
       to  the  completion  code as the full set of possible completions.  The
       default bbaasshh completions are not attempted, and the readline default of
       filename completion is disabled.  If the --oo bbaasshhddeeffaauulltt option was sup-
       plied to ccoommpplleettee when the compspec was defined, the bbaasshh default  com-
       pletions are attempted if the compspec generates no matches.  If the --oo
       ddeeffaauulltt  option was supplied to ccoommpplleettee when the compspec was defined,
       readline's default completion will be performed if the  compspec  (and,
       if attempted, the default bbaasshh completions) generate no matches.

       When  a  compspec  indicates that directory name completion is desired,
       the programmable completion functions force readline to append a  slash
       to  completed names which are symbolic links to directories, subject to
       the value of the mmaarrkk--ddiirreeccttoorriieess readline variable, regardless of  the
       setting of the mmaarrkk--ssyymmlliinnkkeedd--ddiirreeccttoorriieess readline variable.

       There  is  some support for dynamically modifying completions.  This is
       most useful when used in combination with a default  completion  speci-
       fied  with  ccoommpplleettee --DD.  It's possible for shell functions executed as
       completion handlers to indicate that completion should  be  retried  by
       returning  an exit status of 124.  If a shell function returns 124, and
       changes the compspec associated with the command on which completion is
       being attempted (supplied as the first argument when  the  function  is
       executed), programmable completion restarts from the beginning, with an
       attempt  to find a new compspec for that command.  This allows a set of
       completions to be built dynamically as completion is attempted,  rather
       than being loaded all at once.

       For  instance, assuming that there is a library of compspecs, each kept
       in a file corresponding to the name of the command, the  following  de-
       fault completion function would load completions dynamically:
              _completion_loader()
              {
                . "/etc/bash_completion.d/$1.sh" \
                  >/dev/null 2>&1 && return 124
              }
              complete -D -F _completion_loader \
                  -o bashdefault -o default

HHIISSTTOORRYY
       When  the  --oo  hhiissttoorryy  option to the sseett builtin is enabled, the shell
       provides access to the _c_o_m_m_a_n_d _h_i_s_t_o_r_y, the list of commands previously
       typed.  The value of the HHIISSTTSSIIZZEE variable is used  as  the  number  of
       commands to save in a history list.  The text of the last HHIISSTTSSIIZZEE com-
       mands  (default  500)  is  saved.  The shell stores each command in the
       history list prior to parameter and variable expansion  (see  EEXXPPAANNSSIIOONN
       above)  but after history expansion is performed, subject to the values
       of the shell variables HHIISSTTIIGGNNOORREE and HHIISSTTCCOONNTTRROOLL.

       On startup, the history is initialized from the file named by the vari-
       able HHIISSTTFFIILLEE (default _~_/_._b_a_s_h___h_i_s_t_o_r_y).  The file named by  the  value
       of  HHIISSTTFFIILLEE  is  truncated,  if necessary, to contain no more than the
       number of lines specified by the value of HHIISSTTFFIILLEESSIIZZEE.   If  HHIISSTTFFIILLEE--
       SSIIZZEE  is unset, or set to null, a non-numeric value, or a numeric value
       less than zero, the history file is not truncated.   When  the  history
       file  is  read, lines beginning with the history comment character fol-
       lowed immediately by a digit are interpreted as timestamps for the fol-
       lowing history line.  These timestamps are optionally displayed depend-
       ing on the value of the HHIISSTTTTIIMMEEFFOORRMMAATT variable.   When  a  shell  with
       history  enabled  exits,  the  last $$HHIISSTTSSIIZZEE lines are copied from the
       history list to $$HHIISSTTFFIILLEE.  If the hhiissttaappppeenndd shell option  is  enabled
       (see  the description of sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below), the
       lines are appended to the history file, otherwise the history  file  is
       overwritten.   If  HHIISSTTFFIILLEE is unset or null, or if the history file is
       unwritable, the history is not saved.  If the  HHIISSTTTTIIMMEEFFOORRMMAATT  variable
       is  set,  time  stamps are written to the history file, marked with the
       history comment character, so they may be preserved across  shell  ses-
       sions.   This  uses  the history comment character to distinguish time-
       stamps from other history lines.  After saving the history, the history
       file is truncated to contain no more than HHIISSTTFFIILLEESSIIZZEE lines.  If HHIISSTT--
       FFIILLEESSIIZZEE is unset, or set to null, a non-numeric value,  or  a  numeric
       value less than zero, the history file is not truncated.

       The  builtin  command ffcc (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) may be used
       to list or edit and re-execute a portion of the history list.  The hhiiss--
       ttoorryy builtin may be used to display or modify the history list and  ma-
       nipulate  the  history  file.   When using command-line editing, search
       commands are available in each editing mode that provide access to  the
       history list.

       The  shell  allows control over which commands are saved on the history
       list.  The HHIISSTTCCOONNTTRROOLL and HHIISSTTIIGGNNOORREE variables are used to  cause  the
       shell to save only a subset of the commands entered.  The ccmmddhhiisstt shell
       option,  if enabled, causes the shell to attempt to save each line of a
       multi-line command in the same history entry, adding  semicolons  where
       necessary  to preserve syntactic correctness.  The lliitthhiisstt shell option
       causes the shell to save the command with embedded newlines instead  of
       semicolons.  See the description of the sshhoopptt builtin below under SSHHEELLLL
       BBUUIILLTTIINN  CCOOMMMMAANNDDSS  for  information  on setting and unsetting shell op-
       tions.

HHIISSTTOORRYY EEXXPPAANNSSIIOONN
       The shell supports a history expansion feature that is similar  to  the
       history  expansion in ccsshh.  This section describes what syntax features
       are available.  This feature is  enabled  by  default  for  interactive
       shells, and can be disabled using the ++HH option to the sseett builtin com-
       mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  Non-interactive shells do not
       perform history expansion by default.

       History expansions introduce words from the history list into the input
       stream,  making  it  easy to repeat commands, insert the arguments to a
       previous command into the current input line, or fix errors in previous
       commands quickly.

       History expansion is performed immediately after  a  complete  line  is
       read,  before  the shell breaks it into words, and is performed on each
       line individually without taking quoting on  previous  lines  into  ac-
       count.   It  takes place in two parts.  The first is to determine which
       line from the history list to use during substitution.  The  second  is
       to  select  portions  of  that line for inclusion into the current one.
       The line selected from the history is the _e_v_e_n_t, and  the  portions  of
       that line that are acted upon are _w_o_r_d_s.  The line is broken into words
       in  the same fashion as when reading input, so that several _m_e_t_a_c_h_a_r_a_c_-
       _t_e_r-separated words surrounded by quotes are considered one word.   The
       _e_v_e_n_t  _d_e_s_i_g_n_a_t_o_r  selects  the event, the optional _w_o_r_d _d_e_s_i_g_n_a_t_o_r se-
       lects words from the event, and various optional _m_o_d_i_f_i_e_r_s  are  avail-
       able to manipulate the selected words.

       History  expansions are introduced by the appearance of the history ex-
       pansion character, which is !! by default.  History expansions  may  ap-
       pear anywhere in the input, but do not nest.

       Only  backslash  (\\)  and single quotes can quote the history expansion
       character, but the history  expansion  character  is  also  treated  as
       quoted if it immediately precedes the closing double quote in a double-
       quoted string.

       Several  characters inhibit history expansion if found immediately fol-
       lowing the history expansion character, even if it is unquoted:  space,
       tab,  newline,  carriage  return, ==, and the other shell metacharacters
       defined above.

       There is a special abbreviation for substitution, active when the _q_u_i_c_k
       _s_u_b_s_t_i_t_u_t_i_o_n character (described above under hhiissttcchhaarrss) is  the  first
       character on the line.  It selects the previous history entry, using an
       event  designator  equivalent to !!!!, and substitutes one string for an-
       other in that line.  It is described  below  under  EEvveenntt  DDeessiiggnnaattoorrss.
       This is the only history expansion that does not begin with the history
       expansion character.

       Several  shell  options  settable with the sshhoopptt builtin may be used to
       tailor the behavior of history expansion.  If the hhiissttvveerriiffyy shell  op-
       tion  is  enabled (see the description of the sshhoopptt builtin below), and
       rreeaaddlliinnee is being  used,  history  substitutions  are  not  immediately
       passed  to  the  shell  parser.  Instead, the expanded line is reloaded
       into the rreeaaddlliinnee editing buffer for further modification.  If rreeaaddlliinnee
       is being used, and the hhiissttrreeeeddiitt shell option  is  enabled,  a  failed
       history  substitution will be reloaded into the rreeaaddlliinnee editing buffer
       for correction.  The --pp option to the hhiissttoorryy builtin  command  may  be
       used  to  see what a history expansion will do before using it.  The --ss
       option to the hhiissttoorryy builtin may be used to add commands to the end of
       the history list without actually executing  them,  so  that  they  are
       available for subsequent recall.

       The  shell allows control of the various characters used by the history
       expansion mechanism (see the description of hhiissttcchhaarrss above under SShheellll
       VVaarriiaabblleess).  The shell uses the history comment character to mark  his-
       tory timestamps when writing the history file.

   EEvveenntt DDeessiiggnnaattoorrss
       An  event designator is a reference to a command line entry in the his-
       tory list.  The event designator consists of the portion  of  the  word
       beginning with the history expansion character and ending with the word
       designator if present, or the end of the word.  Unless the reference is
       absolute,  events  are  relative to the current position in the history
       list.

       !!      Start a history substitution, except when followed by  a  bbllaannkk,
              newline,  carriage return, = or ( (when the eexxttgglloobb shell option
              is enabled using the sshhoopptt builtin).
       !!_n     Refer to command line _n.
       !!--_n    Refer to the current command minus _n.
       !!!!     Refer to the previous command.  This is a synonym for "!-1".
       !!_s_t_r_i_n_g
              Refer to the most recent command preceding the current  position
              in the history list starting with _s_t_r_i_n_g.
       !!??_s_t_r_i_n_g[[??]]
              Refer  to the most recent command preceding the current position
              in the history list containing _s_t_r_i_n_g.  The trailing  ??  may  be
              omitted  if  _s_t_r_i_n_g  is  followed  immediately by a newline.  If
              _s_t_r_i_n_g is missing, the string from the  most  recent  search  is
              used; it is an error if there is no previous search string.
       ^^_s_t_r_i_n_g_1^^_s_t_r_i_n_g_2^^
              Quick  substitution.   Repeat  the  previous  command, replacing
              _s_t_r_i_n_g_1 with  _s_t_r_i_n_g_2.   Equivalent  to  "!!:s^_s_t_r_i_n_g_1^_s_t_r_i_n_g_2^"
              (see MMooddiiffiieerrss below).
       !!##     The entire command line typed so far.

   WWoorrdd DDeessiiggnnaattoorrss
       Word  designators are used to select desired words from the event.  A ::
       separates the event specification from the word designator.  It may  be
       omitted  if  the word designator begins with a ^^, $$, **, --, or %%.  Words
       are numbered from the beginning of the line, with the first word  being
       denoted  by  0  (zero).  Words are inserted into the current line sepa-
       rated by single spaces.

       00 ((zzeerroo))
              The zeroth word.  For the shell, this is the command word.
       _n      The _nth word.
       ^^      The first argument.  That is, word 1.
       $$      The last word.  This is usually the last argument, but will  ex-
              pand to the zeroth word if there is only one word in the line.
       %%      The  first  word matched by the most recent "?_s_t_r_i_n_g?'"  search,
              if the search string begins with a character that is part  of  a
              word.
       _x--_y    A range of words; "-_y" abbreviates "0-_y".
       **      All  of  the words but the zeroth.  This is a synonym for "_1_-_$".
              It is not an error to use ** if there is just  one  word  in  the
              event; the empty string is returned in that case.
       xx**     Abbreviates _x_-_$.
       xx--     Abbreviates _x_-_$ like xx**, but omits the last word.  If xx is miss-
              ing, it defaults to 0.

       If  a  word  designator is supplied without an event specification, the
       previous command is used as the event.

   MMooddiiffiieerrss
       After the optional word designator, there may appear a sequence of  one
       or more of the following modifiers, each preceded by a ":".  These mod-
       ify, or edit, the word or words selected from the history event.

       hh      Remove a trailing filename component, leaving only the head.
       tt      Remove all leading filename components, leaving the tail.
       rr      Remove a trailing suffix of the form _._x_x_x, leaving the basename.
       ee      Remove all but the trailing suffix.
       pp      Print the new command but do not execute it.
       qq      Quote the substituted words, escaping further substitutions.
       xx      Quote  the  substituted words as with qq, but break into words at
              bbllaannkkss and newlines.  The qq and xx modifiers are mutually  exclu-
              sive; the last one supplied is used.
       ss//_o_l_d//_n_e_w//
              Substitute  _n_e_w  for  the  first  occurrence of _o_l_d in the event
              line.  Any character may be used as the delimiter in place of /.
              The final delimiter is optional if it is the last  character  of
              the event line.  The delimiter may be quoted in _o_l_d and _n_e_w with
              a single backslash.  If & appears in _n_e_w, it is replaced by _o_l_d.
              A  single backslash will quote the &.  If _o_l_d is null, it is set
              to the last _o_l_d substituted, or, if no previous history  substi-
              tutions  took  place,  the last _s_t_r_i_n_g in a !!??_s_t_r_i_n_g[[??]]  search.
              If _n_e_w is null, each matching _o_l_d is deleted.
       &&      Repeat the previous substitution.
       gg      Cause changes to be applied over the entire event line.  This is
              used in conjunction with "::ss" (e.g.,  "::ggss//_o_l_d//_n_e_w//")  or  "::&&".
              If  used with "::ss", any delimiter can be used in place of /, and
              the final delimiter is optional if it is the last  character  of
              the event line.  An aa may be used as a synonym for gg.
       GG      Apply the following "ss" or "&&" modifier once to each word in the
              event line.

SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS
       Unless otherwise noted, each builtin command documented in this section
       as accepting options preceded by -- accepts ---- to signify the end of the
       options.  The ::, ttrruuee, ffaallssee, and tteesstt/[[ builtins do not accept options
       and  do  not treat ---- specially.  The eexxiitt, llooggoouutt, rreettuurrnn, bbrreeaakk, ccoonn--
       ttiinnuuee, lleett, and sshhiifftt builtins accept and process  arguments  beginning
       with  -- without requiring ----.  Other builtins that accept arguments but
       are not specified as accepting options  interpret  arguments  beginning
       with  --  as  invalid options and require ---- to prevent this interpreta-
       tion.

       :: [_a_r_g_u_m_e_n_t_s]
              No effect; the command does nothing beyond  expanding  _a_r_g_u_m_e_n_t_s
              and performing any specified redirections.  The return status is
              zero.

       ..  [--pp _p_a_t_h] _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
       ssoouurrccee [--pp _p_a_t_h] _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
              The ..  command (ssoouurrccee) reads and execute commands from _f_i_l_e_n_a_m_e
              in  the current shell environment and returns the exit status of
              the last command executed from _f_i_l_e_n_a_m_e.  If _f_i_l_e_n_a_m_e  does  not
              contain  a  slash,  ..  searchs for it.  If the --pp option is sup-
              plied, ..  treats _p_a_t_h as a colon-separated list  of  directories
              in  which  to  find  _f_i_l_e_n_a_m_e; otherwise, ..  uses the entries in
              PPAATTHH to find the directory containing _f_i_l_e_n_a_m_e.   _f_i_l_e_n_a_m_e  does
              not  need  to be executable.  When bbaasshh is not in _p_o_s_i_x _m_o_d_e, it
              searches the current directory if no file is found in PPAATTHH,  but
              does not search the current directory if --pp is supplied.  If the
              ssoouurrcceeppaatthh  option to the sshhoopptt builtin command is turned off, ..
              does not search PPAATTHH.  If any _a_r_g_u_m_e_n_t_s are supplied,  they  be-
              come  the positional parameters when _f_i_l_e_n_a_m_e is executed.  Oth-
              erwise the positional parameters are unchanged.  If the  --TT  op-
              tion is enabled, .. inherits any trap on DDEEBBUUGG; if it is not, any
              DDEEBBUUGG  trap  string  is saved and restored around the call to ..,
              and .. unsets the DDEEBBUUGG trap while it executes.   If  --TT  is  not
              set,  and the sourced file changes the DDEEBBUUGG trap, the new value
              is retained when .. completes.  The return status is  the  status
              of  the  last command exited within the script (0 if no commands
              are executed), and false if _f_i_l_e_n_a_m_e is not found or  cannot  be
              read.

       aalliiaass [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
              AAlliiaass with no arguments or with the --pp option prints the list of
              aliases  in  the form aalliiaass _n_a_m_e=_v_a_l_u_e on standard output.  When
              arguments are supplied, an alias is defined for each _n_a_m_e  whose
              _v_a_l_u_e  is given.  A trailing space in _v_a_l_u_e causes the next word
              to be checked for alias substitution when the alias is expanded.
              For each _n_a_m_e in the argument list for which no  _v_a_l_u_e  is  sup-
              plied,  the  name  and value of the alias is printed.  AAlliiaass re-
              turns true unless a _n_a_m_e is given for which no  alias  has  been
              defined.

       bbgg [_j_o_b_s_p_e_c ...]
              Resume  each  suspended  job _j_o_b_s_p_e_c in the background, as if it
              had been started with &&.  If _j_o_b_s_p_e_c is not present, the shell's
              notion of the _c_u_r_r_e_n_t _j_o_b is used.  bbgg _j_o_b_s_p_e_c returns 0  unless
              run  when  job control is disabled or, when run with job control
              enabled, any specified _j_o_b_s_p_e_c was  not  found  or  was  started
              without job control.

       bbiinndd [--mm _k_e_y_m_a_p] [--llssvvSSVVXX]
       bbiinndd [--mm _k_e_y_m_a_p] [--qq _f_u_n_c_t_i_o_n] [--uu _f_u_n_c_t_i_o_n] [--rr _k_e_y_s_e_q]
       bbiinndd [--mm _k_e_y_m_a_p] --ff _f_i_l_e_n_a_m_e
       bbiinndd [--mm _k_e_y_m_a_p] --xx _k_e_y_s_e_q[:] _s_h_e_l_l_-_c_o_m_m_a_n_d
       bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_f_u_n_c_t_i_o_n_-_n_a_m_e
       bbiinndd [--mm _k_e_y_m_a_p] --pp|--PP [_r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d]
       bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d
       bbiinndd _r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d_-_l_i_n_e
              Display  current  rreeaaddlliinnee key and function bindings, bind a key
              sequence to a rreeaaddlliinnee function or  macro,  or  set  a  rreeaaddlliinnee
              variable.  Each non-option argument is a command as it would ap-
              pear  in  a  rreeaaddlliinnee  initialization file such as _._i_n_p_u_t_r_c, but
              each binding or command must be passed as a  separate  argument;
              e.g.,  '"\C-x\C-r":  re-read-init-file'.   In  the following de-
              scriptions, output available to be re-read is formatted as  com-
              mands  that  would  appear  in a rreeaaddlliinnee initialization file or
              that would be supplied as individual arguments to  a  bbiinndd  com-
              mand.  Options, if supplied, have the following meanings:
              --mm _k_e_y_m_a_p
                     Use _k_e_y_m_a_p as the keymap to be affected by the subsequent
                     bindings.  Acceptable _k_e_y_m_a_p names are _e_m_a_c_s_, _e_m_a_c_s_-_s_t_a_n_-
                     _d_a_r_d_,  _e_m_a_c_s_-_m_e_t_a_,  _e_m_a_c_s_-_c_t_l_x_,  _v_i_, _v_i_-_m_o_v_e_, _v_i_-_c_o_m_m_a_n_d,
                     and _v_i_-_i_n_s_e_r_t.  _v_i is equivalent to  _v_i_-_c_o_m_m_a_n_d  (_v_i_-_m_o_v_e
                     is  also  a  synonym); _e_m_a_c_s is equivalent to _e_m_a_c_s_-_s_t_a_n_-
                     _d_a_r_d.
              --ll     List the names of all rreeaaddlliinnee functions.
              --pp     Display rreeaaddlliinnee function names and bindings  in  such  a
                     way  that they can be re-read.  If arguments remain after
                     option processing, bbiinndd treats them as  readline  command
                     names and restricts output to those names.
              --PP     List  current  rreeaaddlliinnee  function names and bindings.  If
                     arguments remain after  option  processing,  bbiinndd  treats
                     them  as  readline  command names and restricts output to
                     those names.
              --ss     Display rreeaaddlliinnee key sequences bound to  macros  and  the
                     strings  they  output  in such a way that they can be re-
                     read.
              --SS     Display rreeaaddlliinnee key sequences bound to  macros  and  the
                     strings they output.
              --vv     Display  rreeaaddlliinnee variable names and values in such a way
                     that they can be re-read.
              --VV     List current rreeaaddlliinnee variable names and values.
              --ff _f_i_l_e_n_a_m_e
                     Read key bindings from _f_i_l_e_n_a_m_e.
              --qq _f_u_n_c_t_i_o_n
                     Query about which keys invoke the named _f_u_n_c_t_i_o_n.
              --uu _f_u_n_c_t_i_o_n
                     Unbind all keys bound to the named _f_u_n_c_t_i_o_n.
              --rr _k_e_y_s_e_q
                     Remove any current binding for _k_e_y_s_e_q.
              --xx _k_e_y_s_e_q[[:: ]]_s_h_e_l_l_-_c_o_m_m_a_n_d
                     Cause _s_h_e_l_l_-_c_o_m_m_a_n_d to be executed whenever _k_e_y_s_e_q is en-
                     tered.  The separator between _k_e_y_s_e_q and _s_h_e_l_l_-_c_o_m_m_a_n_d is
                     either whitespace  or  a  colon  optionally  followed  by
                     whitespace.   If  the separator is whitespace, _s_h_e_l_l_-_c_o_m_-
                     _m_a_n_d must be enclosed in double quotes and  rreeaaddlliinnee  ex-
                     pands  any of its special backslash-escapes in _s_h_e_l_l_-_c_o_m_-
                     _m_a_n_d before saving it.  If the separator is a colon,  any
                     enclosing  double  quotes are optional, and rreeaaddlliinnee does
                     not expand the command string before  saving  it.   Since
                     the  entire key binding expression must be a single argu-
                     ment, it should be enclosed in quotes.   When  _s_h_e_l_l_-_c_o_m_-
                     _m_a_n_d  is executed, the shell sets the RREEAADDLLIINNEE__LLIINNEE vari-
                     able to the contents of the rreeaaddlliinnee line buffer and  the
                     RREEAADDLLIINNEE__PPOOIINNTT and RREEAADDLLIINNEE__MMAARRKK variables to the current
                     location  of  the insertion point and the saved insertion
                     point (the mark), respectively.  The  shell  assigns  any
                     numeric  argument the user supplied to the RREEAADDLLIINNEE__AARRGGUU--
                     MMEENNTT variable.  If there was no argument,  that  variable
                     is not set.  If the executed command changes the value of
                     any  of  RREEAADDLLIINNEE__LLIINNEE, RREEAADDLLIINNEE__PPOOIINNTT, or RREEAADDLLIINNEE__MMAARRKK,
                     those new values will be reflected in the editing state.
              --XX     List all key sequences bound to shell  commands  and  the
                     associated commands in a format that can be reused as in-
                     put.

              The  return value is 0 unless an unrecognized option is given or
              an error occurred.

       bbrreeaakk [_n]
              Exit from within a ffoorr, wwhhiillee, uunnttiill, or sseelleecctt loop.  If  _n  is
              specified,  break  _n  levels.   _n must be >= 1.  If _n is greater
              than the number of enclosing loops, all enclosing loops are  ex-
              ited.   The  return  value  is 0 unless _n is not greater than or
              equal to 1.

       bbuuiillttiinn _s_h_e_l_l_-_b_u_i_l_t_i_n [_a_r_g_u_m_e_n_t_s]
              Execute the specified shell builtin, passing it  _a_r_g_u_m_e_n_t_s,  and
              return its exit status.  This is useful when defining a function
              whose  name  is the same as a shell builtin, retaining the func-
              tionality of the builtin within the function.  The ccdd builtin is
              commonly redefined this way.  The  return  status  is  false  if
              _s_h_e_l_l_-_b_u_i_l_t_i_n is not a shell builtin command.

       ccaalllleerr [_e_x_p_r]
              Returns the context of any active subroutine call (a shell func-
              tion or a script executed with the .. or ssoouurrccee builtins).  With-
              out _e_x_p_r, ccaalllleerr displays the line number and source filename of
              the  current subroutine call.  If a non-negative integer is sup-
              plied as _e_x_p_r, ccaalllleerr displays the line number, subroutine name,
              and source file corresponding to that position  in  the  current
              execution  call  stack.  This extra information may be used, for
              example, to print a stack trace.  The current frame is frame  0.
              The  return  value is 0 unless the shell is not executing a sub-
              routine call or _e_x_p_r does not correspond to a valid position  in
              the call stack.

       ccdd [--LL|[--PP [--ee]]] [-@] [_d_i_r]
              Change  the  current  directory to _d_i_r.  if _d_i_r is not supplied,
              the value of the HHOOMMEE shell variable is the default.  The  vari-
              able CCDDPPAATTHH defines the search path for the directory containing
              _d_i_r:  the  shell searches each directory name in CCDDPPAATTHH for _d_i_r.
              Alternative directory names in CCDDPPAATTHH are separated by  a  colon
              (:).  A null directory name in CCDDPPAATTHH is the same as the current
              directory,  i.e., ".".  If _d_i_r begins with a slash (/), then CCDD--
              PPAATTHH is not used.  The --PP option causes ccdd to use  the  physical
              directory structure by resolving symbolic links while traversing
              _d_i_r  and  before processing instances of _._. in _d_i_r (see also the
              --PP option to the sseett builtin command); the --LL option forces sym-
              bolic links to be followed by resolving the link after  process-
              ing  instances  of  _._.  in  _d_i_r.   If  _._.  appears in _d_i_r, it is
              processed by removing the immediately previous  pathname  compo-
              nent  from _d_i_r, back to a slash or the beginning of _d_i_r.  If the
              --ee option is supplied with --PP, and the current working directory
              cannot be successfully determined after a  successful  directory
              change,  ccdd will return an unsuccessful status.  On systems that
              support it, the --@@ option presents the extended attributes asso-
              ciated with a file as a directory.  An argument  of  --  is  con-
              verted  to $$OOLLDDPPWWDD before the directory change is attempted.  If
              a non-empty directory name from CCDDPPAATTHH is used, or if --  is  the
              first  argument, and the directory change is successful, the ab-
              solute pathname of the new working directory is written  to  the
              standard output.  If the directory change is successful, ccdd sets
              the  value  of the PPWWDD environment variable to the new directory
              name, and sets the OOLLDDPPWWDD environment variable to the  value  of
              the  current  working  directory  before the change.  The return
              value is true if the directory was successfully  changed;  false
              otherwise.

       ccoommmmaanndd [--ppVVvv] _c_o_m_m_a_n_d [_a_r_g ...]
              Run  _c_o_m_m_a_n_d  with  _a_r_g_s  suppressing  the normal shell function
              lookup.  Only builtin commands or commands found in the PPAATTHH are
              executed.  If the --pp option is given, the search for _c_o_m_m_a_n_d  is
              performed  using  a default value for PPAATTHH that is guaranteed to
              find all of the standard utilities.  If either the --VV or --vv  op-
              tion  is  supplied, a description of _c_o_m_m_a_n_d is printed.  The --vv
              option causes a single word indicating the command  or  filename
              used to invoke _c_o_m_m_a_n_d to be displayed; the --VV option produces a
              more  verbose  description.  If the --VV or --vv option is supplied,
              the exit status is 0 if _c_o_m_m_a_n_d was found, and  1  if  not.   If
              neither option is supplied and an error occurred or _c_o_m_m_a_n_d can-
              not  be found, the exit status is 127.  Otherwise, the exit sta-
              tus of the ccoommmmaanndd builtin is the exit status of _c_o_m_m_a_n_d.

       ccoommppggeenn [--VV _v_a_r_n_a_m_e] [_o_p_t_i_o_n] [_w_o_r_d]
              Generate possible completion matches for _w_o_r_d according  to  the
              _o_p_t_i_o_ns,  which  may  be  any  option  accepted  by the ccoommpplleettee
              builtin with the exceptions of --pp, --rr, --DD, --EE, and --II, and write
              the matches to the standard output.  If the --VV  option  is  sup-
              plied, ccoommppggeenn stores the generated completions into the indexed
              array  variable  _v_a_r_n_a_m_e instead of writing them to the standard
              output.  When using the --FF or  --CC  options,  the  various  shell
              variables  set  by the programmable completion facilities, while
              available, will not have useful values.

              The matches will be generated in the same way as if the program-
              mable completion code had generated them directly from a comple-
              tion specification with the same flags.  If _w_o_r_d  is  specified,
              only those completions matching _w_o_r_d will be displayed.

              The  return  value is true unless an invalid option is supplied,
              or no matches were generated.

       ccoommpplleettee [--aabbccddeeffggjjkkssuuvv] [--oo _c_o_m_p_-_o_p_t_i_o_n] [--DDEEII] [--AA _a_c_t_i_o_n]
              [--GG _g_l_o_b_p_a_t] [--WW _w_o_r_d_l_i_s_t] [--FF _f_u_n_c_t_i_o_n] [--CC _c_o_m_m_a_n_d]
              [--XX _f_i_l_t_e_r_p_a_t] [--PP _p_r_e_f_i_x] [--SS _s_u_f_f_i_x] _n_a_m_e [_n_a_m_e ...]
       ccoommpplleettee --pprr [--DDEEII] [_n_a_m_e ...]
              Specify how arguments to each _n_a_m_e should be completed.  If  the
              --pp  option  is supplied, or if no options or _n_a_m_es are supplied,
              existing completion specifications are printed in a way that al-
              lows them to be reused as input.  The --rr option removes  a  com-
              pletion  specification  for  each _n_a_m_e, or, if no _n_a_m_es are sup-
              plied, all completion specifications.  The --DD  option  indicates
              that other supplied options and actions should apply to the "de-
              fault"  command  completion;  that is, completion attempted on a
              command for which no completion  has  previously  been  defined.
              The  --EE option indicates that other supplied options and actions
              should apply to "empty" command completion; that is,  completion
              attempted  on  a blank line.  The --II option indicates that other
              supplied options and actions should apply to completion  on  the
              initial  non-assignment word on the line, or after a command de-
              limiter such as ;; or ||, which is usually  command  name  comple-
              tion.   If  multiple  options  are supplied, the --DD option takes
              precedence over --EE, and both take precedence over --II.  If any of
              --DD, --EE, or --II are supplied, any other  _n_a_m_e  arguments  are  ig-
              nored; these completions only apply to the case specified by the
              option.

              The  process  of  applying  these completion specifications when
              word completion is attempted is described above under PPrrooggrraammmmaa--
              bbllee CCoommpplleettiioonn.

              Other options, if specified, have the following  meanings.   The
              arguments  to the --GG, --WW, and --XX options (and, if necessary, the
              --PP and --SS options) should be quoted to protect them from  expan-
              sion before the ccoommpplleettee builtin is invoked.

              --oo _c_o_m_p_-_o_p_t_i_o_n
                      The  _c_o_m_p_-_o_p_t_i_o_n  controls  several aspects of the comp-
                      spec's behavior beyond the simple generation of  comple-
                      tions.  _c_o_m_p_-_o_p_t_i_o_n may be one of:
                      bbaasshhddeeffaauulltt
                              Perform the rest of the default bbaasshh completions
                              if the compspec generates no matches.
                      ddeeffaauulltt Use  readline's  default  filename completion if
                              the compspec generates no matches.
                      ddiirrnnaammeess
                              Perform directory name completion if  the  comp-
                              spec generates no matches.
                      ffiilleennaammeess
                              Tell  readline that the compspec generates file-
                              names, so it can perform  any  filename-specific
                              processing  (like  adding  a  slash to directory
                              names, quoting special characters, or  suppress-
                              ing  trailing spaces).  Intended to be used with
                              shell functions.
                      ffuullllqquuoottee
                              Tell readline to quote all the  completed  words
                              even if they are not filenames.
                      nnooqquuoottee Tell  readline  not to quote the completed words
                              if they are filenames (quoting filenames is  the
                              default).
                      nnoossoorrtt  Tell  readline  not to sort the list of possible
                              completions alphabetically.
                      nnoossppaaccee Tell readline not to append  a  space  (the  de-
                              fault)  to  words  completed  at  the end of the
                              line.
                      pplluussddiirrss
                              After any matches defined by  the  compspec  are
                              generated,  directory  name  completion  is  at-
                              tempted and any matches are added to the results
                              of the other actions.
              --AA _a_c_t_i_o_n
                      The _a_c_t_i_o_n may be one of the  following  to  generate  a
                      list of possible completions:
                      aalliiaass   Alias names.  May also be specified as --aa.
                      aarrrraayyvvaarr
                              Array variable names.
                      bbiinnddiinngg RReeaaddlliinnee key binding names.
                      bbuuiillttiinn Names  of  shell  builtin commands.  May also be
                              specified as --bb.
                      ccoommmmaanndd Command names.  May also be specified as --cc.
                      ddiirreeccttoorryy
                              Directory names.  May also be specified as --dd.
                      ddiissaabblleedd
                              Names of disabled shell builtins.
                      eennaabblleedd Names of enabled shell builtins.
                      eexxppoorrtt  Names of exported shell variables.  May also  be
                              specified as --ee.
                      ffiillee    File names.  May also be specified as --ff.
                      ffuunnccttiioonn
                              Names of shell functions.
                      ggrroouupp   Group names.  May also be specified as --gg.
                      hheellppttooppiicc
                              Help topics as accepted by the hheellpp builtin.
                      hhoossttnnaammee
                              Hostnames,  as  taken from the file specified by
                              the HHOOSSTTFFIILLEE shell variable.
                      jjoobb     Job names, if job control is active.   May  also
                              be specified as --jj.
                      kkeeyywwoorrdd Shell  reserved words.  May also be specified as
                              --kk.
                      rruunnnniinngg Names of running jobs, if job control is active.
                      sseerrvviiccee Service names.  May also be specified as --ss.
                      sseettoopptt  Valid arguments for the --oo  option  to  the  sseett
                              builtin.
                      sshhoopptt   Shell  option  names  as  accepted  by the sshhoopptt
                              builtin.
                      ssiiggnnaall  Signal names.
                      ssttooppppeedd Names of stopped jobs, if job control is active.
                      uusseerr    User names.  May also be specified as --uu.
                      vvaarriiaabbllee
                              Names of all shell variables.  May also be spec-
                              ified as --vv.
              --CC _c_o_m_m_a_n_d
                      _c_o_m_m_a_n_d is executed in a subshell environment,  and  its
                      output  is  used as the possible completions.  Arguments
                      are passed as with the --FF option.
              --FF _f_u_n_c_t_i_o_n
                      The shell function _f_u_n_c_t_i_o_n is executed in  the  current
                      shell  environment.   When the function is executed, the
                      first argument ($$11) is the name of the command whose ar-
                      guments are being completed, the second argument ($$22) is
                      the word being completed, and the third argument ($$33) is
                      the word preceding the word being completed on the  cur-
                      rent  command line.  When it finishes, the possible com-
                      pletions are retrieved from the value of  the  CCOOMMPPRREEPPLLYY
                      array variable.
              --GG _g_l_o_b_p_a_t
                      The  pathname  expansion  pattern _g_l_o_b_p_a_t is expanded to
                      generate the possible completions.
              --PP _p_r_e_f_i_x
                      _p_r_e_f_i_x is added at the beginning of each  possible  com-
                      pletion after all other options have been applied.
              --SS _s_u_f_f_i_x
                      _s_u_f_f_i_x is appended to each possible completion after all
                      other options have been applied.
              --WW _w_o_r_d_l_i_s_t
                      The  _w_o_r_d_l_i_s_t  is  split using the characters in the IIFFSS
                      special variable as delimiters, and each resultant  word
                      is  expanded.  Shell quoting is honored within _w_o_r_d_l_i_s_t,
                      in order to provide a mechanism for the words to contain
                      shell metacharacters or characters in the value of  IIFFSS.
                      The  possible  completions are the members of the resul-
                      tant list which match the word being completed.
              --XX _f_i_l_t_e_r_p_a_t
                      _f_i_l_t_e_r_p_a_t is a pattern as used for  pathname  expansion.
                      It is applied to the list of possible completions gener-
                      ated  by  the  preceding options and arguments, and each
                      completion matching _f_i_l_t_e_r_p_a_t is removed from the  list.
                      A  leading  !!  in _f_i_l_t_e_r_p_a_t negates the pattern; in this
                      case, any completion not matching _f_i_l_t_e_r_p_a_t is removed.

              The return value is true unless an invalid option  is  supplied,
              an option other than --pp, --rr, --DD, --EE, or --II is supplied without a
              _n_a_m_e  argument, an attempt is made to remove a completion speci-
              fication for a _n_a_m_e for which no specification exists, or an er-
              ror occurs adding a completion specification.

       ccoommppoopptt [--oo _o_p_t_i_o_n] [--DDEEII] [++oo _o_p_t_i_o_n] [_n_a_m_e]
              Modify completion options for each _n_a_m_e  according  to  the  _o_p_-
              _t_i_o_ns, or for the currently-executing completion if no _n_a_m_es are
              supplied.   If  no _o_p_t_i_o_ns are given, display the completion op-
              tions for each _n_a_m_e or the  current  completion.   The  possible
              values  of  _o_p_t_i_o_n  are those valid for the ccoommpplleettee builtin de-
              scribed above.  The --DD option indicates that other supplied  op-
              tions should apply to the "default" command completion; that is,
              completion  attempted  on  a command for which no completion has
              previously been defined.  The --EE  option  indicates  that  other
              supplied  options  should  apply  to "empty" command completion;
              that is, completion attempted on a blank line.   The  --II  option
              indicates that other supplied options should apply to completion
              on  the initial non-assignment word on the line, or after a com-
              mand delimiter such as ;; or ||, which  is  usually  command  name
              completion.

              The  return  value is true unless an invalid option is supplied,
              an attempt is made to modify the options for a _n_a_m_e for which no
              completion specification exists, or an output error occurs.

       ccoonnttiinnuuee [_n]
              Resume the next iteration of the enclosing ffoorr, wwhhiillee, uunnttiill, or
              sseelleecctt loop.  If _n is specified, resume  at  the  _nth  enclosing
              loop.   _n  must be >= 1.  If _n is greater than the number of en-
              closing loops, the shell resumes the last  enclosing  loop  (the
              "top-level"  loop).   The  return  value  is  0  unless _n is not
              greater than or equal to 1.

       ddeeccllaarree [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
       ttyyppeesseett [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
              Declare variables and/or give them attributes.  If no _n_a_m_es  are
              given  then display the values of variables.  The --pp option will
              display the attributes and values of each _n_a_m_e.  When --pp is used
              with _n_a_m_e arguments, additional options, other than --ff  and  --FF,
              are  ignored.   When  --pp  is supplied without _n_a_m_e arguments, it
              will display the attributes and values of all  variables  having
              the attributes specified by the additional options.  If no other
              options  are  supplied with --pp, ddeeccllaarree will display the attrib-
              utes and values of all shell variables.  The --ff option will  re-
              strict  the  display to shell functions.  The --FF option inhibits
              the display of function definitions; only the function name  and
              attributes are printed.  If the eexxttddeebbuugg shell option is enabled
              using  sshhoopptt,  the  source  file name and line number where each
              _n_a_m_e is defined are displayed as well.  The  --FF  option  implies
              --ff.  The --gg option forces variables to be created or modified at
              the global scope, even when ddeeccllaarree is executed in a shell func-
              tion.   It  is ignored in all other cases.  The --II option causes
              local variables to inherit the attributes  (except  the  _n_a_m_e_r_e_f
              attribute) and value of any existing variable with the same _n_a_m_e
              at  a  surrounding scope.  If there is no existing variable, the
              local variable is initially unset.  The following options can be
              used to restrict output to  variables  with  the  specified  at-
              tribute or to give variables attributes:
              --aa     Each  _n_a_m_e  is  an  indexed  array  variable  (see AArrrraayyss
                     above).
              --AA     Each _n_a_m_e is an associative array  variable  (see  AArrrraayyss
                     above).
              --ff     Use function names only.
              --ii     The variable is treated as an integer; arithmetic evalua-
                     tion  (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN above) is performed when
                     the variable is assigned a value.
              --ll     When the variable is assigned  a  value,  all  upper-case
                     characters  are  converted to lower-case.  The upper-case
                     attribute is disabled.
              --nn     Give each _n_a_m_e the _n_a_m_e_r_e_f attribute, making  it  a  name
                     reference  to  another  variable.  That other variable is
                     defined by the value of _n_a_m_e.   All  references,  assign-
                     ments,  and attribute modifications to _n_a_m_e, except those
                     using or changing the --nn attribute itself, are  performed
                     on  the variable referenced by _n_a_m_e's value.  The nameref
                     attribute cannot be applied to array variables.
              --rr     Make _n_a_m_es readonly.  These names cannot then be assigned
                     values by subsequent assignment statements or unset.
              --tt     Give each _n_a_m_e the _t_r_a_c_e attribute.  Traced functions in-
                     herit the DDEEBBUUGG and RREETTUURRNN traps from the calling  shell.
                     The trace attribute has no special meaning for variables.
              --uu     When  the  variable  is  assigned a value, all lower-case
                     characters are converted to upper-case.   The  lower-case
                     attribute is disabled.
              --xx     Mark  _n_a_m_es for export to subsequent commands via the en-
                     vironment.

              Using "+" instead of "-" turns off the attribute  instead,  with
              the  exceptions  that ++aa and ++AA may not be used to destroy array
              variables and ++rr will not remove the readonly  attribute.   When
              used in a function, ddeeccllaarree and ttyyppeesseett make each _n_a_m_e local, as
              with  the llooccaall command, unless the --gg option is supplied.  If a
              variable name is followed by =_v_a_l_u_e, the value of  the  variable
              is  set  to _v_a_l_u_e.  When using --aa or --AA and the compound assign-
              ment syntax to create array variables, additional attributes  do
              not  take effect until subsequent assignments.  The return value
              is 0 unless an invalid option is encountered, an attempt is made
              to define a function using "-f foo=bar".  an attempt is made  to
              assign a value to a readonly variable, an attempt is made to as-
              sign a value to an array variable without using the compound as-
              signment  syntax  (see  AArrrraayyss above), one of the _n_a_m_e_s is not a
              valid shell variable name, an attempt is made to turn off  read-
              only  status for a readonly variable, an attempt is made to turn
              off array status for an array variable, or an attempt is made to
              display a non-existent function with --ff.

       ddiirrss [[--ccllppvv]] [[++_n]] [[--_n]]
              Without options, displays the list of currently  remembered  di-
              rectories.   The default display is on a single line with direc-
              tory names separated by spaces.  Directories are  added  to  the
              list  with  the  ppuusshhdd command; the ppooppdd command removes entries
              from the list.  The current directory is always the first direc-
              tory in the stack.
              --cc     Clears the directory stack by deleting  all  of  the  en-
                     tries.
              --ll     Produces  a  listing  using  full  pathnames; the default
                     listing format uses a tilde to denote the home directory.
              --pp     Print the directory stack with one entry per line.
              --vv     Print the directory stack with one entry per  line,  pre-
                     fixing each entry with its index in the stack.
              ++_n     Displays the _nth entry counting from the left of the list
                     shown by ddiirrss when invoked without options, starting with
                     zero.
              --_n     Displays  the  _nth  entry  counting from the right of the
                     list shown by ddiirrss when invoked without options, starting
                     with zero.

              The return value is 0 unless an invalid option is supplied or  _n
              indexes beyond the end of the directory stack.

       ddiissoowwnn [--aarr] [--hh] [_j_o_b_s_p_e_c ... | _p_i_d ... ]
              Without  options,  remove  each _j_o_b_s_p_e_c from the table of active
              jobs.  If _j_o_b_s_p_e_c is not present, and neither the --aa nor the  --rr
              option  is  supplied, the _c_u_r_r_e_n_t _j_o_b is used.  If the --hh option
              is given, each _j_o_b_s_p_e_c is not removed from  the  table,  but  is
              marked  so  that  SSIIGGHHUUPP is not sent to the job if the shell re-
              ceives a SSIIGGHHUUPP.  If no _j_o_b_s_p_e_c is supplied, the --aa option means
              to remove or mark all jobs; the --rr option without a _j_o_b_s_p_e_c  ar-
              gument restricts operation to running jobs.  The return value is
              0 unless a _j_o_b_s_p_e_c does not specify a valid job.

       eecchhoo [--nneeEE] [_a_r_g ...]
              Output  the  _a_r_gs,  separated  by spaces, followed by a newline.
              The return status is 0 unless a write error occurs.   If  --nn  is
              specified, the trailing newline is suppressed.  If the --ee option
              is  given,  interpretation  of  the  following backslash-escaped
              characters is enabled.  The --EE option disables  the  interpreta-
              tion  of these escape characters, even on systems where they are
              interpreted by default.  The xxppgg__eecchhoo shell option may  be  used
              to  dynamically determine whether or not eecchhoo interprets any op-
              tions and expands these escape characters by default.  eecchhoo does
              not interpret ---- to mean the end of  options.   eecchhoo  interprets
              the following escape sequences:
              \\aa     alert (bell)
              \\bb     backspace
              \\cc     suppress further output
              \\ee
              \\EE     an escape character
              \\ff     form feed
              \\nn     new line
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\\\     backslash
              \\00_n_n_n  the  eight-bit  character  whose value is the octal value
                     _n_n_n (zero to three octal digits)
              \\xx_H_H   the eight-bit character whose value  is  the  hexadecimal
                     value _H_H (one or two hex digits)
              \\uu_H_H_H_H the  Unicode (ISO/IEC 10646) character whose value is the
                     hexadecimal value _H_H_H_H (one to four hex digits)
              \\UU_H_H_H_H_H_H_H_H
                     the Unicode (ISO/IEC 10646) character whose value is  the
                     hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits)

       eennaabbllee [--aa] [--ddnnppss] [--ff _f_i_l_e_n_a_m_e] [_n_a_m_e ...]
              Enable  and disable builtin shell commands.  Disabling a builtin
              allows a disk command which has the same name as a shell builtin
              to be executed without specifying a full pathname,  even  though
              the  shell  normally searches for builtins before disk commands.
              If --nn is used, each _n_a_m_e is disabled; otherwise, _n_a_m_e_s  are  en-
              abled.   For  example, to use the tteesstt binary found via the PPAATTHH
              instead of the shell builtin version, run "enable -n test".  The
              --ff option means to load the new builtin command _n_a_m_e from shared
              object _f_i_l_e_n_a_m_e, on systems that support dynamic loading.   BBaasshh
              will  use  the  value  of  the BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH variable as a
              colon-separated list of directories in which to search for _f_i_l_e_-
              _n_a_m_e, if _f_i_l_e_n_a_m_e does not contain a slash.  The default is sys-
              tem-dependent, and may include "." to force a search of the cur-
              rent directory.  The --dd option will delete a builtin  previously
              loaded  with  --ff.   If no _n_a_m_e arguments are given, or if the --pp
              option is supplied, a list of shell builtins is  printed.   With
              no  other  option  arguments,  the  list consists of all enabled
              shell builtins.  If --nn is supplied, only disabled  builtins  are
              printed.   If  --aa  is  supplied,  the  list printed includes all
              builtins, with an indication of whether or not each is  enabled.
              If --ss is supplied, the output is restricted to the POSIX _s_p_e_c_i_a_l
              builtins.   If no options are supplied and a _n_a_m_e is not a shell
              builtin, eennaabbllee will attempt to load _n_a_m_e from a  shared  object
              named  _n_a_m_e,  as if the command were "enable -f _n_a_m_e _n_a_m_e".  The
              return value is 0 unless a _n_a_m_e is not a shell builtin or  there
              is an error loading a new builtin from a shared object.

       eevvaall [_a_r_g ...]
              The  _a_r_gs  are read and concatenated together into a single com-
              mand.  This command is then read and executed by the shell,  and
              its  exit status is returned as the value of eevvaall.  If there are
              no _a_r_g_s, or only null arguments, eevvaall returns 0.

       eexxeecc [--ccll] [--aa _n_a_m_e] [_c_o_m_m_a_n_d [_a_r_g_u_m_e_n_t_s]]
              If _c_o_m_m_a_n_d is specified, it replaces the shell.  No new  process
              is  created.  The _a_r_g_u_m_e_n_t_s become the arguments to _c_o_m_m_a_n_d.  If
              the --ll option is supplied, the shell places a dash at the begin-
              ning of the zeroth argument passed to _c_o_m_m_a_n_d.  This is what _l_o_-
              _g_i_n(1) does.  The --cc option causes _c_o_m_m_a_n_d to be  executed  with
              an  empty environment.  If --aa is supplied, the shell passes _n_a_m_e
              as the zeroth argument to the executed command.  If _c_o_m_m_a_n_d can-
              not be executed for some reason, a non-interactive shell  exits,
              unless  the  eexxeeccffaaiill shell option is enabled.  In that case, it
              returns failure.  An interactive shell returns  failure  if  the
              file  cannot  be  executed.  A subshell exits unconditionally if
              eexxeecc fails.  If _c_o_m_m_a_n_d is not specified, any redirections  take
              effect  in  the  current  shell, and the return status is 0.  If
              there is a redirection error, the return status is 1.

       eexxiitt [_n]
              Cause the shell to exit with a status of _n.  If  _n  is  omitted,
              the exit status is that of the last command executed.  A trap on
              EEXXIITT is executed before the shell terminates.

       eexxppoorrtt [--ffnn] [_n_a_m_e[=_w_o_r_d]] ...
       eexxppoorrtt --pp
              The  supplied _n_a_m_e_s are marked for automatic export to the envi-
              ronment of subsequently executed commands.  If the --ff option  is
              given,  the _n_a_m_e_s refer to functions.  If no _n_a_m_e_s are given, or
              if the --pp option is supplied, a list of names  of  all  exported
              variables  is printed.  The --nn option causes the export property
              to be removed from each _n_a_m_e.  If a variable name is followed by
              =_w_o_r_d, the value of the variable is set to _w_o_r_d.  eexxppoorrtt returns
              an exit status of 0 unless an invalid option is encountered, one
              of the _n_a_m_e_s is not a valid shell variable name, or --ff  is  sup-
              plied with a _n_a_m_e that is not a function.

       ffaallssee  Does nothing, returns a non-zero status.

       ffcc [--ee _e_n_a_m_e] [--llnnrr] [_f_i_r_s_t] [_l_a_s_t]
       ffcc --ss [_p_a_t=_r_e_p] [_c_m_d]
              The  first  form  selects a range of commands from _f_i_r_s_t to _l_a_s_t
              from the history list and  displays  or  edits  and  re-executes
              them.   _F_i_r_s_t  and  _l_a_s_t may be specified as a string (to locate
              the last command beginning with that string) or as a number  (an
              index  into the history list, where a negative number is used as
              an offset from the current command  number).   When  listing,  a
              _f_i_r_s_t  or  _l_a_s_t of 0 is equivalent to -1 and -0 is equivalent to
              the current command (usually the ffcc  command);  otherwise  0  is
              equivalent  to  -1 and -0 is invalid.  If _l_a_s_t is not specified,
              it is set to the current command for listing  (so  that  "fc  -l
              -10"  prints  the  last 10 commands) and to _f_i_r_s_t otherwise.  If
              _f_i_r_s_t is not specified, it is set to the  previous  command  for
              editing and -16 for listing.

              The  --nn option suppresses the command numbers when listing.  The
              --rr option reverses the order of the commands.  If the --ll  option
              is  given,  the  commands are listed on standard output.  Other-
              wise, the editor given by _e_n_a_m_e is invoked on a file  containing
              those  commands.  If _e_n_a_m_e is not given, the value of the FFCCEEDDIITT
              variable is used, and the value of EEDDIITTOORR if FFCCEEDDIITT is not  set.
              If  neither  variable  is set, _v_i is used.  When editing is com-
              plete, the edited commands are echoed and executed.

              In the second form, _c_o_m_m_a_n_d is re-executed after  each  instance
              of  _p_a_t  is replaced by _r_e_p.  _C_o_m_m_a_n_d is interpreted the same as
              _f_i_r_s_t above.  A useful alias to use with this is "r="fc -s"", so
              that typing "r cc" runs the last command beginning with "cc" and
              typing "r" re-executes the last command.

              If the first form is used, the return value is 0 unless  an  in-
              valid  option  is  encountered  or _f_i_r_s_t or _l_a_s_t specify history
              lines out of range.  If the --ee option is  supplied,  the  return
              value is the value of the last command executed or failure if an
              error occurs with the temporary file of commands.  If the second
              form  is  used, the return status is that of the command re-exe-
              cuted, unless _c_m_d does not specify  a  valid  history  line,  in
              which case ffcc returns failure.

       ffgg [_j_o_b_s_p_e_c]
              Resume  _j_o_b_s_p_e_c  in the foreground, and make it the current job.
              If _j_o_b_s_p_e_c is not present, the shell's notion of the _c_u_r_r_e_n_t _j_o_b
              is used.  The return value is that of the  command  placed  into
              the  foreground,  or failure if run when job control is disabled
              or, when run with job control enabled, if _j_o_b_s_p_e_c does not spec-
              ify a valid job or _j_o_b_s_p_e_c specifies  a  job  that  was  started
              without job control.

       ggeettooppttss _o_p_t_s_t_r_i_n_g _n_a_m_e [_a_r_g ...]
              ggeettooppttss  is used by shell procedures to parse positional parame-
              ters.  _o_p_t_s_t_r_i_n_g contains the option  characters  to  be  recog-
              nized;  if a character is followed by a colon, the option is ex-
              pected to have an argument, which should be separated from it by
              white space.  The colon and question mark characters may not  be
              used  as  option  characters.   Each time it is invoked, ggeettooppttss
              places the next option in the shell variable _n_a_m_e,  initializing
              _n_a_m_e if it does not exist, and the index of the next argument to
              be processed into the variable OOPPTTIINNDD.  OOPPTTIINNDD is initialized to
              1 each time the shell or a shell script is invoked.  When an op-
              tion requires an argument, ggeettooppttss places that argument into the
              variable OOPPTTAARRGG.  The shell does not reset OOPPTTIINNDD automatically;
              it  must  be  manually  reset  between multiple calls to ggeettooppttss
              within the same shell invocation if a new set of  parameters  is
              to be used.

              When the end of options is encountered, ggeettooppttss exits with a re-
              turn value greater than zero.  OOPPTTIINNDD is set to the index of the
              first non-option argument, and _n_a_m_e is set to ?.

              ggeettooppttss  normally  parses the positional parameters, but if more
              arguments are supplied as _a_r_g values, ggeettooppttss parses  those  in-
              stead.

              ggeettooppttss  can  report errors in two ways.  If the first character
              of _o_p_t_s_t_r_i_n_g is a colon, _s_i_l_e_n_t error  reporting  is  used.   In
              normal  operation,  diagnostic messages are printed when invalid
              options or missing option arguments  are  encountered.   If  the
              variable  OOPPTTEERRRR  is  set  to  0, no error messages will be dis-
              played, even if the first character of _o_p_t_s_t_r_i_n_g is not a colon.

              If ggeettooppttss detects an invalid option, it places ? into _n_a_m_e and,
              if not silent, prints an error message and  unsets  OOPPTTAARRGG.   If
              ggeettooppttss  is silent, it assigns the option character found to OOPP--
              TTAARRGG and does not print a diagnostic message.

              If a required argument is not found, and ggeettooppttss is not  silent,
              it sets the value of _n_a_m_e to a question mark (??), unsets OOPPTTAARRGG,
              and  prints a diagnostic message.  If ggeettooppttss is silent, it sets
              the value of _n_a_m_e to a colon (::) and sets OOPPTTAARRGG to  the  option
              character found.

              ggeettooppttss  returns true if an option, specified or unspecified, is
              found.  It returns false if the end of options is encountered or
              an error occurs.

       hhaasshh [--llrr] [--pp _f_i_l_e_n_a_m_e] [--ddtt] [_n_a_m_e]
              Each time hhaasshh is invoked, the full pathname of the command _n_a_m_e
              is determined by searching the directories in $$PPAATTHH  and  remem-
              bered.  Any previously-remembered pathname is discarded.  If the
              --pp  option  is supplied, hhaasshh uses _f_i_l_e_n_a_m_e as the full filename
              of the command.  The --rr option causes the shell  to  forget  all
              remembered  locations.   Assigning  to  the  PPAATTHH  variable also
              clears all hashed filenames.  The --dd option causes the shell  to
              forget  the  remembered location of each _n_a_m_e.  If the --tt option
              is supplied, the full pathname to which each _n_a_m_e corresponds is
              printed.  If multiple _n_a_m_e arguments are supplied with  --tt,  the
              _n_a_m_e  is printed before the hashed full pathname.  The --ll option
              causes output to be displayed in a format that may be reused  as
              input.   If  no  arguments are given, or if only --ll is supplied,
              information about remembered commands is printed.  The  --tt,  --dd,
              and  --pp options (the options that act on the _n_a_m_e arguments) are
              mutually exclusive.  Only one will be active.  If more than  one
              is supplied, --tt has higher priority than --pp, and both are higher
              priority  than  --dd.   The return status is true unless a _n_a_m_e is
              not found or an invalid option is supplied.

       hheellpp [--ddmmss] [_p_a_t_t_e_r_n]
              Display helpful information about builtin commands.  If  _p_a_t_t_e_r_n
              is  specified, hheellpp gives detailed help on all commands matching
              _p_a_t_t_e_r_n; otherwise help for all the builtins and  shell  control
              structures is printed.
              --dd     Display a short description of each _p_a_t_t_e_r_n
              --mm     Display the description of each _p_a_t_t_e_r_n in a manpage-like
                     format
              --ss     Display only a short usage synopsis for each _p_a_t_t_e_r_n

              The return status is 0 unless no command matches _p_a_t_t_e_r_n.

       hhiissttoorryy [[_n]]
       hhiissttoorryy --cc
       hhiissttoorryy --dd _o_f_f_s_e_t
       hhiissttoorryy --dd _s_t_a_r_t-_e_n_d
       hhiissttoorryy --aannrrww [_f_i_l_e_n_a_m_e]
       hhiissttoorryy --pp _a_r_g [_a_r_g ...]
       hhiissttoorryy --ss _a_r_g [_a_r_g ...]
              With no options, display the command history list with line num-
              bers.  Lines listed with a ** have been modified.  An argument of
              _n  lists only the last _n lines.  If the shell variable HHIISSTTTTIIMMEE--
              FFOORRMMAATT is set and not null, it is used as a  format  string  for
              _s_t_r_f_t_i_m_e(3)  to display the time stamp associated with each dis-
              played history entry.  No intervening blank is  printed  between
              the  formatted  time stamp and the history line.  If _f_i_l_e_n_a_m_e is
              supplied, it is used as the name of the history  file;  if  not,
              the  value of HHIISSTTFFIILLEE is used.  If _f_i_l_e_n_a_m_e is not supplied and
              HHIISSTTFFIILLEE is unset or null, the --aa,, --nn,, --rr,, and --ww  options  have
              no effect.  Options, if supplied, have the following meanings:
              --cc     Clear the history list by deleting all the entries.
              --dd _o_f_f_s_e_t
                     Delete  the  history entry at position _o_f_f_s_e_t.  If _o_f_f_s_e_t
                     is negative, it is interpreted as relative to one greater
                     than the last history position, so negative indices count
                     back from the end of the history,  and  an  index  of  -1
                     refers to the current hhiissttoorryy --dd command.
              --dd _s_t_a_r_t-_e_n_d
                     Delete  the  range  of  history entries between positions
                     _s_t_a_r_t and _e_n_d, inclusive.  Positive and  negative  values
                     for _s_t_a_r_t and _e_n_d are interpreted as described above.
              --aa     Append  the  "new"  history  lines  to  the history file.
                     These are history lines entered since  the  beginning  of
                     the current bbaasshh session, but not already appended to the
                     history file.
              --nn     Read  the history lines not already read from the history
                     file into the current history list.  These are lines  ap-
                     pended  to  the  history  file since the beginning of the
                     current bbaasshh session.
              --rr     Read the contents of the history file and append them  to
                     the current history list.
              --ww     Write the current history list to the history file, over-
                     writing the history file's contents.
              --pp     Perform  history  substitution  on the following _a_r_g_s and
                     display the result on  the  standard  output.   Does  not
                     store  the results in the history list.  Each _a_r_g must be
                     quoted to disable normal history expansion.
              --ss     Store the _a_r_g_s in the history list  as  a  single  entry.
                     The  last  command  in the history list is removed before
                     the _a_r_g_s are added.

              If the HHIISSTTTTIIMMEEFFOORRMMAATT variable is set, the time  stamp  informa-
              tion  associated  with each history entry is written to the his-
              tory file, marked with the history comment character.  When  the
              history  file  is read, lines beginning with the history comment
              character followed immediately by a  digit  are  interpreted  as
              timestamps for the following history entry.  The return value is
              0 unless an invalid option is encountered, an error occurs while
              reading  or writing the history file, an invalid _o_f_f_s_e_t or range
              is supplied as an argument to --dd, or the history expansion  sup-
              plied as an argument to --pp fails.

       jjoobbss [--llnnpprrss] [ _j_o_b_s_p_e_c ... ]
       jjoobbss --xx _c_o_m_m_a_n_d [ _a_r_g_s ... ]
              The first form lists the active jobs.  The options have the fol-
              lowing meanings:
              --ll     List process IDs in addition to the normal information.
              --nn     Display  information  only  about  jobs that have changed
                     status since the user was last notified of their status.
              --pp     List only the process  ID  of  the  job's  process  group
                     leader.
              --rr     Display only running jobs.
              --ss     Display only stopped jobs.

              If  _j_o_b_s_p_e_c  is given, output is restricted to information about
              that job.  The return status is 0 unless an  invalid  option  is
              encountered or an invalid _j_o_b_s_p_e_c is supplied.

              If the --xx option is supplied, jjoobbss replaces any _j_o_b_s_p_e_c found in
              _c_o_m_m_a_n_d or _a_r_g_s with the corresponding process group ID, and ex-
              ecutes _c_o_m_m_a_n_d passing it _a_r_g_s, returning its exit status.

       kkiillll [--ss _s_i_g_s_p_e_c | --nn _s_i_g_n_u_m | --_s_i_g_s_p_e_c] [_p_i_d | _j_o_b_s_p_e_c] ...
       kkiillll --ll|--LL [_s_i_g_s_p_e_c | _e_x_i_t___s_t_a_t_u_s]
              Send  the  signal  named  by  _s_i_g_s_p_e_c or _s_i_g_n_u_m to the processes
              named by _p_i_d or _j_o_b_s_p_e_c.  _s_i_g_s_p_e_c is either  a  case-insensitive
              signal  name such as SSIIGGKKIILLLL (with or without the SSIIGG prefix) or
              a signal number; _s_i_g_n_u_m is a signal number.  If _s_i_g_s_p_e_c  is  not
              present,  then  SSIIGGTTEERRMM is assumed.  An argument of --ll lists the
              signal names.  If any arguments are supplied when --ll  is  given,
              the  names  of  the  signals  corresponding to the arguments are
              listed, and the return status is 0.  The _e_x_i_t___s_t_a_t_u_s argument to
              --ll is a number specifying either a signal  number  or  the  exit
              status  of  a  process terminated by a signal.  The --LL option is
              equivalent to --ll.  kkiillll returns true if at least one signal  was
              successfully sent, or false if an error occurs or an invalid op-
              tion is encountered.

       lleett _a_r_g [_a_r_g ...]
              Each _a_r_g is an arithmetic expression to be evaluated (see AARRIITTHH--
              MMEETTIICC  EEVVAALLUUAATTIIOONN  above).   If the last _a_r_g evaluates to 0, lleett
              returns 1; 0 is returned otherwise.

       llooccaall [_o_p_t_i_o_n] [_n_a_m_e[=_v_a_l_u_e] ... | - ]
              For each argument, a local variable named _n_a_m_e is  created,  and
              assigned  _v_a_l_u_e.   The _o_p_t_i_o_n can be any of the options accepted
              by ddeeccllaarree.  When llooccaall is used within a function, it causes the
              variable _n_a_m_e to have a visible scope restricted to  that  func-
              tion  and  its children.  If _n_a_m_e is -, the set of shell options
              is made local to the function in which llooccaall is  invoked:  shell
              options  changed using the sseett builtin inside the function after
              the call to llooccaall are restored to their original values when the
              function returns.  The restore is effected as if a series of sseett
              commands were executed to restore the values that were in  place
              before  the  function.  With no operands, llooccaall writes a list of
              local variables to the standard output.  It is an error  to  use
              llooccaall when not within a function.  The return status is 0 unless
              llooccaall  is  used outside a function, an invalid _n_a_m_e is supplied,
              or _n_a_m_e is a readonly variable.

       llooggoouutt Exit a login shell.

       mmaappffiillee [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC
       _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y]
       rreeaaddaarrrraayy [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC
       _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y]
              Read lines from the standard input into the indexed array  vari-
              able  _a_r_r_a_y, or from file descriptor _f_d if the --uu option is sup-
              plied.  The variable MMAAPPFFIILLEE is the default _a_r_r_a_y.  Options,  if
              supplied, have the following meanings:
              --dd     The  first  character  of _d_e_l_i_m is used to terminate each
                     input line, rather than newline.  If _d_e_l_i_m is  the  empty
                     string, mmaappffiillee will terminate a line when it reads a NUL
                     character.
              --nn     Copy  at  most _c_o_u_n_t lines.  If _c_o_u_n_t is 0, all lines are
                     copied.
              --OO     Begin assigning to _a_r_r_a_y at index  _o_r_i_g_i_n.   The  default
                     index is 0.
              --ss     Discard the first _c_o_u_n_t lines read.
              --tt     Remove  a trailing _d_e_l_i_m (default newline) from each line
                     read.
              --uu     Read lines from file descriptor _f_d instead of  the  stan-
                     dard input.
              --CC     Evaluate  _c_a_l_l_b_a_c_k each time _q_u_a_n_t_u_m lines are read.  The
                     --cc option specifies _q_u_a_n_t_u_m.
              --cc     Specify the number of lines read  between  each  call  to
                     _c_a_l_l_b_a_c_k.

              If  --CC  is  specified  without  --cc, the default quantum is 5000.
              When _c_a_l_l_b_a_c_k is evaluated, it is supplied the index of the next
              array element to be assigned and the line to be assigned to that
              element as additional arguments.  _c_a_l_l_b_a_c_k  is  evaluated  after
              the line is read but before the array element is assigned.

              If  not supplied with an explicit origin, mmaappffiillee will clear _a_r_-
              _r_a_y before assigning to it.

              mmaappffiillee returns successfully unless an invalid option or  option
              argument  is  supplied,  _a_r_r_a_y is invalid or unassignable, or if
              _a_r_r_a_y is not an indexed array.

       ppooppdd [-nn] [+_n] [-_n]
              Removes entries from the directory stack.  The elements are num-
              bered from 0 starting at the first  directory  listed  by  ddiirrss.
              With  no  arguments,  ppooppdd  removes  the  top directory from the
              stack, and changes to the new top directory.  Arguments, if sup-
              plied, have the following meanings:
              --nn     Suppresses the normal change of directory  when  removing
                     directories from the stack, so that only the stack is ma-
                     nipulated.
              ++_n     Removes  the _nth entry counting from the left of the list
                     shown by ddiirrss, starting with zero, from the  stack.   For
                     example: "popd +0" removes the first directory, "popd +1"
                     the second.
              --_n     Removes the _nth entry counting from the right of the list
                     shown  by  ddiirrss,  starting with zero.  For example: "popd
                     -0" removes the last directory, "popd  -1"  the  next  to
                     last.

              If  the  top element of the directory stack is modified, and the
              _-_n option was not supplied, ppooppdd uses the ccdd builtin  to  change
              to the directory at the top of the stack.  If the ccdd fails, ppooppdd
              returns a non-zero value.

              Otherwise,  ppooppdd  returns  false if an invalid option is encoun-
              tered, the directory stack is empty, or a non-existent directory
              stack entry is specified.

              If the ppooppdd command is successful, bash runs ddiirrss  to  show  the
              final  contents of the directory stack, and the return status is
              0.

       pprriinnttff [--vv _v_a_r] _f_o_r_m_a_t [_a_r_g_u_m_e_n_t_s]
              Write the formatted _a_r_g_u_m_e_n_t_s to the standard output  under  the
              control  of  the  _f_o_r_m_a_t.  The --vv option causes the output to be
              assigned to the variable _v_a_r rather than being  printed  to  the
              standard output.

              The  _f_o_r_m_a_t  is a character string which contains three types of
              objects: plain characters, which are simply copied  to  standard
              output,  character  escape  sequences,  which  are converted and
              copied to the standard output, and format  specifications,  each
              of  which  causes  printing of the next successive _a_r_g_u_m_e_n_t.  In
              addition to the standard _p_r_i_n_t_f(3) format characters ccssnnddiioouuxxXXee--
              EEffFFggGGaaAA, pprriinnttff interprets the following additional format spec-
              ifiers:
              %%bb     causes pprriinnttff to expand backslash escape sequences in the
                     corresponding _a_r_g_u_m_e_n_t in the same way as eecchhoo --ee.
              %%qq     causes pprriinnttff to output the corresponding _a_r_g_u_m_e_n_t  in  a
                     format  that can be reused as shell input.  %%qq and %%QQ use
                     the $$'''' quoting style if any characters in  the  argument
                     string  require  it, and backslash quoting otherwise.  If
                     the format string uses the _p_r_i_n_t_f alternate  form,  these
                     two  formats  quote  the  argument  string  using  single
                     quotes.
              %%QQ     like %%qq, but applies any supplied precision to the  _a_r_g_u_-
                     _m_e_n_t before quoting it.
              %%((_d_a_t_e_f_m_t))TT
                     causes  pprriinnttff  to  output the date-time string resulting
                     from using _d_a_t_e_f_m_t as a format  string  for  _s_t_r_f_t_i_m_e(3).
                     The corresponding _a_r_g_u_m_e_n_t is an integer representing the
                     number  of seconds since the epoch.  Two special argument
                     values may be used: -1 represents the current  time,  and
                     -2  represents the time the shell was invoked.  If no ar-
                     gument is specified, conversion behaves as if -1 had been
                     given.  This is an exception to the usual  pprriinnttff  behav-
                     ior.

              The %b, %q, and %T format specifiers all use the field width and
              precision arguments from the format specification and write that
              many  bytes from (or use that wide a field for) the expanded ar-
              gument, which usually contains more characters than  the  origi-
              nal.

              The %n format specifier accepts a corresponding argument that is
              treated as a shell variable name.

              The  %s  and  %c  format specifiers accept an l (long) modifier,
              which forces them to convert the argument string to a wide-char-
              acter string and apply any supplied field width and precision in
              terms of characters, not bytes.

              Arguments to non-string format specifiers are treated as C  con-
              stants, except that a leading plus or minus sign is allowed, and
              if  the leading character is a single or double quote, the value
              is the ASCII value of the following character.

              The _f_o_r_m_a_t is reused as necessary to consume all  of  the  _a_r_g_u_-
              _m_e_n_t_s.  If the _f_o_r_m_a_t requires more _a_r_g_u_m_e_n_t_s than are supplied,
              the  extra  format  specifications  behave as if a zero value or
              null string, as appropriate,  had  been  supplied.   The  return
              value  is zero on success, non-zero if an invalid option is sup-
              plied or a write or assignment error occurs.

       ppuusshhdd [--nn] [+_n] [-_n]
       ppuusshhdd [--nn] [_d_i_r]
              Adds a directory to the top of the directory stack,  or  rotates
              the  stack,  making the new top of the stack the current working
              directory.  With no arguments, ppuusshhdd exchanges the top two  ele-
              ments  of the directory stack.  Arguments, if supplied, have the
              following meanings:
              --nn     Suppresses the normal change of directory  when  rotating
                     or  adding  directories  to  the  stack, so that only the
                     stack is manipulated.
              ++_n     Rotates the stack so that  the  _nth  directory  (counting
                     from  the  left  of the list shown by ddiirrss, starting with
                     zero) is at the top.
              --_n     Rotates the stack so that  the  _nth  directory  (counting
                     from  the  right of the list shown by ddiirrss, starting with
                     zero) is at the top.
              _d_i_r    Adds _d_i_r to the directory stack at the top

              After the stack has been modified, if the --nn option was not sup-
              plied, ppuusshhdd uses the ccdd builtin to change to the  directory  at
              the top of the stack.  If the ccdd fails, ppuusshhdd returns a non-zero
              value.

              Otherwise,  if no arguments are supplied, ppuusshhdd returns 0 unless
              the directory stack  is  empty.   When  rotating  the  directory
              stack,  ppuusshhdd returns 0 unless the directory stack is empty or a
              non-existent directory stack element is specified.

              If the ppuusshhdd command is successful, bash runs ddiirrss to  show  the
              final contents of the directory stack.

       ppwwdd [--LLPP]
              Print  the  absolute  pathname of the current working directory.
              The pathname printed contains no symbolic links if the --PP option
              is supplied or the --oo pphhyyssiiccaall option to the sseett builtin command
              is enabled.  If the --LL option is used, the pathname printed  may
              contain  symbolic links.  The return status is 0 unless an error
              occurs while reading the name of the current directory or an in-
              valid option is supplied.

       rreeaadd [--EEeerrss] [--aa _a_n_a_m_e] [--dd _d_e_l_i_m] [--ii _t_e_x_t] [--nn _n_c_h_a_r_s] [--NN _n_c_h_a_r_s]
       [--pp _p_r_o_m_p_t] [--tt _t_i_m_e_o_u_t] [--uu _f_d] [_n_a_m_e ...]
              One line is read from the standard input, or from the  file  de-
              scriptor _f_d supplied as an argument to the --uu option, split into
              words  as  described  above  under WWoorrdd SSpplliittttiinngg, and the first
              word is assigned to the first _n_a_m_e, the second word to the  sec-
              ond  _n_a_m_e,  and  so on.  If there are more words than names, the
              remaining words and their intervening delimiters are assigned to
              the last _n_a_m_e.  If there are fewer words  read  from  the  input
              stream  than  names, the remaining names are assigned empty val-
              ues.  The characters in IIFFSS are used  to  split  the  line  into
              words  using  the  same  rules the shell uses for expansion (de-
              scribed above under WWoorrdd SSpplliittttiinngg).   The  backslash  character
              (\\) may be used to remove any special meaning for the next char-
              acter  read  and  for  line continuation.  Options, if supplied,
              have the following meanings:
              --aa _a_n_a_m_e
                     The words are assigned to sequential indices of the array
                     variable _a_n_a_m_e, starting at 0.  _a_n_a_m_e is unset before any
                     new values are assigned.  Other _n_a_m_e  arguments  are  ig-
                     nored.
              --dd _d_e_l_i_m
                     The first character of _d_e_l_i_m is used to terminate the in-
                     put  line,  rather  than  newline.  If _d_e_l_i_m is the empty
                     string, rreeaadd will terminate a line when it  reads  a  NUL
                     character.
              --ee     If  the  standard  input  is coming from a terminal, rreeaadd
                     uses rreeaaddlliinnee (see RREEAADDLLIINNEE above) to  obtain  the  line.
                     Readline  uses  the  current (or default, if line editing
                     was not previously active)  editing  settings,  but  uses
                     readline's default filename completion.
              --EE     If  the  standard  input  is coming from a terminal, rreeaadd
                     uses rreeaaddlliinnee (see RREEAADDLLIINNEE above) to  obtain  the  line.
                     Readline  uses  the  current (or default, if line editing
                     was not previously active)  editing  settings,  but  uses
                     bash's default completion, including programmable comple-
                     tion.
              --ii _t_e_x_t
                     If  rreeaaddlliinnee  is  being  used  to  read the line, _t_e_x_t is
                     placed into the editing buffer before editing begins.
              --nn _n_c_h_a_r_s
                     rreeaadd returns after reading _n_c_h_a_r_s characters rather  than
                     waiting for a complete line of input, but honors a delim-
                     iter  if fewer than _n_c_h_a_r_s characters are read before the
                     delimiter.
              --NN _n_c_h_a_r_s
                     rreeaadd returns  after  reading  exactly  _n_c_h_a_r_s  characters
                     rather  than waiting for a complete line of input, unless
                     EOF is encountered or rreeaadd times out.  Delimiter  charac-
                     ters  encountered  in the input are not treated specially
                     and do not cause rreeaadd to return until  _n_c_h_a_r_s  characters
                     are  read.   The result is not split on the characters in
                     IIFFSS; the intent is that the variable is assigned  exactly
                     the characters read (with the exception of backslash; see
                     the --rr option below).
              --pp _p_r_o_m_p_t
                     Display _p_r_o_m_p_t on standard error, without a trailing new-
                     line, before attempting to read any input.  The prompt is
                     displayed only if input is coming from a terminal.
              --rr     Backslash does not act as an escape character.  The back-
                     slash  is considered to be part of the line.  In particu-
                     lar, a backslash-newline pair may not then be used  as  a
                     line continuation.
              --ss     Silent mode.  If input is coming from a terminal, charac-
                     ters are not echoed.
              --tt _t_i_m_e_o_u_t
                     Cause  rreeaadd  to time out and return failure if a complete
                     line of input (or a specified number  of  characters)  is
                     not  read within _t_i_m_e_o_u_t seconds.  _t_i_m_e_o_u_t may be a deci-
                     mal number with a fractional portion following the  deci-
                     mal  point.   This  option  is  only effective if rreeaadd is
                     reading input from a terminal,  pipe,  or  other  special
                     file;  it  has no effect when reading from regular files.
                     If rreeaadd times out, rreeaadd saves any partial input read into
                     the specified variable _n_a_m_e.  If _t_i_m_e_o_u_t is 0,  rreeaadd  re-
                     turns  immediately, without trying to read any data.  The
                     exit status is 0 if input is available on  the  specified
                     file  descriptor,  or  the read will return EOF, non-zero
                     otherwise.  The exit status is greater than  128  if  the
                     timeout is exceeded.
              --uu _f_d  Read input from file descriptor _f_d.

              Other  than  the  case where _d_e_l_i_m is the empty string, rreeaadd ig-
              nores any NUL characters in the input.

              If no _n_a_m_e_s are supplied, the line read, without the ending  de-
              limiter  but  otherwise  unmodified, is assigned to the variable
              RREEPPLLYY.  The exit status is zero, unless end-of-file  is  encoun-
              tered,  rreeaadd times out (in which case the status is greater than
              128), a variable assignment error (such as assigning to a  read-
              only variable) occurs, or an invalid file descriptor is supplied
              as the argument to --uu.

       rreeaaddoonnllyy [--aaAAff] [--pp] [_n_a_m_e[=_w_o_r_d] ...]
              The  given  _n_a_m_e_s are marked readonly; the values of these _n_a_m_e_s
              may not be changed by subsequent assignment.  If the  --ff  option
              is  supplied,  the  functions  corresponding to the _n_a_m_e_s are so
              marked.  The --aa option restricts the variables  to  indexed  ar-
              rays;  the  --AA option restricts the variables to associative ar-
              rays.  If both options are supplied, --AA takes precedence.  If no
              _n_a_m_e arguments are given, or if the --pp  option  is  supplied,  a
              list of all readonly names is printed.  The other options may be
              used  to  restrict the output to a subset of the set of readonly
              names.  The --pp option causes output to be displayed in a  format
              that  may be reused as input.  If a variable name is followed by
              =_w_o_r_d, the value of the variable is set  to  _w_o_r_d.   The  return
              status  is 0 unless an invalid option is encountered, one of the
              _n_a_m_e_s is not a valid shell variable name, or --ff is supplied with
              a _n_a_m_e that is not a function.

       rreettuurrnn [_n]
              Causes a function to stop executing and return the value  speci-
              fied  by _n to its caller.  If _n is omitted, the return status is
              that of the last command executed in the function body.  If  rree--
              ttuurrnn is executed by a trap handler, the last command used to de-
              termine  the status is the last command executed before the trap
              handler.  If rreettuurrnn is executed during a DDEEBBUUGG  trap,  the  last
              command  used  to  determine the status is the last command exe-
              cuted by the trap handler before rreettuurrnn was invoked.  If  rreettuurrnn
              is  used outside a function, but during execution of a script by
              the ..  (ssoouurrccee) command, it causes the shell to  stop  executing
              that  script  and return either _n or the exit status of the last
              command executed within the script as the  exit  status  of  the
              script.  If _n is supplied, the return value is its least signif-
              icant  8  bits.  The return status is non-zero if rreettuurrnn is sup-
              plied a non-numeric argument, or is used outside a function  and
              not  during  execution  of a script by .. or ssoouurrccee.  Any command
              associated with the RREETTUURRNN trap is executed before execution re-
              sumes after the function or script.

       sseett [--aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [--oo _o_p_t_i_o_n_-_n_a_m_e] [----] [--] [_a_r_g ...]
       sseett [++aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [++oo _o_p_t_i_o_n_-_n_a_m_e] [----] [--] [_a_r_g ...]
       sseett --oo
       sseett ++oo Without options, display the name and value of each shell  vari-
              able  in a format that can be reused as input for setting or re-
              setting the currently-set variables.  Read-only variables cannot
              be reset.  In _p_o_s_i_x _m_o_d_e, only shell variables are listed.   The
              output  is sorted according to the current locale.  When options
              are specified, they set or unset shell  attributes.   Any  argu-
              ments  remaining  after  option processing are treated as values
              for the positional parameters and are assigned, in order, to $$11,
              $$22, ..., $$_n.  Options, if specified, have  the  following  mean-
              ings:
              --aa      Each variable or function that is created or modified is
                      given  the export attribute and marked for export to the
                      environment of subsequent commands.
              --bb      Report the status of terminated background jobs  immedi-
                      ately, rather than before the next primary prompt.  This
                      is effective only when job control is enabled.
              --ee      Exit  immediately  if a _p_i_p_e_l_i_n_e (which may consist of a
                      single _s_i_m_p_l_e _c_o_m_m_a_n_d), a _l_i_s_t, or  a  _c_o_m_p_o_u_n_d  _c_o_m_m_a_n_d
                      (see SSHHEELLLL GGRRAAMMMMAARR above), exits with a non-zero status.
                      The  shell  does  not  exit if the command that fails is
                      part of the command list immediately following  a  wwhhiillee
                      or  uunnttiill  keyword, part of the test following the iiff or
                      eelliiff reserved words, part of any command executed  in  a
                      &&&&  or |||| list except the command following the final &&&&
                      or ||||, any command in a pipeline but the last, or if the
                      command's return value is being inverted with !!.   If  a
                      compound  command  other  than a subshell returns a non-
                      zero status because a command failed while --ee was  being
                      ignored,  the  shell  does  not exit.  A trap on EERRRR, if
                      set, is executed before the shell  exits.   This  option
                      applies to the shell environment and each subshell envi-
                      ronment  separately  (see  CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT
                      above), and may cause subshells to exit before executing
                      all the commands in the subshell.

                      If a compound command or shell function  executes  in  a
                      context  where --ee is being ignored, none of the commands
                      executed within the compound command  or  function  body
                      will  be  affected  by the --ee setting, even if --ee is set
                      and a command returns a failure status.  If  a  compound
                      command  or  shell function sets --ee while executing in a
                      context where --ee is ignored, that setting will not  have
                      any  effect  until  the  compound command or the command
                      containing the function call completes.
              --ff      Disable pathname expansion.
              --hh      Remember the location of commands as they are looked  up
                      for execution.  This is enabled by default.
              --kk      All  arguments  in the form of assignment statements are
                      placed in the environment for a command, not just  those
                      that precede the command name.
              --mm      Monitor  mode.   Job control is enabled.  This option is
                      on by default for interactive  shells  on  systems  that
                      support  it  (see JJOOBB CCOONNTTRROOLL above).  All processes run
                      in a separate process group.  When a background job com-
                      pletes, the shell prints a line containing its exit sta-
                      tus.
              --nn      Read commands but do not execute them.  This may be used
                      to check a shell script for syntax errors.  This is  ig-
                      nored by interactive shells.
              --oo _o_p_t_i_o_n_-_n_a_m_e
                      The _o_p_t_i_o_n_-_n_a_m_e can be one of the following:
                      aalllleexxppoorrtt
                              Same as --aa.
                      bbrraacceeeexxppaanndd
                              Same as --BB.
                      eemmaaccss   Use  an  emacs-style command line editing inter-
                              face.  This is enabled by default when the shell
                              is interactive, unless the shell is started with
                              the ----nnooeeddiittiinngg option.  This also  affects  the
                              editing interface used for rreeaadd --ee.
                      eerrrreexxiitt Same as --ee.
                      eerrrrttrraaccee
                              Same as --EE.
                      ffuunnccttrraaccee
                              Same as --TT.
                      hhaasshhaallll Same as --hh.
                      hhiisstteexxppaanndd
                              Same as --HH.
                      hhiissttoorryy Enable command history, as described above under
                              HHIISSTTOORRYY.  This option is on by default in inter-
                              active shells.
                      iiggnnoorreeeeooff
                              The   effect   is   as   if  the  shell  command
                              "IGNOREEOF=10"  had  been  executed  (see  SShheellll
                              VVaarriiaabblleess above).
                      kkeeyywwoorrdd Same as --kk.
                      mmoonniittoorr Same as --mm.
                      nnoocclloobbbbeerr
                              Same as --CC.
                      nnooeexxeecc  Same as --nn.
                      nnoogglloobb  Same as --ff.
                      nnoolloogg   Currently ignored.
                      nnoottiiffyy  Same as --bb.
                      nnoouunnsseett Same as --uu.
                      oonneeccmmdd  Same as --tt.
                      pphhyyssiiccaall
                              Same as --PP.
                      ppiippeeffaaiill
                              If  set,  the  return value of a pipeline is the
                              value of the last (rightmost)  command  to  exit
                              with  a non-zero status, or zero if all commands
                              in the pipeline exit successfully.  This  option
                              is disabled by default.
                      ppoossiixx   Change  the  behavior  of bbaasshh where the default
                              operation differs from  the  POSIX  standard  to
                              match  the  standard (_p_o_s_i_x _m_o_d_e).  See SSEEEE AALLSSOO
                              below for a reference to a document that details
                              how posix mode affects bash's behavior.
                      pprriivviilleeggeedd
                              Same as --pp.
                      vveerrbboossee Same as --vv.
                      vvii      Use a vi-style command line  editing  interface.
                              This also affects the editing interface used for
                              rreeaadd --ee.
                      xxttrraaccee  Same as --xx.
                      If  --oo  is  supplied with no _o_p_t_i_o_n_-_n_a_m_e, sseett prints the
                      current shell option settings.  If ++oo is  supplied  with
                      no  _o_p_t_i_o_n_-_n_a_m_e,  sseett prints a series of sseett commands to
                      recreate the current option  settings  on  the  standard
                      output.
              --pp      Turn  on  _p_r_i_v_i_l_e_g_e_d  mode.   In this mode, the $$EENNVV and
                      $$BBAASSHH__EENNVV files are not processed, shell  functions  are
                      not  inherited  from the environment, and the SSHHEELLLLOOPPTTSS,
                      BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they  ap-
                      pear  in  the environment, are ignored.  If the shell is
                      started with the effective user (group) id not equal  to
                      the  real user (group) id, and the --pp option is not sup-
                      plied, these actions are taken and the effective user id
                      is set to the real user id.  If the --pp  option  is  sup-
                      plied  at  startup,  the effective user id is not reset.
                      Turning this option off causes the  effective  user  and
                      group ids to be set to the real user and group ids.
              --rr      Enable restricted shell mode.  This option cannot be un-
                      set once it has been set.
              --tt      Exit after reading and executing one command.
              --uu      Treat unset variables and parameters other than the spe-
                      cial  parameters  "@"  and  "*", or array variables sub-
                      scripted with "@" or "*", as an  error  when  performing
                      parameter  expansion.   If  expansion is attempted on an
                      unset variable or parameter, the shell prints  an  error
                      message,  and, if not interactive, exits with a non-zero
                      status.
              --vv      Print shell input lines as they are read.
              --xx      After expanding each _s_i_m_p_l_e _c_o_m_m_a_n_d, ffoorr  command,  ccaassee
                      command, sseelleecctt command, or arithmetic ffoorr command, dis-
                      play  the expanded value of PPSS44, followed by the command
                      and its expanded arguments or associated word  list,  to
                      standard error.
              --BB      The  shell performs brace expansion (see BBrraaccee EExxppaannssiioonn
                      above).  This is on by default.
              --CC      If set, bbaasshh does not overwrite an  existing  file  with
                      the  >>,  >>&&,  and <<>> redirection operators.  This may be
                      overridden when creating output files by using the redi-
                      rection operator >>|| instead of >>.
              --EE      If set, any trap on EERRRR is inherited by shell functions,
                      command substitutions, and commands executed in  a  sub-
                      shell  environment.  The EERRRR trap is normally not inher-
                      ited in such cases.
              --HH      Enable !!  style history substitution.  This option is on
                      by default when the shell is interactive.
              --PP      If set, the shell does not resolve symbolic  links  when
                      executing  commands  such  as ccdd that change the current
                      working  directory.   It  uses  the  physical  directory
                      structure instead.  By default, bbaasshh follows the logical
                      chain  of  directories  when  performing  commands which
                      change the current directory.
              --TT      If set, any traps on DDEEBBUUGG and RREETTUURRNN are  inherited  by
                      shell functions, command substitutions, and commands ex-
                      ecuted  in a subshell environment.  The DDEEBBUUGG and RREETTUURRNN
                      traps are normally not inherited in such cases.
              ----      If no arguments follow this option, then the  positional
                      parameters are unset.  Otherwise, the positional parame-
                      ters  are  set  to  the _a_r_gs, even if some of them begin
                      with a --.
              --       Signal the end of options, cause all remaining  _a_r_gs  to
                      be assigned to the positional parameters.  The --xx and --vv
                      options are turned off.  If there are no _a_r_gs, the posi-
                      tional parameters remain unchanged.

              The  options are off by default unless otherwise noted.  Using +
              rather than - causes these options to be turned  off.   The  op-
              tions can also be specified as arguments to an invocation of the
              shell.   The current set of options may be found in $$--.  The re-
              turn status is always true unless an invalid option  is  encoun-
              tered.

       sshhiifftt [_n]
              The  positional  parameters  from _n+1 ... are renamed to $$11 ........
              Parameters represented by the numbers $$## down to $$##-_n+1 are  un-
              set.   _n must be a non-negative number less than or equal to $$##.
              If _n is 0, no parameters are changed.  If _n is not given, it  is
              assumed  to be 1.  If _n is greater than $$##, the positional para-
              meters are not changed.  The return status is greater than  zero
              if _n is greater than $$## or less than zero; otherwise 0.

       sshhoopptt [--ppqqssuu] [--oo] [_o_p_t_n_a_m_e ...]
              Toggle  the values of settings controlling optional shell behav-
              ior.  The settings can be either those listed below, or, if  the
              --oo option is used, those available with the --oo option to the sseett
              builtin command.  With no options, or with the --pp option, a list
              of  all  settable  options  is  displayed, with an indication of
              whether or not each is set; if _o_p_t_n_a_m_e_s are supplied, the output
              is restricted to those options.  The --pp option causes output  to
              be  displayed  in a form that may be reused as input.  Other op-
              tions have the following meanings:
              --ss     Enable (set) each _o_p_t_n_a_m_e.
              --uu     Disable (unset) each _o_p_t_n_a_m_e.
              --qq     Suppresses normal output (quiet mode); the return  status
                     indicates whether the _o_p_t_n_a_m_e is set or unset.  If multi-
                     ple  _o_p_t_n_a_m_e arguments are given with --qq, the return sta-
                     tus is zero if all _o_p_t_n_a_m_e_s are enabled; non-zero  other-
                     wise.
              --oo     Restricts  the  values of _o_p_t_n_a_m_e to be those defined for
                     the --oo option to the sseett builtin.

              If either --ss or --uu is used  with  no  _o_p_t_n_a_m_e  arguments,  sshhoopptt
              shows  only  those options which are set or unset, respectively.
              Unless otherwise noted, the sshhoopptt options are  disabled  (unset)
              by default.

              The  return  status when listing options is zero if all _o_p_t_n_a_m_e_s
              are enabled, non-zero otherwise.  When setting or unsetting  op-
              tions,  the  return  status  is  zero unless an _o_p_t_n_a_m_e is not a
              valid shell option.

              The list of sshhoopptt options is:

              aarrrraayy__eexxppaanndd__oonnccee
                      If set, the shell suppresses multiple evaluation of  as-
                      sociative and indexed array subscripts during arithmetic
                      expression evaluation, while executing builtins that can
                      perform   variable   assignments,  and  while  executing
                      builtins that perform array dereferencing.
              aassssoocc__eexxppaanndd__oonnccee
                      Deprecated; a synonym for aarrrraayy__eexxppaanndd__oonnccee.
              aauuttooccdd  If set, a command name that is the name of  a  directory
                      is  executed  as  if it were the argument to the ccdd com-
                      mand.  This option is only used by interactive shells.
              ccddaabbllee__vvaarrss
                      If set, an argument to the ccdd builtin  command  that  is
                      not  a directory is assumed to be the name of a variable
                      whose value is the directory to change to.
              ccddssppeellll If set, minor errors in the spelling of a directory com-
                      ponent in a ccdd command will be  corrected.   The  errors
                      checked for are transposed characters, a missing charac-
                      ter,  and  one  character  too many.  If a correction is
                      found, the corrected filename is printed, and  the  com-
                      mand  proceeds.  This option is only used by interactive
                      shells.
              cchheecckkhhaasshh
                      If set, bbaasshh checks that a command found in the hash ta-
                      ble exists before trying to execute  it.   If  a  hashed
                      command  no  longer exists, a normal path search is per-
                      formed.
              cchheecckkjjoobbss
                      If set, bbaasshh lists the status of any stopped and running
                      jobs before exiting an interactive shell.  If  any  jobs
                      are running, this causes the exit to be deferred until a
                      second  exit is attempted without an intervening command
                      (see JJOOBB CCOONNTTRROOLL above).  The shell always postpones ex-
                      iting if any jobs are stopped.
              cchheecckkwwiinnssiizzee
                      If set, bbaasshh checks the window size after each  external
                      (non-builtin)  command  and,  if  necessary, updates the
                      values of LLIINNEESS and CCOOLLUUMMNNSS.  This option is enabled  by
                      default.
              ccmmddhhiisstt If  set,  bbaasshh attempts to save all lines of a multiple-
                      line command in the same  history  entry.   This  allows
                      easy  re-editing of multi-line commands.  This option is
                      enabled by default, but only has an  effect  if  command
                      history is enabled, as described above under HHIISSTTOORRYY.
              ccoommppaatt3311
              ccoommppaatt3322
              ccoommppaatt4400
              ccoommppaatt4411
              ccoommppaatt4422
              ccoommppaatt4433
              ccoommppaatt4444
              ccoommppaatt5500
                      These  control aspects of the shell's compatibility mode
                      (see SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below).

              ccoommpplleettee__ffuullllqquuoottee
                      If set, bbaasshh quotes all shell  metacharacters  in  file-
                      names  and  directory  names when performing completion.
                      If not set, bbaasshh removes metacharacters such as the dol-
                      lar sign from the set of characters that will be  quoted
                      in  completed filenames when these metacharacters appear
                      in shell variable references in words to  be  completed.
                      This  means that dollar signs in variable names that ex-
                      pand to directories will not  be  quoted;  however,  any
                      dollar  signs appearing in filenames will not be quoted,
                      either.  This is active only when bash  is  using  back-
                      slashes  to quote completed filenames.  This variable is
                      set by default, which is the default  bash  behavior  in
                      versions through 4.2.

              ddiirreexxppaanndd
                      If  set,  bbaasshh replaces directory names with the results
                      of word expansion when performing  filename  completion.
                      This  changes  the  contents  of  the  readline  editing
                      buffer.  If not set, bbaasshh attempts to preserve what  the
                      user typed.

              ddiirrssppeellll
                      If  set,  bbaasshh attempts spelling correction on directory
                      names during word completion if the directory name  ini-
                      tially supplied does not exist.

              ddoottgglloobb If  set, bbaasshh includes filenames beginning with a "." in
                      the results of pathname expansion.   The  filenames  "."
                      and ".." must always be matched explicitly, even if ddoott--
                      gglloobb is set.

              eexxeeccffaaiill
                      If set, a non-interactive shell will not exit if it can-
                      not  execute  the  file  specified as an argument to the
                      eexxeecc builtin command.  An  interactive  shell  does  not
                      exit if eexxeecc fails.

              eexxppaanndd__aalliiaasseess
                      If  set,  aliases  are expanded as described above under
                      AALLIIAASSEESS.  This option is enabled by default for interac-
                      tive shells.

              eexxttddeebbuugg
                      If set at shell invocation, or in a shell startup  file,
                      arrange to execute the debugger profile before the shell
                      starts,  identical to the ----ddeebbuuggggeerr option.  If set af-
                      ter invocation, behavior intended for use  by  debuggers
                      is enabled:

                      11..     The --FF option to the ddeeccllaarree builtin displays the
                             source file name and line number corresponding to
                             each function name supplied as an argument.

                      22..     If  the  command  run by the DDEEBBUUGG trap returns a
                             non-zero value, the next command is  skipped  and
                             not executed.

                      33..     If  the  command  run by the DDEEBBUUGG trap returns a
                             value of 2, and the shell is executing in a  sub-
                             routine  (a shell function or a shell script exe-
                             cuted by the .. or  ssoouurrccee  builtins),  the  shell
                             simulates a call to rreettuurrnn.

                      44..     BBAASSHH__AARRGGCC  and BBAASSHH__AARRGGVV are updated as described
                             in their descriptions above).

                      55..     Function tracing is  enabled:  command  substitu-
                             tion, shell functions, and subshells invoked with
                             (( _c_o_m_m_a_n_d )) inherit the DDEEBBUUGG and RREETTUURRNN traps.

                      66..     Error  tracing  is enabled: command substitution,
                             shell functions, and  subshells  invoked  with  ((
                             _c_o_m_m_a_n_d )) inherit the EERRRR trap.

              eexxttgglloobb If set, the extended pattern matching features described
                      above under PPaatthhnnaammee EExxppaannssiioonn are enabled.

              eexxttqquuoottee
                      If  set,  $$'_s_t_r_i_n_g'  and  $$"_s_t_r_i_n_g" quoting is performed
                      within  $${{_p_a_r_a_m_e_t_e_r}}  expansions  enclosed   in   double
                      quotes.  This option is enabled by default.

              ffaaiillgglloobb
                      If  set,  patterns  which fail to match filenames during
                      pathname expansion result in an expansion error.

              ffoorrccee__ffiiggnnoorree
                      If set, the suffixes  specified  by  the  FFIIGGNNOORREE  shell
                      variable  cause words to be ignored when performing word
                      completion even if the ignored words are the only possi-
                      ble completions.  See SSHHEELLLL VVAARRIIAABBLLEESS above  for  a  de-
                      scription  of  FFIIGGNNOORREE.   This  option is enabled by de-
                      fault.

              gglloobbaasscciiiirraannggeess
                      If set,  range  expressions  used  in  pattern  matching
                      bracket  expressions (see PPaatttteerrnn MMaattcchhiinngg above) behave
                      as if in the traditional C locale when  performing  com-
                      parisons.   That  is, the current locale's collating se-
                      quence is not taken into account, so bb will not  collate
                      between  AA  and  BB,  and upper-case and lower-case ASCII
                      characters will collate together.

              gglloobbsskkiippddoottss
                      If set, pathname expansion will never  match  the  file-
                      names  "."  and  "..", even if the pattern begins with a
                      ".".  This option is enabled by default.

              gglloobbssttaarr
                      If set, the pattern **** used in a pathname expansion con-
                      text will match all files and zero or  more  directories
                      and  subdirectories.  If the pattern is followed by a //,
                      only directories and subdirectories match.

              ggnnuu__eerrrrffmmtt
                      If set, shell error messages are written in the standard
                      GNU error message format.

              hhiissttaappppeenndd
                      If set, the history list is appended to the  file  named
                      by the value of the HHIISSTTFFIILLEE variable when the shell ex-
                      its, rather than overwriting the file.

              hhiissttrreeeeddiitt
                      If  set, and rreeaaddlliinnee is being used, a user is given the
                      opportunity to re-edit a failed history substitution.

              hhiissttvveerriiffyy
                      If set, and rreeaaddlliinnee is being used, the results of  his-
                      tory  substitution  are  not  immediately  passed to the
                      shell parser.  Instead, the  resulting  line  is  loaded
                      into the rreeaaddlliinnee editing buffer, allowing further modi-
                      fication.

              hhoossttccoommpplleettee
                      If set, and rreeaaddlliinnee is being used, bbaasshh will attempt to
                      perform  hostname  completion when a word containing a @@
                      is  being  completed  (see  CCoommpplleettiinngg  under   RREEAADDLLIINNEE
                      above).  This is enabled by default.

              hhuuppoonneexxiitt
                      If set, bbaasshh will send SSIIGGHHUUPP to all jobs when an inter-
                      active login shell exits.

              iinnhheerriitt__eerrrreexxiitt
                      If  set,  command substitution inherits the value of the
                      eerrrreexxiitt option, instead of unsetting it in the  subshell
                      environment.   This option is enabled when _p_o_s_i_x _m_o_d_e is
                      enabled.

              iinntteerraaccttiivvee__ccoommmmeennttss
                      If set, allow a word beginning with ## to cause that word
                      and all remaining characters on that line to be  ignored
                      in  an interactive shell (see CCOOMMMMEENNTTSS above).  This op-
                      tion is enabled by default.

              llaassttppiippee
                      If set, and job control is not active,  the  shell  runs
                      the last command of a pipeline not executed in the back-
                      ground in the current shell environment.

              lliitthhiisstt If  set,  and  the ccmmddhhiisstt option is enabled, multi-line
                      commands are saved to the history with embedded newlines
                      rather than using semicolon separators where possible.

              llooccaallvvaarr__iinnhheerriitt
                      If set, local variables inherit the value and attributes
                      of a variable of the same name that exists at a previous
                      scope before any new value is assigned.  The nameref at-
                      tribute is not inherited.

              llooccaallvvaarr__uunnsseett
                      If set, calling uunnsseett on  local  variables  in  previous
                      function  scopes  marks  them so subsequent lookups find
                      them unset until that function returns. This is  identi-
                      cal  to the behavior of unsetting local variables at the
                      current function scope.

              llooggiinn__sshheellll
                      The shell sets this option if it is started as  a  login
                      shell  (see  IINNVVOOCCAATTIIOONN  above).   The  value may not be
                      changed.

              mmaaiillwwaarrnn
                      If set, and a file that bbaasshh is checking  for  mail  has
                      been  accessed  since the last time it was checked, bbaasshh
                      displays the message "The  mail  in  _m_a_i_l_f_i_l_e  has  been
                      read".

              nnoo__eemmppttyy__ccmmdd__ccoommpplleettiioonn
                      If  set,  and  rreeaaddlliinnee is being used, bbaasshh will not at-
                      tempt to search the PPAATTHH for possible  completions  when
                      completion is attempted on an empty line.

              nnooccaasseegglloobb
                      If  set,  bbaasshh  matches  filenames in a case-insensitive
                      fashion when performing pathname expansion (see PPaatthhnnaammee
                      EExxppaannssiioonn above).

              nnooccaasseemmaattcchh
                      If set, bbaasshh  matches  patterns  in  a  case-insensitive
                      fashion when performing matching while executing ccaassee or
                      [[[[ conditional commands, when performing pattern substi-
                      tution  word expansions, or when filtering possible com-
                      pletions as part of programmable completion.

              nnooeexxppaanndd__ttrraannssllaattiioonn
                      If set, bbaasshh encloses the translated results  of  $$""...""
                      quoting  in  single quotes instead of double quotes.  If
                      the string is not translated, this has no effect.

              nnuullllgglloobb
                      If set, pathname expansion patterns which match no files
                      (see PPaatthhnnaammee EExxppaannssiioonn above) expand to nothing and are
                      removed, rather than expanding to themselves.

              ppaattssuubb__rreeppllaacceemmeenntt
                      If set, bbaasshh expands occurrences of && in the replacement
                      string of pattern substitution to the  text  matched  by
                      the  pattern,  as  described  under  PPaarraammeetteerr EExxppaannssiioonn
                      above.  This option is enabled by default.

              pprrooggccoommpp
                      If set, the programmable completion facilities (see PPrroo--
                      ggrraammmmaabbllee CCoommpplleettiioonn above) are enabled.  This option is
                      enabled by default.

              pprrooggccoommpp__aalliiaass
                      If set, and programmable  completion  is  enabled,  bbaasshh
                      treats  a command name that doesn't have any completions
                      as a possible alias and attempts alias expansion. If  it
                      has  an alias, bbaasshh attempts programmable completion us-
                      ing the command word resulting from the expanded alias.

              pprroommppttvvaarrss
                      If set, prompt strings undergo parameter expansion, com-
                      mand substitution, arithmetic expansion, and  quote  re-
                      moval  after  being  expanded  as described in PPRROOMMPPTTIINNGG
                      above.  This option is enabled by default.

              rreessttrriicctteedd__sshheellll
                      The shell sets this option  if  it  is  started  in  re-
                      stricted  mode  (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).  The value
                      may not be changed.  This is not reset when the  startup
                      files  are  executed, allowing the startup files to dis-
                      cover whether or not a shell is restricted.

              sshhiifftt__vveerrbboossee
                      If set, the sshhiifftt builtin prints an error  message  when
                      the shift count exceeds the number of positional parame-
                      ters.

              ssoouurrcceeppaatthh
                      If set, the .. (ssoouurrccee) builtin uses the value of PPAATTHH to
                      find  the  directory  containing the file supplied as an
                      argument when the --pp option is not supplied.   This  op-
                      tion is enabled by default.

              vvaarrrreeddiirr__cclloossee
                      If  set, the shell automatically closes file descriptors
                      assigned using the  _{_v_a_r_n_a_m_e_}  redirection  syntax  (see
                      RREEDDIIRREECCTTIIOONN above) instead of leaving them open when the
                      command completes.

              xxppgg__eecchhoo
                      If  set,  the  eecchhoo builtin expands backslash-escape se-
                      quences by default.  If the ppoossiixx shell option  is  also
                      enabled, eecchhoo does not interpret any options.

       ssuussppeenndd [--ff]
              Suspend  the execution of this shell until it receives a SSIIGGCCOONNTT
              signal.  A login shell, or a shell without job control  enabled,
              cannot  be suspended; the --ff option can be used to override this
              and force the suspension.  The return status  is  0  unless  the
              shell  is  a login shell or job control is not enabled and --ff is
              not supplied.

       tteesstt _e_x_p_r
       [[ _e_x_p_r ]]
              Return a status of 0 (true) or 1 (false) depending on the evalu-
              ation of the conditional expression  _e_x_p_r.   Each  operator  and
              operand  must  be a separate argument.  Expressions are composed
              of the primaries described above under CCOONNDDIITTIIOONNAALL  EEXXPPRREESSSSIIOONNSS.
              tteesstt  does not accept any options, nor does it accept and ignore
              an argument of ---- as signifying the end of options.

              Expressions may  be  combined  using  the  following  operators,
              listed  in  decreasing  order of precedence.  The evaluation de-
              pends on the number of arguments; see  below.   Operator  prece-
              dence is used when there are five or more arguments.
              !! _e_x_p_r True if _e_x_p_r is false.
              (( _e_x_p_r ))
                     Returns  the value of _e_x_p_r.  This may be used to override
                     the normal precedence of operators.
              _e_x_p_r_1 -aa _e_x_p_r_2
                     True if both _e_x_p_r_1 and _e_x_p_r_2 are true.
              _e_x_p_r_1 -oo _e_x_p_r_2
                     True if either _e_x_p_r_1 or _e_x_p_r_2 is true.

              tteesstt and [[ evaluate conditional expressions using a set of rules
              based on the number of arguments.

              0 arguments
                     The expression is false.
              1 argument
                     The expression is true if and only if the argument is not
                     null.
              2 arguments
                     If the first argument is !!, the expression is true if and
                     only if the second argument is null.  If the first  argu-
                     ment  is  one  of  the unary conditional operators listed
                     above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS,  the  expression  is
                     true if the unary test is true.  If the first argument is
                     not a valid unary conditional operator, the expression is
                     false.
              3 arguments
                     The following conditions are applied in the order listed.
                     If  the  second argument is one of the binary conditional
                     operators listed above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the
                     result of the expression is the result of the binary test
                     using the first and third arguments as operands.  The  --aa
                     and  --oo  operators  are  considered binary operators when
                     there are three arguments.  If the first argument  is  !!,
                     the  value is the negation of the two-argument test using
                     the second and third arguments.  If the first argument is
                     exactly (( and the third argument is exactly )), the result
                     is the one-argument test of the second argument.   Other-
                     wise, the expression is false.
              4 arguments
                     The following conditions are applied in the order listed.
                     If the first argument is !!, the result is the negation of
                     the  three-argument  expression composed of the remaining
                     arguments.  the two-argument test using  the  second  and
                     third  arguments.  If the first argument is exactly (( and
                     the fourth argument is exactly )), the result is the  two-
                     argument  test of the second and third arguments.  Other-
                     wise, the expression is parsed and evaluated according to
                     precedence using the rules listed above.
              5 or more arguments
                     The expression  is  parsed  and  evaluated  according  to
                     precedence using the rules listed above.

              When the shell is in _p_o_s_i_x _m_o_d_e, or if the expression is part of
              the [[[[ command, the << and >> operators sort using the current lo-
              cale.   If  the  shell is not in _p_o_s_i_x _m_o_d_e, the tteesstt and [[ com-
              mands sort lexicographically using ASCII ordering.

       ttiimmeess  Print the accumulated user and system times for  the  shell  and
              for processes run from the shell.  The return status is 0.

       ttrraapp [--llpp] [[_a_c_t_i_o_n] _s_i_g_s_p_e_c ...]
              The _a_c_t_i_o_n is a command that is read and executed when the shell
              receives signal(s) _s_i_g_s_p_e_c.  If _a_c_t_i_o_n is absent (and there is a
              single  _s_i_g_s_p_e_c)  or  --,  each  specified signal is reset to its
              original disposition (the value it  had  upon  entrance  to  the
              shell).   If  _a_c_t_i_o_n  is the null string the signal specified by
              each _s_i_g_s_p_e_c is ignored by the shell and by the commands it  in-
              vokes.

              If  no arguments are supplied, ttrraapp displays the actions associ-
              ated with each trapped signal as a set of ttrraapp commands that can
              be reused as shell input to restore the current signal  disposi-
              tions.   If  --pp  is  given, and _a_c_t_i_o_n is not present, then ttrraapp
              displays the actions associated with each _s_i_g_s_p_e_c  or,  if  none
              are supplied, for all trapped signals, as a set of ttrraapp commands
              that  can be reused as shell input to restore the current signal
              dispositions.  The --PP option  behaves  similarly,  but  displays
              only  the actions associated with each _s_i_g_s_p_e_c argument.  --PP re-
              quires at least one _s_i_g_s_p_e_c argument.  The --PP or --pp  options  to
              ttrraapp  may  be used in a subshell environment (e.g., command sub-
              stitution) and, as long as they are used before ttrraapp is used  to
              change  a  signal's handling, will display the state of its par-
              ent's traps.

              The --ll option causes ttrraapp to print a list of  signal  names  and
              their  corresponding  numbers.   Each _s_i_g_s_p_e_c is either a signal
              name defined in <_s_i_g_n_a_l_._h>, or a signal  number.   Signal  names
              are case insensitive and the SSIIGG prefix is optional.

              If  a _s_i_g_s_p_e_c is EEXXIITT (0) the command _a_c_t_i_o_n is executed on exit
              from the shell.  If a _s_i_g_s_p_e_c is DDEEBBUUGG, the  command  _a_c_t_i_o_n  is
              executed before every _s_i_m_p_l_e _c_o_m_m_a_n_d, _f_o_r command, _c_a_s_e command,
              _s_e_l_e_c_t  command,  (( arithmetic command, [[ conditional command,
              arithmetic _f_o_r command, and before the first command executes in
              a shell function (see SSHHEELLLL GGRRAAMMMMAARR above).  Refer  to  the  de-
              scription  of  the  eexxttddeebbuugg option to the sshhoopptt builtin for de-
              tails of its effect on the DDEEBBUUGG trap.  If a _s_i_g_s_p_e_c is  RREETTUURRNN,
              the  command  _a_c_t_i_o_n is executed each time a shell function or a
              script executed with the .. or ssoouurrccee builtins  finishes  execut-
              ing.

              If  a  _s_i_g_s_p_e_c is EERRRR, the command _a_c_t_i_o_n is executed whenever a
              pipeline (which may consist of a single simple command), a list,
              or a compound command returns a non-zero exit status, subject to
              the following conditions.  The EERRRR trap is not executed  if  the
              failed command is part of the command list immediately following
              a  wwhhiillee  or uunnttiill keyword, part of the test in an _i_f statement,
              part of a command executed in a &&&& or |||| list except the command
              following the final &&&& or ||||, any command in a pipeline but  the
              last,  or  if the command's return value is being inverted using
              !!.  These are the same conditions obeyed by the eerrrreexxiitt (--ee) op-
              tion.

              When the shell is not interactive, signals ignored upon entry to
              the shell cannot be trapped or reset.  Interactive shells permit
              trapping signals ignored on entry.  Trapped signals that are not
              being ignored are reset to their original values in  a  subshell
              or  subshell environment when one is created.  The return status
              is false if any _s_i_g_s_p_e_c is invalid; otherwise ttrraapp returns true.

       ttrruuee   Does nothing, returns a 0 status.

       ttyyppee [--aaffttppPP] _n_a_m_e [_n_a_m_e ...]
              With no options, indicate how each _n_a_m_e would be interpreted  if
              used as a command name.  If the --tt option is used, ttyyppee prints a
              string  which  is  one  of _a_l_i_a_s, _k_e_y_w_o_r_d, _f_u_n_c_t_i_o_n, _b_u_i_l_t_i_n, or
              _f_i_l_e if  _n_a_m_e  is  an  alias,  shell  reserved  word,  function,
              builtin,  or executable disk file, respectively.  If the _n_a_m_e is
              not found, then nothing is printed, and ttyyppee returns a  non-zero
              exit  status.  If the --pp option is used, ttyyppee either returns the
              name of the executable file that would  be  found  by  searching
              $$PPAATTHH  if  _n_a_m_e  were specified as a command name, or nothing if
              "type -t name" would not return _f_i_l_e.  The --PP  option  forces  a
              PPAATTHH  search for each _n_a_m_e, even if "type -t name" would not re-
              turn _f_i_l_e.  If a command is hashed, --pp and --PP print  the  hashed
              value,  which  is not necessarily the file that appears first in
              PPAATTHH.  If the --aa option is used, ttyyppee prints all of  the  places
              that  contain  a command named _n_a_m_e.  This includes aliases, re-
              served words, functions, and builtins, but the path  search  op-
              tions (--pp and --PP) can be supplied to restrict the output to exe-
              cutable  files.   ttyyppee does not consult the table of hashed com-
              mands when using --aa with --pp, and only performs a PPAATTHH search for
              _n_a_m_e.  The --ff option suppresses shell function lookup,  as  with
              the  ccoommmmaanndd builtin.  ttyyppee returns true if all of the arguments
              are found, false if any are not found.

       uulliimmiitt [--HHSS] --aa
       uulliimmiitt [--HHSS] [--bbccddeeffiikkllmmnnppqqrrssttuuvvxxPPRRTT [_l_i_m_i_t]]
              Provides control over the resources available to the  shell  and
              to  processes started by it, on systems that allow such control.
              The --HH and --SS options specify that the hard or soft limit is set
              for the given resource.  A hard limit cannot be increased  by  a
              non-root  user  once it is set; a soft limit may be increased up
              to the value of the hard limit.  If neither --HH nor --SS is  speci-
              fied, both the soft and hard limits are set.  The value of _l_i_m_i_t
              can be a number in the unit specified for the resource or one of
              the special values hhaarrdd, ssoofftt, or uunnlliimmiitteedd, which stand for the
              current  hard  limit,  the current soft limit, and no limit, re-
              spectively.  If _l_i_m_i_t is omitted, the current value of the  soft
              limit of the resource is printed, unless the --HH option is given.
              When  more  than  one  resource is specified, the limit name and
              unit, if appropriate, are printed before the value.   Other  op-
              tions are interpreted as follows:
              --aa     All current limits are reported; no limits are set
              --bb     The maximum socket buffer size
              --cc     The maximum size of core files created
              --dd     The maximum size of a process's data segment
              --ee     The maximum scheduling priority ("nice").
              --ff     The  maximum  size  of files written by the shell and its
                     children
              --ii     The maximum number of pending signals
              --kk     The maximum number of kqueues that may be allocated
              --ll     The maximum size that may be locked into memory
              --mm     The maximum resident set size (many systems do not  honor
                     this limit)
              --nn     The maximum number of open file descriptors (most systems
                     do not allow this value to be set)
              --pp     The pipe size in 512-byte blocks (this may not be set)
              --qq     The maximum number of bytes in POSIX message queues
              --rr     The maximum real-time scheduling priority
              --ss     The maximum stack size
              --tt     The maximum amount of cpu time in seconds
              --uu     The  maximum  number  of  processes available to a single
                     user
              --vv     The maximum amount of virtual  memory  available  to  the
                     shell and, on some systems, to its children
              --xx     The maximum number of file locks
              --PP     The maximum number of pseudoterminals
              --RR     The  maximum  time  a  real-time  process  can run before
                     blocking, in microseconds
              --TT     The maximum number of threads

              If _l_i_m_i_t is given, and the --aa option is not used, _l_i_m_i_t  is  the
              new  value  of  the  specified resource.  If no option is given,
              then --ff is assumed.  Values are in 1024-byte increments,  except
              for  --tt,  which is in seconds; --RR, which is in microseconds; --pp,
              which is in units of 512-byte blocks; --PP, --TT, --bb,  --kk,  --nn,  and
              --uu,  which  are unscaled values; and, when in posix mode, --cc and
              --ff, which are in 512-byte increments.  The return  status  is  0
              unless  an  invalid  option or argument is supplied, or an error
              occurs while setting a new limit.

       uummaasskk [--pp] [--SS] [_m_o_d_e]
              The user file-creation mask is set to _m_o_d_e.  If _m_o_d_e begins with
              a digit, it is interpreted as an octal number; otherwise  it  is
              interpreted  as a symbolic mode mask similar to that accepted by
              _c_h_m_o_d(1).  If _m_o_d_e is omitted, the current value of the mask  is
              printed.   The  --SS  option causes the mask to be printed in sym-
              bolic form; the default output is an octal number.   If  the  --pp
              option is supplied, and _m_o_d_e is omitted, the output is in a form
              that may be reused as input.  The return status is 0 if the mode
              was  successfully  changed  or if no _m_o_d_e argument was supplied,
              and false otherwise.

       uunnaalliiaass [-aa] [_n_a_m_e ...]
              Remove each _n_a_m_e from the list of defined  aliases.   If  --aa  is
              supplied,  all  alias definitions are removed.  The return value
              is true unless a supplied _n_a_m_e is not a defined alias.

       uunnsseett [-ffvv] [-nn] [_n_a_m_e ...]
              For each _n_a_m_e, remove the corresponding  variable  or  function.
              If the --vv option is given, each _n_a_m_e refers to a shell variable,
              and  that  variable  is removed.  Read-only variables may not be
              unset.  If --ff is specified, each _n_a_m_e refers to  a  shell  func-
              tion,  and the function definition is removed.  If the --nn option
              is supplied, and _n_a_m_e is a variable with the _n_a_m_e_r_e_f  attribute,
              _n_a_m_e  will  be unset rather than the variable it references.  --nn
              has no effect if the --ff option is supplied.  If no  options  are
              supplied,  each  _n_a_m_e refers to a variable; if there is no vari-
              able by that name, a function with that name, if any, is  unset.
              Each  unset variable or function is removed from the environment
              passed  to  subsequent  commands.   If  any   of   BBAASSHH__AALLIIAASSEESS,
              BBAASSHH__AARRGGVV00,  BBAASSHH__CCMMDDSS,  BBAASSHH__CCOOMMMMAANNDD,  BBAASSHH__SSUUBBSSHHEELLLL,  BBAASSHHPPIIDD,
              CCOOMMPP__WWOORRDDBBRREEAAKKSS, DDIIRRSSTTAACCKK,  EEPPOOCCHHRREEAALLTTIIMMEE,  EEPPOOCCHHSSEECCOONNDDSS,  FFUUNNCC--
              NNAAMMEE,  GGRROOUUPPSS,  HHIISSTTCCMMDD, LLIINNEENNOO, RRAANNDDOOMM, SSEECCOONNDDSS, or SSRRAANNDDOOMM are
              unset, they lose their special properties, even if they are sub-
              sequently reset.  The exit status is true unless a _n_a_m_e is read-
              only or may not be unset.

       wwaaiitt [--ffnn] [--pp _v_a_r_n_a_m_e] [_i_d ...]
              Wait for each specified child process and return its termination
              status.  Each _i_d may be a process ID or a job specification;  if
              a  job  spec  is given, all processes in that job's pipeline are
              waited for.  If _i_d is not given,  wwaaiitt  waits  for  all  running
              background  jobs  and the last-executed process substitution, if
              its process id is the same as $$!!, and the return status is zero.
              If the --nn option is supplied, wwaaiitt waits for a single  job  from
              the list of _i_ds or, if no _i_ds are supplied, any job, to complete
              and  returns its exit status.  If none of the supplied arguments
              is a child of the shell, or if no arguments are supplied and the
              shell has no unwaited-for children, the exit status is 127.   If
              the  --pp option is supplied, the process or job identifier of the
              job for which the exit status is returned  is  assigned  to  the
              variable  _v_a_r_n_a_m_e  named  by  the option argument.  The variable
              will be unset initially, before any assignment.  This is  useful
              only  when  the --nn option is supplied.  Supplying the --ff option,
              when job control is enabled, forces wwaaiitt to wait for _i_d to  ter-
              minate before returning its status, instead of returning when it
              changes  status.  If _i_d specifies a non-existent process or job,
              the return status is 127.  If wwaaiitt is interrupted by  a  signal,
              the  return  status will be greater than 128, as described under
              SSIIGGNNAALLSS above.  Otherwise, the return status is the exit  status
              of the last process or job waited for.

SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE
       Bash-4.0  introduced the concept of a _s_h_e_l_l _c_o_m_p_a_t_i_b_i_l_i_t_y _l_e_v_e_l, speci-
       fied as a set of options to the shopt builtin (ccoommppaatt3311, ccoommppaatt3322, ccoomm--
       ppaatt4400, ccoommppaatt4411, and so on).  There is only one  current  compatibility
       level -- each option is mutually exclusive.  The compatibility level is
       intended  to allow users to select behavior from previous versions that
       is incompatible with newer versions while they migrate scripts  to  use
       current  features  and  behavior. It's intended to be a temporary solu-
       tion.

       This section does not mention behavior that is standard for a  particu-
       lar  version  (e.g., setting ccoommppaatt3322 means that quoting the rhs of the
       regexp matching operator quotes special regexp characters in the  word,
       which is default behavior in bash-3.2 and subsequent versions).

       If  a  user enables, say, ccoommppaatt3322, it may affect the behavior of other
       compatibility levels up to  and  including  the  current  compatibility
       level.   The  idea  is  that each compatibility level controls behavior
       that changed in that version of bbaasshh, but that behavior may  have  been
       present  in  earlier versions.  For instance, the change to use locale-
       based comparisons with the [[[[ command came  in  bash-4.1,  and  earlier
       versions used ASCII-based comparisons, so enabling ccoommppaatt3322 will enable
       ASCII-based  comparisons  as  well.  That granularity may not be suffi-
       cient for all uses, and as a result users should  employ  compatibility
       levels  carefully.   Read the documentation for a particular feature to
       find out the current behavior.

       Bash-4.3 introduced a new shell variable: BBAASSHH__CCOOMMPPAATT.  The  value  as-
       signed to this variable (a decimal version number like 4.2, or an inte-
       ger  corresponding to the ccoommppaatt_N_N option, like 42) determines the com-
       patibility level.

       Starting with bash-4.4, bbaasshh has begun deprecating older  compatibility
       levels.   Eventually, the options will be removed in favor of BBAASSHH__CCOOMM--
       PPAATT.

       Bash-5.0 was the final version for which there will  be  an  individual
       shopt option for the previous version. Users should control the compat-
       ibility level with BBAASSHH__CCOOMMPPAATT.

       The  following  table describes the behavior changes controlled by each
       compatibility level setting.  The ccoommppaatt_N_N tag is used as shorthand for
       setting the compatibility level to _N_N using one of the following mecha-
       nisms.  For versions prior to bash-5.0, the compatibility level may  be
       set  using  the  corresponding ccoommppaatt_N_N shopt option.  For bash-4.3 and
       later versions, the BBAASSHH__CCOOMMPPAATT variable is preferred, and  it  is  re-
       quired for bash-5.1 and later versions.

       ccoommppaatt3311
              +o      quoting the rhs of the [[[[ command's regexp matching oper-
                     ator (=~) has no special effect

       ccoommppaatt3322
              +o      the  <<  and >> operators to the [[[[ command do not consider
                     the current locale when comparing strings; they use ASCII
                     ordering.

       ccoommppaatt4400
              +o      the << and >> operators to the [[[[ command do  not  consider
                     the current locale when comparing strings; they use ASCII
                     ordering.  BBaasshh versions prior to bash-4.1 use ASCII col-
                     lation  and _s_t_r_c_m_p(3); bash-4.1 and later use the current
                     locale's collation sequence and _s_t_r_c_o_l_l(3).

       ccoommppaatt4411
              +o      in _p_o_s_i_x mode, ttiimmee may be followed by options and  still
                     be recognized as a reserved word (this is POSIX interpre-
                     tation 267)
              +o      in _p_o_s_i_x mode, the parser requires that an even number of
                     single  quotes  occur  in  the  _w_o_r_d portion of a double-
                     quoted parameter expansion and treats them specially,  so
                     that  characters  within the single quotes are considered
                     quoted (this is POSIX interpretation 221)

       ccoommppaatt4422
              +o      the replacement string in double-quoted pattern substitu-
                     tion does not undergo quote removal, as it does  in  ver-
                     sions after bash-4.2
              +o      in  posix mode, single quotes are considered special when
                     expanding the _w_o_r_d portion of a  double-quoted  parameter
                     expansion  and  can  be  used to quote a closing brace or
                     other special character (this is part of POSIX  interpre-
                     tation  221);  in  later  versions, single quotes are not
                     special within double-quoted word expansions

       ccoommppaatt4433
              +o      the shell does not print a warning message if an  attempt
                     is  made  to use a quoted compound assignment as an argu-
                     ment to declare (e.g., declare  -a  foo='(1  2)').  Later
                     versions warn that this usage is deprecated
              +o      word  expansion  errors  are  considered non-fatal errors
                     that cause the current command to  fail,  even  in  posix
                     mode  (the  default behavior is to make them fatal errors
                     that cause the shell to exit)
              +o      when  executing  a  shell  function,   the   loop   state
                     (while/until/etc.)  is not reset, so bbrreeaakk or ccoonnttiinnuuee in
                     that function will break or continue loops in the calling
                     context.  Bash-4.4 and later reset the loop state to pre-
                     vent this

       ccoommppaatt4444
              +o      the shell sets  up  the  values  used  by  BBAASSHH__AARRGGVV  and
                     BBAASSHH__AARRGGCC  so  they  can expand to the shell's positional
                     parameters even if extended debugging mode is not enabled
              +o      a subshell inherits loops from  its  parent  context,  so
                     bbrreeaakk  or  ccoonnttiinnuuee  will  cause  the  subshell  to exit.
                     Bash-5.0 and later reset the loop state  to  prevent  the
                     exit
              +o      variable  assignments  preceding builtins like eexxppoorrtt and
                     rreeaaddoonnllyy that set attributes continue to affect variables
                     with the same name in the calling environment even if the
                     shell is not in posix mode

       ccoommppaatt5500
              +o      Bash-5.1 changed the way $$RRAANNDDOOMM is generated  to  intro-
                     duce slightly more randomness. If the shell compatibility
                     level  is  set  to  50 or lower, it reverts to the method
                     from bash-5.0 and previous versions, so seeding the  ran-
                     dom  number generator by assigning a value to RRAANNDDOOMM will
                     produce the same sequence as in bash-5.0
              +o      If the command hash table is empty, bash  versions  prior
                     to  bash-5.1 printed an informational message to that ef-
                     fect, even when producing output that can  be  reused  as
                     input.  Bash-5.1  suppresses that message when the --ll op-
                     tion is supplied.

       ccoommppaatt5511
              +o      The uunnsseett builtin treats attempts  to  unset  array  sub-
                     scripts  @@ and ** differently depending on whether the ar-
                     ray is indexed or associative, and  differently  than  in
                     previous versions.
              +o      arithmetic commands ( ((((...)))) ) and the expressions in an
                     arithmetic for statement can be expanded more than once
              +o      expressions  used as arguments to arithmetic operators in
                     the [[[[ conditional command can be expanded more than once
              +o      the expressions in substring  parameter  brace  expansion
                     can be expanded more than once
              +o      the expressions in the $$((((...)))) word expansion can be ex-
                     panded more than once
              +o      arithmetic  expressions  used as indexed array subscripts
                     can be expanded more than once
              +o      tteesstt --vv, when given an argument of AA[[@@]], where  AA  is  an
                     existing associative array, will return true if the array
                     has  any set elements.  Bash-5.2 will look for and report
                     on a key named @@.
              +o      the  ${_p_a_r_a_m_e_t_e_r[[::]]==_v_a_l_u_e}  word  expansion  will  return
                     _v_a_l_u_e,  before any variable-specific transformations have
                     been performed (e.g., converting to lowercase).  Bash-5.2
                     will return the final value assigned to the variable.
              +o      Parsing command substitutions will behave as if  extended
                     globbing (see the description of the sshhoopptt builtin above)
                     is  enabled,  so that parsing a command substitution con-
                     taining an extglob pattern (say, as part of a shell func-
                     tion) will not fail.  This assumes the intent is  to  en-
                     able  extglob before the command is executed and word ex-
                     pansions are performed.  It will fail at  word  expansion
                     time  if extglob hasn't been enabled by the time the com-
                     mand is executed.

       ccoommppaatt5522
              +o      The tteesstt builtin uses its historical algorithm  to  parse
                     parenthesized  subexpressions when given five or more ar-
                     guments.
              +o      If the --pp or --PP option is supplied to the  bbiinndd  builtin,
                     bbiinndd treats any arguments remaining after option process-
                     ing  as  bindable command names, and displays any key se-
                     quences bound to those commands, instead of treating  the
                     arguments as key sequences to bind.

RREESSTTRRIICCTTEEDD SSHHEELLLL
       If bbaasshh is started with the name rrbbaasshh, or the --rr option is supplied at
       invocation,  the  shell becomes restricted.  A restricted shell is used
       to set up an environment more controlled than the standard  shell.   It
       behaves  identically  to bbaasshh with the exception that the following are
       disallowed or not performed:

       +o      changing directories with ccdd

       +o      setting or unsetting the values of SSHHEELLLL, PPAATTHH,  HHIISSTTFFIILLEE,  EENNVV,
              or BBAASSHH__EENNVV

       +o      specifying command names containing //

       +o      specifying  a  filename  containing  a // as an argument to the ..
              builtin command

       +o      specifying a filename containing a slash as an argument  to  the
              hhiissttoorryy builtin command

       +o      specifying  a  filename containing a slash as an argument to the
              --pp option to the hhaasshh builtin command

       +o      importing function definitions from  the  shell  environment  at
              startup

       +o      parsing  the  value  of  SSHHEELLLLOOPPTTSS from the shell environment at
              startup

       +o      redirecting output using the >, >|, <>, >&, &>, and >>  redirec-
              tion operators

       +o      using the eexxeecc builtin command to replace the shell with another
              command

       +o      adding  or  deleting builtin commands with the --ff and --dd options
              to the eennaabbllee builtin command

       +o      using the  eennaabbllee  builtin  command  to  enable  disabled  shell
              builtins

       +o      specifying the --pp option to the ccoommmmaanndd builtin command

       +o      turning  off  restricted  mode  with  sseett  ++rr  or  sshhoopptt  --uu rree--
              ssttrriicctteedd__sshheellll.

       These restrictions are enforced after any startup files are read.

       When a command that is found to be a shell script is executed (see CCOOMM--
       MMAANNDD EEXXEECCUUTTIIOONN above), rrbbaasshh turns off any restrictions  in  the  shell
       spawned to execute the script.

SSEEEE AALLSSOO
       _B_a_s_h _R_e_f_e_r_e_n_c_e _M_a_n_u_a_l, Brian Fox and Chet Ramey
       _T_h_e _G_n_u _R_e_a_d_l_i_n_e _L_i_b_r_a_r_y, Brian Fox and Chet Ramey
       _T_h_e _G_n_u _H_i_s_t_o_r_y _L_i_b_r_a_r_y, Brian Fox and Chet Ramey
       _P_o_r_t_a_b_l_e _O_p_e_r_a_t_i_n_g _S_y_s_t_e_m _I_n_t_e_r_f_a_c_e _(_P_O_S_I_X_) _P_a_r_t _2_: _S_h_e_l_l _a_n_d _U_t_i_l_i_-
       _t_i_e_s, IEEE --
              http://pubs.opengroup.org/onlinepubs/9699919799/
       http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
       _s_h(1), _k_s_h(1), _c_s_h(1)
       _e_m_a_c_s(1), _v_i(1)
       _r_e_a_d_l_i_n_e(3)

FFIILLEESS
       _/_b_i_n_/_b_a_s_h
              The bbaasshh executable
       _/_e_t_c_/_p_r_o_f_i_l_e
              The systemwide initialization file, executed for login shells
       _~_/_._b_a_s_h___p_r_o_f_i_l_e
              The personal initialization file, executed for login shells
       _~_/_._b_a_s_h_r_c
              The individual per-interactive-shell startup file
       _~_/_._b_a_s_h___l_o_g_o_u_t
              The  individual  login shell cleanup file, executed when a login
              shell exits
       _~_/_._b_a_s_h___h_i_s_t_o_r_y
              The default value of HHIISSTTFFIILLEE, the file in which bash saves  the
              command history
       _~_/_._i_n_p_u_t_r_c
              Individual _r_e_a_d_l_i_n_e initialization file

AAUUTTHHOORRSS
       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet.ramey@case.edu

BBUUGG RREEPPOORRTTSS
       If you find a bug in bbaasshh, you should report it.  But first, you should
       make  sure  that  it really is a bug, and that it appears in the latest
       version  of  bbaasshh.   The  latest  version  is  always  available   from
       _f_t_p_:_/_/_f_t_p_._g_n_u_._o_r_g_/_p_u_b_/_g_n_u_/_b_a_s_h_/          and          _h_t_t_p_:_/_/_g_i_t_._s_a_v_a_n_-
       _n_a_h_._g_n_u_._o_r_g_/_c_g_i_t_/_b_a_s_h_._g_i_t_/_s_n_a_p_s_h_o_t_/_b_a_s_h_-_m_a_s_t_e_r_._t_a_r_._g_z.

       Once you have determined that a bug actually exists,  use  the  _b_a_s_h_b_u_g
       command  to submit a bug report.  If you have a fix, you are encouraged
       to mail that as well!  You may send suggestions and "philosophical" bug
       reports to _b_u_g_-_b_a_s_h_@_g_n_u_._o_r_g  or  post  them  to  the  Usenet  newsgroup
       ggnnuu..bbaasshh..bbuugg.

       ALL bug reports should include:

       The version number of bbaasshh
       The hardware and operating system
       The compiler used to compile
       A description of the bug behaviour
       A short script or "recipe" which exercises the bug

       _b_a_s_h_b_u_g  inserts  the first three items automatically into the template
       it provides for filing a bug report.

       Comments and bug reports concerning this manual page should be directed
       to _c_h_e_t_._r_a_m_e_y_@_c_a_s_e_._e_d_u.

BBUUGGSS
       It's too big and too slow.

       There are some subtle differences between bbaasshh and traditional versions
       of sshh, mostly because of the PPOOSSIIXX specification.

       Aliases are confusing in some uses.

       Shell builtin commands and functions are not stoppable/restartable.

       Compound commands and command sequences of the form "a ; b ; c" are not
       handled gracefully  when  process  suspension  is  attempted.   When  a
       process  is stopped, the shell immediately executes the next command in
       the sequence.  It suffices to place the sequence  of  commands  between
       parentheses  to  force  it  into  a subshell, which may be stopped as a
       unit, or to start the command in the background and  immediately  bring
       it into the foreground.

       Array variables may not (yet) be exported.

       There may be only one active coprocess at a time.

GNU Bash 5.3                     2024 June 12                          _B_A_S_H(1)
