BASH(1)                     General Commands Manual                    BASH(1)



NNAAMMEE
       bash - GNU Bourne-Again SHell

SSYYNNOOPPSSIISS
       bbaasshh [options] [command_string | file]

CCOOPPYYRRIIGGHHTT
       Bash is Copyright (C) 1989-2022 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).

       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  file-
                 names and arguments.  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 (por-
              table 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.  If bbaasshh is invoked  in  this
       fashion,  $$00 is set to the name of the file, and the positional parame-
       ters are set to the remaining arguments.  BBaasshh reads and executes  com-
       mands  from this file, then exits.  BBaasshh's exit status is the exit sta-
       tus of the last command executed in the script.  If no commands are ex-
       ecuted,  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 remote shell
       daemon, usually _r_s_h_d, or the secure shell daemon _s_s_h_d.  If bbaasshh  deter-
       mines  it  is being run 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 may be used to
       specify the format of the time information.

       Each command in a pipeline is executed in a _s_u_b_s_h_e_l_l, which is a  sepa-
       rate  process.   See CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT for a description of
       subshells and a subshell environment.  If the llaassttppiippee  option  is  en-
       abled 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 (the expansions that would occur if  the  words  were  en-
              closed in double quotes).  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 ev-
              ery  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.

              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.  The set of expanded words is printed on the standard er-
              ror,  each preceded by a number.  If the iinn _w_o_r_d is omitted, the
              positional parameters are printed (see PPAARRAAMMEETTEERRSS  below).   The
              PPSS33  prompt  is then displayed and a line read 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 displayed  again.
              If  EOF  is  read,  the command completes.  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 executed 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  copro-
       cess  always being named CCOOPPRROOCC, and it is simpler to use and more com-
       plete 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 SSHHEELLLLBUILTINCCOOMMMMAANNDDSS.

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 PPaarraamm--
       eetteerrss.   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  pa-
              rameter  expands  to  a  separate word.  In contexts where it is
              performed, 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  pa-
              rameter  separated  by  the  first  character of the IIFFSS special
              variable.  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  begin-
              ning  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, "$$@@" and $$@@ expand 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 pipeline.
       --      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.
       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.
       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
              $${{BBAASSHH__LLIINNEENNOO[[_$_i_-_1]]}} if referenced within  another  shell  func-
              tion).  Use LLIINNEENNOO to obtain the current line number.
       BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH
              A  colon-separated  list of directories in which the shell looks
              for dynamically loadable builtins specified by the  eennaabbllee  com-
              mand.
       BBAASSHH__RREEMMAATTCCHH
              An  array  variable  whose members are assigned by the ==~~ binary
              operator to the [[[[ conditional command.  The element with  index
              0  is  the portion of the string matching the entire regular ex-
              pression.  The element with index _n is the portion of the string
              matching the _nth parenthesized subexpression.
       BBAASSHH__SSOOUURRCCEE
              An  array  variable whose members are the source filenames where
              the corresponding shell function names  in  the  FFUUNNCCNNAAMMEE  array
              variable are defined.  The shell function $${{FFUUNNCCNNAAMMEE[[_$_i]]}} is de-
              fined  in  the   file   $${{BBAASSHH__SSOOUURRCCEE[[_$_i]]}}   and   called   from
              $${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}}.
       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__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_1).
              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 $${{CCOOMMPP__WWOORRDDSS}} of the word containing the current
              cursor position.  This variable is available only in shell func-
              tions  invoked  by  the  programmable completion facilities (see
              PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__KKEEYY
              The key (or final key of a key sequence) used to invoke the cur-
              rent completion function.
       CCOOMMPP__LLIINNEE
              The  current  command  line.  This variable is available only in
              shell functions and external commands invoked  by  the  program-
              mable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__PPOOIINNTT
              The  index of the current cursor position relative to the begin-
              ning of the current command.  If the current cursor position  is
              at the end of the current command, the value of this variable is
              equal to $${{##CCOOMMPP__LLIINNEE}}.  This  variable  is  available  only  in
              shell  functions  and  external commands invoked by the program-
              mable 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  program-
              mable 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 contain only a single command).
       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 /dev/urandom or  _a_r_c_4_r_a_n_d_o_m,  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.  The valid values corre-
              spond 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 compat-
              ibility 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 _s_e_t _-_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.   Bash 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.
       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).  The default value is _~_/_._b_a_s_h___h_i_s_t_o_r_y.   If  unset,
              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.  Each pattern is  an-
              chored  at the beginning of the line and must match the complete
              line (no implicit `**' is  appended).   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.  `&&' may be es-
              caped using a backslash; the backslash  is  removed  before  at-
              tempting  a  match.  The second and subsequent lines of a multi-
              line compound command are not tested, and are added to the  his-
              tory  regardless of the value of HHIISSTTIIGGNNOORREE.  The pattern match-
              ing 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><new-
              line>''.
       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/lo-
              cal/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 _s_e_t _-_o _p_o_s_i_x 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
              ``\\ss--\\vv\\$$ ''.
       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 braces 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 three places
              after  the  decimal  point may be specified; values of _p greater
              than 3 are changed to 3.  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,
              no timing information is displayed.  A trailing newline 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.   The  default  is
              `^^'.   The optional third character is the character which indi-
              cates that the remainder of the line is a comment when found  as
              the  first  character of a word, normally `##'.  The history com-
              ment 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 all the shell  expan-
       sions  described  below under EEXXPPAANNSSIIOONN.  When assigning to indexed ar-
       rays, if the optional brackets and subscript 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.

       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.   These
       subscripts  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 legal, 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.  There are seven kinds of expansion performed: _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, and _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n.

       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; and pathname  expan-
       sion.

       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.

       After these expansions are performed, quote characters present  in  the
       original  word  are  removed  unless  they  have been quoted themselves
       (_q_u_o_t_e _r_e_m_o_v_a_l).

       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.  Supplied integers may  be  prefixed
       with  _0  to force each term to have the same width.  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 expands to each character  lexico-
       graphically  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.

       Bash 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.  Bash 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 @@, an indexed array subscripted by @@ or **,
              or an associative array name, the results  differ  as  described
              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  @@, the result is _l_e_n_g_t_h positional parameters
              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.  It is an  expan-
              sion 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  op-
              eration 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 vari-
              able  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%%_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 pat-
              tern (the ``%%%%'' case) deleted.  If _p_a_r_a_m_e_t_e_r is  @@  or  **,  the
              pattern  removal operation is applied to each positional parame-
              ter 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 as-
                     sociative  arrays as a sequence of quoted key-value pairs
                     (see AArrrraayyss above).
              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 name.  There are two forms:

              $$((_c_o_m_m_a_n_d))
       or
              ``_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)).

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

       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, word splitting and
       pathname expansion are not performed 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 param-
       eter  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 default, then sequences of  <<ssppaaccee>>,  <<ttaabb>>,
       and  <<nneewwlliinnee>>  at the beginning and end of the results of the previous
       expansions are ignored, and any sequence 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  white-
       space  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.

       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'' becomes
       -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 ex-
       plicitly, unless the shell option ddoottgglloobb is set.  In  order  to  match
       the filenames ````..''''  and ````....'''', the pattern must begin with ``.'' (for
       example, ``.?''), even if ddoottgglloobb is set.  If  the  gglloobbsskkiippddoottss  shell
       option  is enabled, the filenames ````..''''  and ````....''''  are never matched,
       even if the pattern begins with a ````..''''.  When not matching  pathnames,
       the  ````..''''   character is not treated specially.  When matching a path-
       name, 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 GGLLOOBBIIGG--
       NNOORREE  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 ````..''''  will match.  To get the old behavior
       of ignoring filenames beginning with a ````..'''', make ````..**''''  one  of  the
       patterns in GGLLOOBBIIGGNNOORREE.  The ddoottgglloobb option is disabled when GGLLOOBBIIGGNNOORREE
       is unset.  The pattern matching honors the setting of the eexxttgglloobb shell
       option.

       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 is determined by the current  locale
                     and  the  values  of the LLCC__CCOOLLLLAATTEE or LLCC__AALLLL shell vari-
                     ables, if set.  To obtain the traditional  interpretation
                     of  range  expressions,  where  [[aa--dd]]  is  equivalent  to
                     [[aabbccdd]], set value of the LLCC__AALLLL shell variable to  CC,  or
                     enable  the  gglloobbaasscciiiirraannggeess  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

       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 ``.'' unless 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 redirect-
       ion 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 re-
       direction 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 re-
       direction 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 a line containing only _d_e_l_i_m_i_t_e_r (with no trailing
       blanks)  is seen.  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 removal on _w_o_r_d,
       and the lines in the here-document are not expanded.  If  _w_o_r_d  is  un-
       quoted,  all  lines of the here-document are subjected to parameter ex-
       pansion, command substitution, and arithmetic expansion, the  character
       sequence \\<<nneewwlliinnee>> is ignored, and \\ must be used to quote the charac-
       ters \\, $$, 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  re-
       direction  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 when it is used as
       the first word of a simple command.  The  shell  maintains  a  list  of
       aliases  that  may  be set and unset with the aalliiaass and uunnaalliiaass builtin
       commands (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  The first  word  of  each
       simple  command, if unquoted, is checked to see if it has an alias.  If
       so, that word is replaced by the text of the alias.  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  command
       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.  Ordinarily, variables and their values are shared between the
       function and its caller.  If a variable is declared  llooccaall,  the  vari-
       able's  visible  scope  is restricted to that function and its children
       (including the functions it calls).  Local variables "shadow" variables
       with  the same name declared at previous 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 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 previ-
       ous scope, any instance of a variable with  that  name  that  had  been
       shadowed will become visible.

       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 [[[[, the << and >> operators sort  lexicographically  using
       the current locale.  The tteesstt command sorts using ASCII ordering.

       --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).
       --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 following actions are
       taken.

       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.

       Subshells spawned to execute command substitutions inherit the value of
       the --ee option from the parent shell.  When  not  in  _p_o_s_i_x  _m_o_d_e,  bbaasshh
       clears the --ee option in such subshells.

       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  pro-
       cesses.  Executed commands inherit the environment.  The eexxppoorrtt and ddee--
       ccllaarree --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 pro-
       cesses 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
       driver 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 stty
       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 ````ffgg %%11'''', bringing job 1 from the  background  into  the
       foreground.   Similarly,  ````%%11  &&''''  resumes  job  1 in the background,
       equivalent to ````bbgg %%11''''.

       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  a variable value is read, empty or null values, "on" (case-insen-
       sitive), 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, readline attempts to bind the control characters
              treated specially by the kernel's terminal driver to their read-
              line equivalents.
       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.
       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 will configure the terminal in a way
              that will enable it to insert each paste into the editing buffer
              as a single string of characters, instead of treating each char-
              acter as if it had been read from the keyboard.  This  can  pre-
              vent  pasted  characters  from being interpreted as editing com-
              mands.
       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.
       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, causes readline to match files
              whose names begin with a  `.'  (hidden  files)  when  performing
              filename  completion.   If  set  to OOffff, the leading `.' must be
              supplied by the user 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.
       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.
       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
              characters 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.

              aapppplliiccaattiioonn
                     The aapppplliiccaattiioonn 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, any remembered search string is used.

       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.
       eenndd--ooff--lliinnee ((CC--ee))
              Move to the end of the line.
       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--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.
       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.
       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 as the shell does.  This performs alias and his-
              tory expansion as well as all of the shell word expansions.  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
              ``stty''.  If this character is read when there are  no  charac-
              ters  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.

   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 count searches for previous occur-
              rences.
       cchhaarraacctteerr--sseeaarrcchh--bbaacckkwwaarrdd ((MM--CC--]]))
              A character is read and point is moved to  the  previous  occur-
              rence  of  that character.  A negative count searches for subse-
              quent 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 program-
       mable 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  if the history file is un-
       writable, the history is not saved.  If the HHIISSTTTTIIMMEEFFOORRMMAATT variable  is
       set,  time stamps are written to the history file, marked with the his-
       tory comment character, so they may be preserved across shell sessions.
       This  uses the history comment character to distinguish timestamps from
       other history lines.  After saving the history,  the  history  file  is
       truncated  to contain no more than HHIISSTTFFIILLEESSIIZZEE lines.  If HHIISSTTFFIILLEESSIIZZEE
       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 may be set 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.  Various _m_o_d_i_f_i_e_r_s are  avail-
       able  to  manipulate the selected words.  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.  His-
       tory expansions are introduced by the appearance of the history  expan-
       sion  character,  which is !! by default.  Only backslash (\\) and single
       quotes can quote the history expansion character, but the  history  ex-
       pansion  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 ==.  If the eexxttgglloobb shell  option  is
       enabled, (( will also inhibit expansion.

       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.   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.

        ..  _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
       ssoouurrccee _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
              Read and execute commands from _f_i_l_e_n_a_m_e in the current shell en-
              vironment  and  return  the exit status of the last command exe-
              cuted from _f_i_l_e_n_a_m_e.  If _f_i_l_e_n_a_m_e  does  not  contain  a  slash,
              filenames  in  PPAATTHH  are  used  to find the directory containing
              _f_i_l_e_n_a_m_e, but _f_i_l_e_n_a_m_e does not need to be executable.  The file
              searched  for  in PPAATTHH need not be executable.  When bbaasshh is not
              in _p_o_s_i_x _m_o_d_e, the current directory is searched if no  file  is
              found  in  PPAATTHH.   If the ssoouurrcceeppaatthh option to the sshhoopptt builtin
              command is turned off, the PPAATTHH is not searched.  If  any  _a_r_g_u_-
              _m_e_n_t_s  are  supplied, they become the positional parameters when
              _f_i_l_e_n_a_m_e is executed.  Otherwise the positional  parameters  are
              unchanged.   If the --TT option 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 exe-
              cutes.  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] [--llppssvvPPSSVVXX]
       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] _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'.   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.
              --PP     List current rreeaaddlliinnee function names and bindings.
              --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.  When _s_h_e_l_l_-_c_o_m_m_a_n_d is executed,  the  shell  sets
                     the  RREEAADDLLIINNEE__LLIINNEE  variable to the contents of the rreeaadd--
                     lliinnee 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__AARRGGUUMMEENNTT variable.  If there was no argu-
                     ment,  that variable is not set.  If the executed command
                     changes  the  value  of  any  of   RREEAADDLLIINNEE__LLIINNEE,   RREEAADD--
                     LLIINNEE__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:  each directory name in CCDDPPAATTHH is searched for _d_i_r.  Alter-
              native directory names in CCDDPPAATTHH are separated by a  colon  (:).
              A  null  directory name in CCDDPPAATTHH is the same as the current di-
              rectory, 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  pro-
              cessed  by  removing the immediately previous pathname component
              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 [_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 exception of --pp and --rr, and write the matches
              to the standard output.  When using the --FF or  --CC  options,  the
              various  shell  variables set by the programmable completion fa-
              cilities, 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 are supplied, existing
              completion specifications are printed in a way that allows  them
              to be reused as input.  The --rr option removes a completion spec-
              ification for each _n_a_m_e, or, if no _n_a_m_es are supplied, all  com-
              pletion specifications.  The --DD option indicates that other sup-
              plied options and actions should apply to the  ``default''  com-
              mand  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 delimiter
              such as ;; or ||, which is usually command  name  completion.   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 ignored; 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 PPrrooggrraamm--
              mmaabbllee 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.
                      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.
              --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 or --rr is supplied without a  _n_a_m_e  argu-
              ment,  an  attempt  is made to remove a completion specification
              for a _n_a_m_e for which no specification exists, or an error 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 last enclosing loop (the ``top-level''  loop)
              is  resumed.  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 at-
              tributes and values of all shell variables.  The --ff option  will
              restrict 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 attri-
              bute 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 expands these es-
              cape characters by default.  eecchhoo does not interpret ---- to  mean
              the  end  of  options.  eecchhoo interprets the following escape se-
              quences:
              \\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.
              Bash 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.   The  default  is  system-dependent.   The --dd option will
              delete a builtin previously loaded with --ff.  If  no  _n_a_m_e  argu-
              ments  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  re-
              stricted  to the POSIX _s_p_e_c_i_a_l builtins.  If no options are sup-
              plied 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.

       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 an invalid option is seen, ggeettooppttss places ? into _n_a_m_e and, if
              not  silent,  prints  an  error  message  and unsets OOPPTTAARRGG.  If
              ggeettooppttss is silent, the option character found is placed  in  OOPP--
              TTAARRGG and no diagnostic message is printed.

              If  a required argument is not found, and ggeettooppttss is not silent,
              a question mark (??) is placed in _n_a_m_e, OOPPTTAARRGG is  unset,  and  a
              diagnostic  message  is  printed.   If ggeettooppttss is silent, then a
              colon (::) is placed in _n_a_m_e and OOPPTTAARRGG  is  set  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, no path search is performed, and _f_i_l_e_n_a_m_e
              is  used  as  the  full  filename of the command.  The --rr option
              causes the shell to forget all remembered locations.  The --dd op-
              tion  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 for-
              mat that may be reused as input.  If no arguments are given,  or
              if only --ll is supplied, information about remembered commands is
              printed.  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.  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 are
              restored to their original values  when  the  function  returns.
              The restore is effected as if a series of sseett commands were exe-
              cuted to restore the values that were in place before the  func-
              tion.   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(1) format specifications, pprriinnttff
              interprets the following extensions:
              %%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     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 directives all use the field width and preci-
              sion arguments from the format specification and write that many
              bytes from (or use that wide a field for) the expanded argument,
              which usually contains more characters than the original.

              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 on failure.

       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 [--eerrss] [--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, rreeaaddlliinnee
                     (see  RREEAADDLLIINNEE  above) is used to obtain the line.  Read-
                     line uses the current (or default, if  line  editing  was
                     not  previously  active) editing settings, but uses Read-
                     line's default filename completion.
              --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.

              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 ...]
              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  ``IG-
                              NOREEOF=10''  had been executed (see SShheellll VVaarrii--
                              aabblleess 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, the values of the
                      current  options are printed.  If ++oo is supplied with no
                      _o_p_t_i_o_n_-_n_a_m_e, a series of sseett commands  to  recreate  the
                      current  option  settings  is  displayed 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.
              --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 $$##, the positional param-
              eters  are  not changed.  The return status is greater than zero
              if _n is greater than $$## 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:

              aassssoocc__eexxppaanndd__oonnccee
                      If  set, the shell suppresses multiple evaluation of as-
                      sociative array subscripts during arithmetic  expression
                      evaluation,  while  executing  builtins that can perform
                      variable assignments, and while executing builtins  that
                      perform array dereferencing.
              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 buf-
                      fer.  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
                      ddoottgglloobb 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,  the
                      message  ``The  mail in _m_a_i_l_f_i_l_e has been read'' is dis-
                      played.

              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, bbaasshh allows patterns which match no  files  (see
                      PPaatthhnnaammee  EExxppaannssiioonn  above)  to expand to a null string,
                      rather than 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.  This option 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 RREE--
                      DDIIRREECCTTIIOONN above) instead of leaving them open  when  the
                      command completes.

              xxppgg__eecchhoo
                      If  set,  the  eecchhoo builtin expands backslash-escape se-
                      quences by default.

       ssuussppeenndd [--ff]
              Suspend the execution of this shell until it receives a  SSIIGGCCOONNTT
              signal.  A login shell cannot be suspended; the --ff option can be
              used to override this and force the suspension.  The return sta-
              tus  is  0  unless the shell is a login shell and --ff is not sup-
              plied, or if job control is not enabled.

       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 op-
              erand 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  used  with  tteesstt  or [[, the << and >> operators sort lexico-
              graphically 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_r_g] _s_i_g_s_p_e_c ...]
              The  command  _a_r_g  is to be read and executed when the shell re-
              ceives signal(s) _s_i_g_s_p_e_c.  If _a_r_g is absent (and there is a sin-
              gle  _s_i_g_s_p_e_c) or --, each specified signal is reset to its origi-
              nal disposition (the value it had upon entrance to  the  shell).
              If  _a_r_g  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 invokes.  If  _a_r_g
              is  not present and --pp has been supplied, then the trap commands
              associated with each _s_i_g_s_p_e_c are displayed.  If no arguments are
              supplied  or  if  only --pp is given, ttrraapp prints the list of com-
              mands associated with each signal.  The  --ll  option  causes  the
              shell  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_r_g  is  executed  on  exit
              from  the shell.  If a _s_i_g_s_p_e_c is DDEEBBUUGG, the command _a_r_g is exe-
              cuted 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,  every  arithmetic  _f_o_r command, and before the
              first command executes in a shell function  (see  SSHHEELLLL  GGRRAAMMMMAARR
              above).   Refer to the description of the eexxttddeebbuugg option to the
              sshhoopptt builtin for details of its effect on the DDEEBBUUGG trap.  If a
              _s_i_g_s_p_e_c is RREETTUURRNN, the command _a_r_g is executed each time a shell
              function or a script executed with the .. or ssoouurrccee builtins fin-
              ishes executing.

              If  a  _s_i_g_s_p_e_c  is  EERRRR,  the command _a_r_g 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.

              Signals ignored upon entry to the shell cannot be trapped or re-
              set.  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.

       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 disk file, respectively.  If the _n_a_m_e is not found,
              then nothing is printed, and an exit  status  of  false  is  re-
              turned.   If the --pp option is used, ttyyppee either returns the name
              of the disk file that would be executed if _n_a_m_e  were  specified
              as  a command name, or nothing if ``type -t name'' would not re-
              turn _f_i_l_e.  The --PP option forces a PPAATTHH search  for  each  _n_a_m_e,
              even if ``type -t name'' would not return _f_i_l_e.  If a command is
              hashed, --pp and --PP print the hashed value, which is not necessar-
              ily  the  file  that appears first in PPAATTHH.  If the --aa option is
              used, ttyyppee prints all of the places that contain  an  executable
              named _n_a_m_e.  This includes aliases and functions, if and only if
              the --pp option is not also used.  The table of hashed commands is
              not  consulted  when  using  --aa.  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.  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,
       ccoommppaatt4400,  ccoommppaatt4411, and so on).  There is only one current compatibil-
       ity level -- each option  is  mutually  exclusive.   The  compatibility
       level  is intended to allow users to select behavior from previous ver-
       sions that is incompatible  with  newer  versions  while  they  migrate
       scripts  to  use  current  features and behavior. It's intended to be a
       temporary solution.

       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 above).

       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, Bash has begun deprecating older  compatibility
       levels.   Eventually, the options will be removed in favor of BBAASSHH__CCOOMM--
       PPAATT.

       Bash-5.0 is the final version for which there  will  be  an  individual
       shopt  option for the previous version. Users should use BBAASSHH__CCOOMMPPAATT on
       bash-5.0 and later versions.

       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      interrupting  a  command  list such as "a ; b ; c" causes
                     the execution  of  the  next  command  in  the  list  (in
                     bash-4.0  and later versions, the shell acts as if it re-
                     ceived the interrupt, so interrupting one  command  in  a
                     list aborts the execution of the entire list)

       ccoommppaatt4400
              +o      the  <<  and >> operators to the [[[[ command do not consider
                     the current locale when comparing strings; they use ASCII
                     ordering.  Bash 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 (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.

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 >> redirect-
              ion 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!  Suggestions and `philosophical' bug reports  may
       be  mailed  to  _b_u_g_-_b_a_s_h_@_g_n_u_._o_r_g  or  posted  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.

       Array variables may not (yet) be exported.

       There may be only one active coprocess at a time.



GNU Bash 5.2                   2022 February 10                        BASH(1)
