BASH(1)                     General Commands Manual                    BASH(1)



NNAAMMEE
       bash - GNU Bourne-Again SHell

SSYYNNOOPPSSIISS
       bbaasshh [options] [command_string | file]

CCOOPPYYRRIIGGHHTT
       Bash is Copyright (C) 1989-2018 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
       options 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
                 assigned  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 mes-
                 sages.
       --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
       options  must  appear  on  the command line before the single-character
       options 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
              IINNVVOOCCAATTIIOONN 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
              below).

       ----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
              default 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
       executed, the exit status is 0.  An attempt is first made to  open  the
       file in the current directory, and, if no file is found, then the shell
       searches the directories in PPAATTHH for the script.

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

       An  _i_n_t_e_r_a_c_t_i_v_e  shell  is  one  started  without  non-option arguments
       (unless --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
       example, 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
       behavior  of  historical  versions  of sshh as closely as possible, while
       conforming to the POSIX standard as well.  When invoked as an  interac-
       tive  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
       inhibit 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
       attempt 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
       appear  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 simple command (see SSHHEELLLL GGRRAAMMMMAARR below) or  the  third
       word of a ccaassee or ffoorr command:

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

SSHHEELLLL GGRRAAMMMMAARR
   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
       arguments 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 [ [|||||&&] _c_o_m_m_a_n_d_2 ... ]

       The standard output of _c_o_m_m_a_n_d 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 command (see RREEDDIIRREECCTTIIOONN below).  If ||&& is used,
       _c_o_m_m_a_n_d'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  the
       command.

       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 as a separate process (i.e.,  in
       a  subshell).  See CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT for a description of a
       subshell environment.  If the llaassttppiippee  option  is  enabled  using  the
       sshhoopptt builtin (see the description of sshhoopptt below), the last element of
       a pipeline may be run by the shell process.

   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.   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 executed.

       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 environment (see CCOOMMMMAANNDD EEXXEECCUU--
              TTIIOONN EENNVVIIRROONNMMEENNTT below).  Variable assignments and builtin  com-
              mands  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
              below  under AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN.  If the value of the expres-
              sion is non-zero, the return status is 0; otherwise  the  return
              status is 1.  This is exactly equivalent to lleett ""_e_x_p_r_e_s_s_i_o_n"".

       [[[[ _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.
              Word splitting and pathname expansion are not performed  on  the
              words  between  the  [[[[  and  ]]]]; tilde expansion, parameter and
              variable expansion, arithmetic expansion, command  substitution,
              process  substitution,  and quote removal are performed.  Condi-
              tional 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
              expression and matched accordingly (as 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.  Any part of the pattern may be
              quoted to force the quoted portion to be matched  as  a  string.
              Bracket expressions in regular expressions must be treated care-
              fully, since  normal  quoting  characters  lose  their  meanings
              between brackets.  If the pattern is stored in a shell variable,
              quoting the variable expansion forces the entire pattern  to  be
              matched as a string.  Substrings matched by parenthesized subex-
              pressions within the regular expression are saved in  the  array
              variable BBAASSHH__RREEMMAATTCCHH.  The element of BBAASSHH__RREEMMAATTCCHH with index 0
              is the portion of the string matching the entire regular expres-
              sion.   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
              parameter 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
              error,  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 stan-
              dard input.  If the line consists of a number  corresponding  to
              one  of  the  displayed  words, then the value of _n_a_m_e is set to
              that word.  If the line is empty, the words and prompt are  dis-
              played again.  If EOF is read, the 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,  and  process substitution.  If the nnooccaasseemmaattcchh shell
              option is enabled, the match is performed without regard to  the
              case  of alphabetic characters.  When a match is found, the cor-
              responding _l_i_s_t is executed.  If the ;;;;  operator  is  used,  no
              subsequent  matches are attempted after the first pattern match.
              Using ;;&& in place of ;;;; causes execution to  continue  with  the
              _l_i_s_t  associated  with  the  next set of patterns.  Using ;;;;&& in
              place of ;;;; causes the shell to test the next  pattern  list  in
              the statement, if any, and execute any associated _l_i_s_t on a suc-
              cessful match.  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,
              except  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 exe-
              cuted.

   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 format 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.  If  _N_A_M_E  is  not  supplied,  the
       default name is CCOOPPRROOCC.  _N_A_M_E must not be supplied if _c_o_m_m_a_n_d is a _s_i_m_-
       _p_l_e _c_o_m_m_a_n_d (see above); otherwise, it is interpreted as the first word
       of  the simple command.  When the coprocess is executed, the shell cre-
       ates 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  descriptor  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 assigned 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 available 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:

       _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 _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 _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,  with
              one  exception:  If  the ffuunnccttiioonn reserved word is used, but the
              parentheses are not supplied, the  braces  are  required.   _c_o_m_-
              _p_o_u_n_d_-_c_o_m_m_a_n_d is executed whenever _n_a_m_e is specified as the name
              of a simple command.  When in _p_o_s_i_x _m_o_d_e, _n_a_m_e 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.  Any redirections
              (see RREEDDIIRREECCTTIIOONN below) specified 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 exe-
              cuted, 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
       itself  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).

       Words of the form $$'_s_t_r_i_n_g' are treated specially.  The word expands to
       _s_t_r_i_n_g, with backslash-escaped characters replaced as specified by  the
       ANSI  C  standard.  Backslash escape sequences, if present, are decoded
       as follows:
              \\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.   If  the
       current  locale  is  CC  or  PPOOSSIIXX,  the dollar sign is ignored.  If the
       string is translated and replaced, the replacement is double-quoted.

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 is not
       performed, with the exception of ""$$@@"" as explained below under  SSppeecciiaall
       PPaarraammeetteerrss.   Pathname  expansion  is not performed.  Assignment state-
       ments may also appear 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
       _i_n_t_e_g_e_r  attribute  has  been  set, _v_a_l_u_e is evaluated as an arithmetic
       expression and added to the variable's current  value,  which  is  also
       evaluated.   When  +=  is  applied  to an array variable using compound
       assignment (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
       applied 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
       attributes 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,
       assignments, 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
              parameter 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
              parameter separated by the first character of  the  IIFFSS  special
              variable.   That  is, "$$**" is equivalent to "$$11_c$$22_c......", where _c
              is the first character of the value of the IIFFSS variable.  If IIFFSS
              is  unset,  the  parameters  are separated by spaces.  If IIFFSS is
              null, the parameters are joined without intervening separators.
       @@      Expands to the positional parameters,  starting  from  one.   In
              contexts  where  word  splitting is performed, this expands each
              positional parameter to a separate word; if  not  within  double
              quotes,  these words are subject to word splitting.  In contexts
              where word splitting is not performed, this expands to a  single
              word  with each positional parameter separated by a space.  When
              the  expansion  occurs  within  double  quotes,  each  parameter
              expands to a separate word.  That is, "$$@@" 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
              itself (such as the --ii option).
       $$      Expands to the process ID of the shell.  In a  ()  subshell,  it
              expands  to  the  process  ID of the current shell, not the sub-
              shell.
       !!      Expands to the process ID of the job most recently  placed  into
              the  background,  whether executed as an asynchronous command or
              using the bbgg builtin (see JJOOBB CCOONNTTRROOLL below).
       00      Expands to the name of the shell or shell script.  This  is  set
              at shell initialization.  If bbaasshh is invoked with a file of com-
              mands, $$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.
       __      At shell startup, set to the absolute pathname  used  to  invoke
              the  shell or shell script being executed as passed in the envi-
              ronment or argument list.  Subsequently,  expands  to  the  last
              argument  to  the  previous simple command executed in the fore-
              ground, 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.

   SShheellll VVaarriiaabblleess
       The following variables are set by the shell:

       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
              option 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
              below).  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 $$00.  If BBAASSHH__AARRGGVV00 is unset, it
              loses its special properties, even if it is subsequently reset.
       BBAASSHH__CCMMDDSS
              An associative array variable whose members  correspond  to  the
              internal  hash  table  of  commands  as  maintained  by the hhaasshh
              builtin.  Elements added to this array appear in the hash table;
              however,  unsetting array elements currently does not cause com-
              mand names to be removed from the hash table.  If  BBAASSHH__CCMMDDSS  is
              unset,  it  loses  its  special properties, even if it is subse-
              quently reset.
       BBAASSHH__CCOOMMMMAANNDD
              The command currently being executed or about  to  be  executed,
              unless the shell is executing a command as the result of a trap,
              in which case it is the command executing at  the  time  of  the
              trap.
       BBAASSHH__EEXXEECCUUTTIIOONN__SSTTRRIINNGG
              The command argument to the --cc invocation option.
       BBAASSHH__LLIINNEENNOO
              An  array  variable whose members are the line numbers in source
              files where each corresponding member of FFUUNNCCNNAAMMEE  was  invoked.
              $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}}  is  the  line  number  in  the  source  file
              ($${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}})  where  $${{FFUUNNCCNNAAMMEE[[_$_i]]}}  was  called  (or
              $${{BBAASSHH__LLIINNEENNOO[[_$_i_-_1]]}}  if  referenced  within another shell func-
              tion).  Use LLIINNEENNOO to obtain the current line number.
       BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH
              A colon-separated list of directories in which the  shell  looks
              for  dynamically  loadable builtins specified by the eennaabbllee com-
              mand.
       BBAASSHH__RREEMMAATTCCHH
              An array variable whose members are assigned by  the  ==~~  binary
              operator  to the [[[[ conditional command.  The element with index
              0 is the portion of  the  string  matching  the  entire  regular
              expression.   The  element  with  index  _n is the portion of the
              string matching the _nth parenthesized subexpression.  This vari-
              able is read-only.
       BBAASSHH__SSOOUURRCCEE
              An  array  variable whose members are the source filenames where
              the corresponding shell function names  in  the  FFUUNNCCNNAAMMEE  array
              variable  are  defined.   The  shell function $${{FFUUNNCCNNAAMMEE[[_$_i]]}} is
              defined  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.
       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
              described 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
              unset,  it  loses  its  special properties, even if it is subse-
              quently 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
              reset.

              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
              instance,   $${{FFUUNNCCNNAAMMEE[[_$_i]]}}   was   called   from    the    file
              $${{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.   If HHIISSTTCCMMDD is unset, 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, a random integer between
              0 and 32767 is generated.  The sequence of random numbers may be
              initialized by assigning a value to RRAANNDDOOMM.  If RRAANNDDOOMM is unset,
              it loses its special properties,  even  if  it  is  subsequently
              reset.
       RREEAADDLLIINNEE__LLIINNEE
              The contents of the rreeaaddlliinnee line buffer, for use with "bind -x"
              (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       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, the  number  of  seconds
              since  shell  invocation is returned.  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.
              If SSEECCOONNDDSS is unset, it loses its special properties, even if it
              is subsequently 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.
       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
       assigns 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
              the description of the sshhoopptt builtin below under  SSHHEELLLL  BBUUIILLTTIINN
              CCOOMMMMAANNDDSS  for  a description of the various compatibility levels
              and their effects.  The value may be  a  decimal  number  (e.g.,
              4.2)  or an integer (e.g., 42) corresponding to the desired com-
              patibility 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 compatibility levels correspond to
              the  compatibility  options  accepted  by  the   sshhoopptt   builtin
              described below (for example, ccoommppaatt4422 means that 4.2 and 42 are
              valid values).  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
              enabled  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
              directories 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
              array 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    Similar  to  BBAASSHH__EENNVV;  used  when the 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
              anchored at the beginning of the line and must  match  the  com-
              plete  line  (no  implicit  `**'  is  appended).  Each pattern is
              tested against the line after the checks specified  by  HHIISSTTCCOONN--
              TTRROOLL  are  applied.   In  addition  to  the normal shell pattern
              matching characters, `&&' matches the previous history line.  `&&'
              may  be  escaped  using  a  backslash;  the backslash is removed
              before attempting a match.  The second and subsequent lines of a
              multi-line compound command are not tested, and are added to the
              history regardless of the  value  of  HHIISSTTIIGGNNOORREE.   The  pattern
              matching honors the setting of the eexxttgglloobb shell option.
       HHIISSTTSSIIZZEE
              The  number  of commands to remember in the command history (see
              HHIISSTTOORRYY below).  If the value is 0, commands are  not  saved  in
              the history list.  Numeric values less than zero result in every
              command being saved on the history list  (there  is  no  limit).
              The  shell  sets  the  default  value  to  500 after reading any
              startup files.
       HHIISSTTTTIIMMEEFFOORRMMAATT
              If this variable is set and not null, its value  is  used  as  a
              format string for _s_t_r_f_t_i_m_e(3) to print the time stamp associated
              with each history entry displayed by the  hhiissttoorryy  builtin.   If
              this  variable  is  set,  time stamps are written to the history
              file so they may be preserved across shell sessions.  This  uses
              the  history  comment  character  to distinguish timestamps from
              other history lines.
       HHOOMMEE   The home directory of the current user; the default argument for
              the ccdd builtin command.  The value of this variable is also used
              when performing tilde expansion.
       HHOOSSTTFFIILLEE
              Contains the name of a file in the  same  format  as  _/_e_t_c_/_h_o_s_t_s
              that should be read when the shell needs to complete a hostname.
              The list of possible hostname completions may be  changed  while
              the  shell  is  running;  the  next  time hostname completion is
              attempted 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
              after  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
              default 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
              sequences 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 $$.
       LLCC__NNUUMMEERRIICC
              This  variable  determines  the  locale category used for number
              formatting.
       LLCC__TTIIMMEE
              This variable determines the locale category used for  data  and
              time formatting.
       LLIINNEESS  Used  by  the  sseelleecctt  compound  command to determine the column
              length for printing selection lists.  Automatically set  if  the
              cchheecckkwwiinnssiizzee  option  is enabled or in an interactive shell upon
              receipt of a SSIIGGWWIINNCCHH.
       MMAAIILL   If this parameter is set to a file or  directory  name  and  the
              MMAAIILLPPAATTHH  variable  is  not  set,  bbaasshh  informs the user of the
              arrival of mail in the specified file or  Maildir-format  direc-
              tory.
       MMAAIILLCCHHEECCKK
              Specifies  how  often  (in  seconds)  bbaasshh checks for mail.  The
              default is 60 seconds.  When it is time to check for  mail,  the
              shell  does  so  before  displaying the primary prompt.  If this
              variable is unset, or set to  a  value  that  is  not  a  number
              greater than or equal to zero, the shell disables mail checking.
       MMAAIILLPPAATTHH
              A colon-separated list of filenames to be checked for mail.  The
              message to be printed when mail arrives in a particular file may
              be  specified by separating the filename from the message with a
              `?'.  When used in the text of the message, $$__  expands  to  the
              name of the current mailfile.  Example:
              MMAAIILLPPAATTHH='/var/mail/bfox?"You  have  mail":~/shell-mail?"$_  has
              mail!"'
              BBaasshh can be configured to supply a default value for this  vari-
              able  (there  is  no  value by default), but the location of the
              user  mail  files  that  it  uses  is  system  dependent  (e.g.,
              /var/mail/$$UUSSEERR).
       OOPPTTEERRRR If set to the value 1, bbaasshh displays error messages generated by
              the ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS  below).
              OOPPTTEERRRR  is  initialized to 1 each time the shell is invoked or a
              shell script is executed.
       PPAATTHH   The search path for commands.  It is a colon-separated  list  of
              directories  in  which the shell looks for commands (see CCOOMMMMAANNDD
              EEXXEECCUUTTIIOONN below).  A zero-length (null) directory  name  in  the
              value of PPAATTHH indicates the current directory.  A null directory
              name may appear as two adjacent colons,  or  as  an  initial  or
              trailing  colon.   The  default path is system-dependent, and is
              set by the administrator who installs bbaasshh.  A common value is
              ``/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
       PPOOSSIIXXLLYY__CCOORRRREECCTT
              If this variable is in the environment  when  bbaasshh  starts,  the
              shell  enters _p_o_s_i_x _m_o_d_e before reading the startup files, as if
              the ----ppoossiixx invocation option had been supplied.  If it  is  set
              while  the  shell is running, bbaasshh enables _p_o_s_i_x _m_o_d_e, as if the
              command _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 set, the value is executed as a command prior to issuing each
              primary prompt.
       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
              execution  trace.   The first character of the expanded value of
              PPSS44 is replicated multiple times, as necessary, to indicate mul-
              tiple levels of indirection.  The default is ``++ ''.
       SSHHEELLLL  The full pathname to the shell is kept in this environment vari-
              able.  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
              default 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  is  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.  When assigning to indexed arrays, 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 subscript is required.

       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
       introduced  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
       expansion of the first parameter is joined with the beginning  part  of
       the  original  word,  and the expansion of the last parameter is joined
       with the last part of the original word.   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 ele-
       ments in the array.  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 inter-
       preted 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]
       destroys the array element at index _s_u_b_s_c_r_i_p_t,  for  both  indexed  and
       associative  arrays.   Negative subscripts to indexed arrays are inter-
       preted 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, or 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 @@, removes the
       entire array.

       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
       described  above,  the  argument  is subject to pathname expansion.  If
       pathname 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
       array.  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
       increase  the number of words of the expansion; other expansions expand
       a single word to a single word.  The only exceptions to  this  are  the
       expansions  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 characters, 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  pre-
       fixed  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 neces-
       sary.  When characters are supplied, the  expression  expands  to  each
       character  lexicographically  between  _x  and  _y,  inclusive, using the
       default C locale.  Note that both _x and _y must be  of  the  same  type.
       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
       expression.   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
       replaces 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
       assignments  to  PPAATTHH,  MMAAIILLPPAATTHH, and CCDDPPAATTHH, and the shell assigns the
       expanded 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
       embedded  arithmetic  expansion,  command  substitution,  or  parameter
       expansion.

       ${_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
       expansion,  parameter  expansion,  command substitution, and arithmetic
       expansion.  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
       below  (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
       unset.

       ${_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
              expansion 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
              parameters 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
              expansion  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 ::-- expan-
              sion.

              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
              undefined results.

              Substring indexing is zero-based unless the  positional  parame-
              ters  are  used,  in  which  case  the  indexing  starts at 1 by
              default.  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
              substituted  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  substi-
              tuted  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 interpreted as relative to one greater than the maxi-
              mum 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 ele-
              ment.

       ${_p_a_r_a_m_e_t_e_r##_w_o_r_d}
       ${_p_a_r_a_m_e_t_e_r####_w_o_r_d}
              RReemmoovvee mmaattcchhiinngg pprreeffiixx ppaatttteerrnn.  The _w_o_r_d is expanded to produce
              a pattern just as in pathname expansion, and matched against the
              expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt--
              tteerrnn  MMaattcchhiinngg  below.   If the pattern matches the beginning of
              the value of _p_a_r_a_m_e_t_e_r, then the result of the expansion is  the
              expanded  value  of _p_a_r_a_m_e_t_e_r with the shortest matching pattern
              (the ``##'' case) or the longest  matching  pattern  (the  ``####''
              case)  deleted.   If  _p_a_r_a_m_e_t_e_r  is  @@ or **, the pattern removal
              operation is applied to each positional parameter in  turn,  and
              the  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 expan-
              sion 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
              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  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}
              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.   The match is performed using the rules described under
              PPaatttteerrnn MMaattcchhiinngg below.  If _p_a_t_t_e_r_n begins with //,  all  matches
              of  _p_a_t_t_e_r_n  are  replaced with _s_t_r_i_n_g.  Normally only the first
              match is replaced.  If _p_a_t_t_e_r_n begins with ##, 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
              begins with %%, it must match at the end of the expanded value of
              _p_a_r_a_m_e_t_e_r.   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  nnooccaasseemmaattcchh
              shell  option  is enabled, the match is performed 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 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 substitu-
              tion 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}
       ${_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  ^^
              operator  converts  lowercase letters matching _p_a_t_t_e_r_n to upper-
              case; the ,, operator converts matching uppercase letters to low-
              ercase.  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
              omitted, 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 sub-
              scripted 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:

              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.
              aa      The expansion is a string consisting of flag values  rep-
                     resenting _p_a_r_a_m_e_t_e_r's attributes.

              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 is treated as if it were within  double  quotes,  but  a
       double  quote  inside  the  parentheses  is not treated specially.  All
       tokens in the expression undergo parameter and variable expansion, com-
       mand  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
       results 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,  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  PPaatt--
       tteerrnn  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 performed  without
       regard  to  the  case of alphabetic characters.  When a pattern is used
       for pathname expansion, the character ````..''''  at the start of a name  or
       immediately  following  a  slash must be matched explicitly, unless the
       shell option ddoottgglloobb is set.  The filenames  ````..''''   and  ````....''''   must
       always  be matched explicitly, even if ddoottgglloobb is set.  In other cases,
       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, 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
                     directories 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
                     sequence and character set, is  matched.   If  the  first
                     character following the [[ is a !!  or a ^^ then any charac-
                     ter not enclosed is matched.  The sorting order of  char-
                     acters  in range expressions is determined by the current
                     locale and the values of the LLCC__CCOOLLLLAATTEE or  LLCC__AALLLL  shell
                     variables, if set.  To obtain the traditional interpreta-
                     tion 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
                     using the syntax [[==_c==]], which matches all characters with
                     the same collation weight  (as  defined  by  the  current
                     locale) 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, several
       extended  pattern  matching operators are recognized.  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 fol-
       lowing 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

       Complicated extended pattern matching against  long  strings  is  slow,
       especially  when the patterns contain alternations and the strings con-
       tain 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.  Redirection 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 himself.

       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
       expansion 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
       results from the expansion of _w_o_r_d to be opened for appending  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.

       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
       error:

              &&>>_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
       DDeessccrriippttoorrss 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
       unquoted, all lines of the here-document  are  subjected  to  parameter
       expansion,  command substitution, and arithmetic expansion, the charac-
       ter sequence \\<<nneewwlliinnee>> is ignored, and \\ must be  used  to  quote  the
       characters \\, $$, and ``.

       If the redirection operator is <<<<--, then all leading tab characters are
       stripped from input lines and  the  line  containing  _d_e_l_i_m_i_t_e_r.   This
       allows  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
       descriptor  open for input, a redirection error occurs.  If _w_o_r_d evalu-
       ates 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, a shell function should be  used  (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
       after  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
       interpret  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
       between  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
       remain  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 previous 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,
       defines a maximum function nesting level.   Function  invocations  that
       exceed 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
       before 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 subshells 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
       recursive 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
       operators.  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.

       Constants with a leading 0 are interpreted as octal numbers.  A leading
       0x or  0X  denotes  hexadecimal.   Otherwise,  numbers  take  the  form
       [_b_a_s_e_#]n,  where the optional _b_a_s_e is a decimal number between 2 and 64
       representing the arithmetic base, and _n is a number in that  base.   If
       _b_a_s_e_#  is omitted, then base 10 is used.  When specifying _n, 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 uppercase letters may be used interchangeably  to  repre-
       sent numbers between 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 abd [[ 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
       internally  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
       expansions, assignments, and redirections, from left to right.

       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.  Otherwise, the variables are added to the environ-
       ment of the executed command and do not affect the current shell  envi-
       ronment.   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
       affect 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
       remember  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.  A subshell is spawned 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.

       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
       reset 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
       default  standard  input  for  the command is the empty file _/_d_e_v_/_n_u_l_l.
       Otherwise, the invoked command inherits the  file  descriptors  of  the
       calling 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
       invocation, 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
       ddeeccllaarree  --xx  commands allow parameters and functions to be added to and
       deleted from the environment.  If the value of a parameter in the envi-
       ronment  is  modified,  the  new value becomes part of the environment,
       replacing 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
       returns  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
       invalid options or missing arguments.

       BBaasshh itself returns the exit  status  of  the  last  command  executed,
       unless  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
       ignores 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
       effect, 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
       using 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.

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
       execution 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
       interface 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
       returned  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 ccee job.  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 pre-
       vious  job  with  a --.  A single % (with no accompanying job specifica-
       tion) 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
       exits.

       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 will force wwaaiitt to wait until the job  or  process
       terminates 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
       described  above  before  tracing  each  command  when the --xx option is
       enabled.  BBaasshh allows these prompt strings to be customized by  insert-
       ing  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
                     inserted 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  $$00  (the  portion
                     following the final slash)
              \\tt     the current time in 24-hour HH:MM:SS format
              \\TT     the current time in 12-hour HH:MM:SS format
              \\@@     the current time in 12-hour am/pm format
              \\AA     the current time in 24-hour HH:MM format
              \\uu     the username of the current user
              \\vv     the version of bbaasshh (e.g., 2.00)
              \\VV     the release of bbaasshh, version + patch level (e.g., 2.00.0)
              \\ww     the  current  working  directory,  with $$HHOOMMEE abbreviated
                     with a tilde (uses the value of the PPRROOMMPPTT__DDIIRRTTRRIIMM  vari-
                     able)
              \\WW     the basename of the current working directory, 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
       below),  while  the  command  number is the position in the sequence of
       commands executed during the current shell session.  After  the  string
       is  decoded,  it is expanded via parameter expansion, command substitu-
       tion, 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).

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.  When a program which uses the readline library 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  con-
       structs.  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

       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:

       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.
       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, the user is
              asked  whether or not he wishes to view them; otherwise they are
              simply listed on the terminal.
       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--bbrraacckkeetteedd--ppaassttee ((OOffff))
              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
              arrow 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
              attempts 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.
       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),
              regardless 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
              received  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--ddiirreeccttoorriieess).
       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
              instead 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
                     instance, 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
                     operator  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
                     library  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--ssccrreeeenn ((CC--ll))
              Clear the screen leaving the current 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.
       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
              position (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-
              incremental 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
              inserts 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
              EEXXPPAANNSSIIOONN 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.
       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.
       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 $$VVIISSUUAALL,
              $$EEDDIITTOORR, 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
              argument, uppercase the previous word, but do not move point.
       ddoowwnnccaassee--wwoorrdd ((MM--ll))
              Lowercase  the  current  (or  following)  word.  With a negative
              argument, lowercase the previous word, but do not move point.
       ccaappiittaalliizzee--wwoorrdd ((MM--cc))
              Capitalize the current (or following)  word.   With  a  negative
              argument, 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
              numeric argument, but is otherwise ignored.  As a special  case,
              if  this  command is immediately followed by a character that is
              neither 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
              argument  may  be  used to move backward through the list.  This
              command 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
              removed, the line will be executed by the shell.
       gglloobb--ccoommpplleettee--wwoorrdd ((MM--gg))
              The word before point is  treated  as  a  pattern  for  pathname
              expansion,  with  an asterisk implicitly appended.  This pattern
              is used to generate a list of matching  filenames  for  possible
              completions.
       gglloobb--eexxppaanndd--wwoorrdd ((CC--xx **))
              The  word  before  point  is  treated  as a pattern for pathname
              expansion, and the  list  of  matching  filenames  is  inserted,
              replacing  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
       option 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  ($$11)  is  the  name of the command whose arguments are
       being completed, the second argument ($$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
       defined, 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
       default 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
       unwritable,  the  history is not saved.  If the HHIISSTTTTIIMMEEFFOORRMMAATT variable
       is set, time stamps are written to the history file,  marked  with  the
       history  comment  character, so they may be preserved across shell ses-
       sions.  This uses the history comment character  to  distinguish  time-
       stamps from other history lines.  After saving the history, the history
       file is truncated to contain no more than HHIISSTTFFIILLEESSIIZZEE lines.  If HHIISSTT--
       FFIILLEESSIIZZEE  is  unset,  or set to null, a non-numeric value, or a numeric
       value less than zero, the history file is not truncated.

       The builtin command ffcc (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) may  be  used
       to list or edit and re-execute a portion of the history list.  The hhiiss--
       ttoorryy builtin may be used to display or  modify  the  history  list  and
       manipulate  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
       options.

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
       account.  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
       expansion character is also treated as quoted if  it  immediately  pre-
       cedes 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
       option 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.
       ^^_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
              expand to the zeroth word if there is only one word in the line.
       %%      The word matched by the most recent `?_s_t_r_i_n_g?' search.
       _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 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 `:'.

       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.
       ss//_o_l_d//_n_e_w//
              Substitute  _n_e_w  for  the  first  occurrence of _o_l_d in the event
              line.  Any delimiter can be used  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 sin-
              gle 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 substitu-
              tions took place, the last _s_t_r_i_n_g in a !!??_s_t_r_i_n_g[[??]]  search.
       &&      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' 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
              environment 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.  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 posi-
              tional parameters when  _f_i_l_e_n_a_m_e  is  executed.   Otherwise  the
              positional  parameters  are  unchanged.   If  the  --TT  option is
              enabled, ssoouurrccee inherits any trap on DDEEBBUUGG; if it  is  not,  any
              DDEEBBUUGG  trap  string  is  saved  and  restored around the call to
              ssoouurrccee, and ssoouurrccee unsets the DDEEBBUUGG trap while it executes.   If
              --TT  is not set, and the sourced file changes the DDEEBBUUGG trap, the
              new value is retained when ssoouurrccee 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
              returns 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
              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
              appear  in  _._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
                     entered.  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 variable  to  the
                     current location of the insertion point.  If the executed
                     command changes  the  value  of  RREEAADDLLIINNEE__LLIINNEE  or  RREEAADD--
                     LLIINNEE__PPOOIINNTT,  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
                     input.

              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
              exited.  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.  Any addi-
              tional arguments following _d_i_r are ignored.  The variable CCDDPPAATTHH
              defines  the  search path for the directory containing _d_i_r: each
              directory name in  CCDDPPAATTHH  is  searched  for  _d_i_r.   Alternative
              directory  names in CCDDPPAATTHH are separated by a colon (:).  A null
              directory name in CCDDPPAATTHH is the same as the  current  directory,
              i.e., ``..''.  If _d_i_r begins with a slash (/), then CCDDPPAATTHH 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 symbolic links
              to be followed by resolving the link after processing  instances
              of _._. in _d_i_r.  If _._. appears in _d_i_r, it is processed 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  success-
              fully  determined  after  a successful directory change, ccdd will
              return an unsuccessful status.  On systems that support it,  the
              --@@  option  presents  the  extended attributes associated with a
              file as a directory.  An argument of -- is converted  to  $$OOLLDDPPWWDD
              before the directory change is attempted.  If a non-empty direc-
              tory name from CCDDPPAATTHH is used, or if -- is  the  first  argument,
              and the directory change is successful, the absolute pathname of
              the new working directory is written  to  the  standard  output.
              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
              option 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
              facilities, while available, will not have useful values.

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

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

       ccoommpplleettee  [--aabbccddeeffggjjkkssuuvv] [--oo _c_o_m_p_-_o_p_t_i_o_n] [--DDEEII] [--AA _a_c_t_i_o_n] [--GG _g_l_o_b_-
       _p_a_t] [--WW _w_o_r_d_l_i_s_t] [--FF _f_u_n_c_t_i_o_n] [--CC _c_o_m_m_a_n_d]
              [--XX _f_i_l_t_e_r_p_a_t] [--PP _p_r_e_f_i_x] [--SS _s_u_f_f_i_x] _n_a_m_e [_n_a_m_e _._._.]
       ccoommpplleettee --pprr [--DDEEII] [_n_a_m_e ...]
              Specify how arguments to each _n_a_m_e should be completed.  If  the
              --pp  option  is supplied, or if no options 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  inital
              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
                              default)  to  words  completed at the end of the
                              line.
                      pplluussddiirrss
                              After any matches defined by  the  compspec  are
                              generated,    directory   name   completion   is
                              attempted 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  ($$11)  is  the name of the command whose
                      arguments are being completed, the second argument  ($$22)
                      is the word being completed, and the third argument ($$33)
                      is the word preceding the word being  completed  on  the
                      current  command  line.   When it finishes, the possible
                      completions are retrieved from the value of the  CCOOMMPPRREE--
                      PPLLYY 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
              options 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
              described above.  The --DD option indicates  that  other  supplied
              options 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  inital 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
              enclosing 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 [--aaAAffFFggiillnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
       ttyyppeesseett [--aaAAffFFggiillnnrrttuuxx] [--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
              attributes 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 function.  It is ignored in all other cases.  The  follow-
              ing options can be used to restrict output to variables with the
              specified attribute 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
                     inherit 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
                     environment.

              Using  `+'  instead of `-' turns off the attribute instead, with
              the exceptions that ++aa may not be used to destroy an array vari-
              able  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 vari-
              able 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 assignment
              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
              assign  a  value to an array variable without using the compound
              assignment 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
              directories.   The  default  display  is  on  a single line with
              directory 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 directory in the stack.
              --cc     Clears  the  directory  stack  by  deleting  all  of  the
                     entries.
              --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
              receives 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 argument 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
              escape  characters  by  default.   eecchhoo does not interpret ---- to
              mean the end of options.  eecchhoo interprets the  following  escape
              sequences:
              \\aa     alert (bell)
              \\bb     backspace
              \\cc     suppress further output
              \\ee
              \\EE     an escape character
              \\ff     form feed
              \\nn     new line
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\\\     backslash
              \\00_n_n_n  the  eight-bit  character  whose value is the octal value
                     _n_n_n (zero to three octal digits)
              \\xx_H_H   the eight-bit character whose value  is  the  hexadecimal
                     value _H_H (one or two hex digits)
              \\uu_H_H_H_H the  Unicode (ISO/IEC 10646) character whose value is the
                     hexadecimal value _H_H_H_H (one to four hex digits)
              \\UU_H_H_H_H_H_H_H_H
                     the Unicode (ISO/IEC 10646) character whose value is  the
                     hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits)

       eennaabbllee [--aa] [--ddnnppss] [--ff _f_i_l_e_n_a_m_e] [_n_a_m_e ...]
              Enable  and disable builtin shell commands.  Disabling a builtin
              allows a disk command which has the same name as a shell builtin
              to  be  executed without specifying a full pathname, even though
              the shell normally searches for builtins before  disk  commands.
              If  --nn  is  used,  each  _n_a_m_e  is disabled; otherwise, _n_a_m_e_s are
              enabled.  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.
              The --dd option will delete a builtin previously loaded  with  --ff.
              If no _n_a_m_e arguments are given, or if the --pp option is supplied,
              a list of shell builtins is printed.  With no other option argu-
              ments,  the  list consists of all enabled shell builtins.  If --nn
              is supplied, only disabled builtins are printed.  If --aa is  sup-
              plied,  the  list printed includes all builtins, with an indica-
              tion of whether or not each is enabled.  If --ss is supplied,  the
              output  is restricted to the POSIX _s_p_e_c_i_a_l builtins.  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).  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 other-
              wise.  If _f_i_r_s_t is not specified, it is set to the previous com-
              mand 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
              invalid  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_s]
              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
              expected 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
              option  requires  an argument, ggeettooppttss places that argument into
              the variable OOPPTTAARRGG.  The shell does not reset OOPPTTIINNDD  automati-
              cally;  it  must  be  manually  reset  between multiple calls to
              ggeettooppttss within the same shell invocation if a new set of parame-
              ters is to be used.

              When  the  end  of  options is encountered, ggeettooppttss exits with a
              return 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 given in _a_r_g_s, ggeettooppttss parses those instead.

              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
              OOPPTTAARRGG 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
              option causes the shell to forget  the  remembered  location  of
              each  _n_a_m_e.   If the --tt option is supplied, the full pathname to
              which each _n_a_m_e corresponds is printed.  If multiple _n_a_m_e  argu-
              ments  are  supplied  with  --tt,  the  _n_a_m_e is printed before the
              hashed full pathname.  The --ll option causes output  to  be  dis-
              played in a format that may be reused as input.  If no arguments
              are given, or if only --ll is supplied, information  about  remem-
              bered  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  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
                     appended 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 is sup-
              plied as an argument to --dd, or the history expansion supplied 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
              executes _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
              option 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.
              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.  With no arguments,
              removes the top directory from the stack, and performs a  ccdd  to
              the new top directory.  Arguments, if supplied, have the follow-
              ing meanings:
              --nn     Suppresses the normal change of directory  when  removing
                     directories  from  the  stack,  so that only the stack is
                     manipulated.
              ++_n     Removes the _nth entry counting from the left of the  list
                     shown  by  ddiirrss, starting with zero.  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 ppooppdd command is successful, a ddiirrss is performed as well,
              and the return status is 0.  ppooppdd returns false  if  an  invalid
              option is encountered, the directory stack is empty, a non-exis-
              tent directory stack entry is specified, or the directory change
              fails.

       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.
              %%((_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
                     argument is specified, conversion behaves as  if  -1  had
                     been  given.   This  is  an exception to the usual pprriinnttff
                     behavior.

              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
              directories and returns 0, unless the directory stack is  empty.
              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, making it the
                     new current working directory as if it had been  supplied
                     as the argument to the ccdd builtin.

              If the ppuusshhdd command is successful, a ddiirrss is performed as well.
              If the first form is used, ppuusshhdd returns 0 unless the cd to  _d_i_r
              fails.   With the second form, ppuusshhdd returns 0 unless the direc-
              tory stack is empty, a non-existent directory stack  element  is
              specified,  or the directory change to the specified new current
              directory fails.

       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
              invalid 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
              descriptor _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
              second _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
              (described 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
                     ignored.
              --dd _d_e_l_i_m
                     The  first  character  of  _d_e_l_i_m is used to terminate the
                     input 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
                     returns  immediately,  without  trying  to read any data.
                     The exit status is 0 if input is available on the  speci-
                     fied  file descriptor, non-zero otherwise.  The exit sta-
                     tus 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 is assigned to the vari-
              able  RREEPPLLYY.   The  exit  status  is zero, unless end-of-file is
              encountered, rreeaadd times out (in which case the status is greater
              than  128),  a variable assignment error (such as assigning to a
              readonly variable) occurs, or an invalid file descriptor is sup-
              plied 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
              arrays;  the  --AA  option  restricts the variables to associative
              arrays.  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
              rreettuurrnn is executed by a trap handler, the last command  used  to
              determine  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
              executed 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
              significant 8 bits.  The return status is non-zero if rreettuurrnn  is
              supplied  a  non-numeric argument, or is used outside a function
              and not during execution of a script by .. or ssoouurrccee.   Any  com-
              mand  associated  with the RREETTUURRNN trap is executed before execu-
              tion resumes 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, the name and value of each shell  variable  are
              displayed in a format that can be reused as input for setting or
              resetting the currently-set variables.  Read-only variables can-
              not  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
              arguments remaining after option processing are treated as  val-
              ues for the positional parameters and are assigned, in order, to
              $$11, $$22, ......  $$_n.  Options,  if  specified,  have  the  following
              meanings:
              --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
                      ignored by interactive shells.
              --oo _o_p_t_i_o_n_-_n_a_m_e
                      The _o_p_t_i_o_n_-_n_a_m_e can be one of the following:
                      aalllleexxppoorrtt
                              Same as --aa.
                      bbrraacceeeexxppaanndd
                              Same as --BB.
                      eemmaaccss   Use an emacs-style command line  editing  inter-
                              face.  This is enabled by default when the shell
                              is interactive, unless the shell is started with
                              the  ----nnooeeddiittiinngg  option.  This also affects the
                              editing interface used for rreeaadd --ee.
                      eerrrreexxiitt Same as --ee.
                      eerrrrttrraaccee
                              Same as --EE.
                      ffuunnccttrraaccee
                              Same as --TT.
                      hhaasshhaallll Same as --hh.
                      hhiisstteexxppaanndd
                              Same as --HH.
                      hhiissttoorryy Enable command history, as described above under
                              HHIISSTTOORRYY.  This option is on by default in inter-
                              active shells.
                      iiggnnoorreeeeooff
                              The  effect  is  as   if   the   shell   command
                              ``IGNOREEOF=10''  had  been  executed (see SShheellll
                              VVaarriiaabblleess above).
                      kkeeyywwoorrdd Same as --kk.
                      mmoonniittoorr Same as --mm.
                      nnoocclloobbbbeerr
                              Same as --CC.
                      nnooeexxeecc  Same as --nn.
                      nnoogglloobb  Same as --ff.
                      nnoolloogg   Currently ignored.
                      nnoottiiffyy  Same as --bb.
                      nnoouunnsseett Same as --uu.
                      oonneeccmmdd  Same as --tt.
                      pphhyyssiiccaall
                              Same as --PP.
                      ppiippeeffaaiill
                              If set, the return value of a  pipeline  is  the
                              value  of  the  last (rightmost) command to exit
                              with a non-zero status, or zero if all  commands
                              in  the pipeline exit successfully.  This option
                              is disabled by default.
                      ppoossiixx   Change the behavior of bbaasshh  where  the  default
                              operation  differs  from  the  POSIX standard to
                              match the standard (_p_o_s_i_x _m_o_d_e).  See  SSEEEE  AALLSSOO
                              below for a reference to a document that details
                              how posix mode affects bash's behavior.
                      pprriivviilleeggeedd
                              Same as --pp.
                      vveerrbboossee Same as --vv.
                      vvii      Use a vi-style command line  editing  interface.
                              This also affects the editing interface used for
                              rreeaadd --ee.
                      xxttrraaccee  Same as --xx.
                      If --oo is supplied with no _o_p_t_i_o_n_-_n_a_m_e, 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
                      appear 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.
              --tt      Exit after reading and executing one command.
              --uu      Treat unset variables and parameters other than the spe-
                      cial parameters "@" and "*" 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
                      executed 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
              options  can  also be specified as arguments to an invocation of
              the shell.  The current set of options may be found in $$--.   The
              return 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 $$##-_n+1 are
              unset.  _n must be a non-negative number less than  or  equal  to
              $$##.   If  _n is 0, no parameters are changed.  If _n is not given,
              it is assumed to be 1.  If _n is greater than $$##, the  positional
              parameters  are  not changed.  The return status is greater than
              zero if _n is greater than $$## 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
              options 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
              options, 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
                      associative array subscripts during  arithmetic  expres-
                      sion  evaluation  and  while executing builtins that can
                      perform variable assignments.
              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
                      exiting 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
                      If set, bbaasshh changes its behavior to that of version 3.1
                      with respect to quoted arguments to the  [[[[  conditional
                      command's ==~~ operator and locale-specific string compar-
                      ison when using the [[[[ conditional  command's  <<  and  >>
                      operators.   Bash  versions  prior to bash-4.1 use ASCII
                      collation and _s_t_r_c_m_p(3); bash-4.1 and later use the cur-
                      rent locale's collation sequence and _s_t_r_c_o_l_l(3).
              ccoommppaatt3322
                      If set, bbaasshh changes its behavior to that of version 3.2
                      with respect to locale-specific string  comparison  when
                      using  the  [[[[  conditional  command's << and >> operators
                      (see previous item) and the  effect  of  interrupting  a
                      command  list.   Bash  versions 3.2 and earlier continue
                      with the next command in the list after  one  terminates
                      due to an interrupt.
              ccoommppaatt4400
                      If set, bbaasshh changes its behavior to that of version 4.0
                      with respect to locale-specific string  comparison  when
                      using  the  [[[[  conditional  command's << and >> operators
                      (see description of ccoommppaatt3311) and the effect  of  inter-
                      rupting  a  command  list.   Bash versions 4.0 and later
                      interrupt the list as if the shell received  the  inter-
                      rupt;  previous  versions continue with the next command
                      in the list.
              ccoommppaatt4411
                      If set, bbaasshh, when in _p_o_s_i_x _m_o_d_e, treats a single  quote
                      in  a  double-quoted  parameter  expansion  as a special
                      character.  The single quotes must match (an  even  num-
                      ber)  and  the  characters between the single quotes are
                      considered quoted.  This is the behavior of  posix  mode
                      through  version 4.1.  The default bash behavior remains
                      as in previous versions.
              ccoommppaatt4422
                      If set, bbaasshh does not process the replacement string  in
                      the  pattern  substitution  word  expansion  using quote
                      removal.
              ccoommppaatt4433
                      If set, bbaasshh does not print  a  warning  message  if  an
                      attempt  is  made to use a quoted compound array assign-
                      ment as an argument to  ddeeccllaarree,  makes  word  expansion
                      errors  non-fatal  errors that cause the current command
                      to fail (the default behavior  is  to  make  them  fatal
                      errors that cause the shell to exit), and does not reset
                      the loop state when a shell function is  executed  (this
                      allows  bbrreeaakk  or ccoonnttiinnuuee in a shell function to affect
                      loops in the caller's context).
              ccoommppaatt4444
                      If  set,  bbaasshh  saves  the  positional   parameters   to
                      BASH_ARGV and BASH_ARGC before they are used, regardless
                      of whether or not extended debugging mode is enabled.
              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
                      expand  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,  arrange  to  execute  the
                      debugger  profile  before the shell starts, identical to
                      the ----ddeebbuuggggeerr option.  If set after invocation,  behav-
                      ior 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
                      description of  FFIIGGNNOORREE.   This  option  is  enabled  by
                      default.
              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
                      sequence  is  not taken into account, so bb will not col-
                      late between AA and  BB,  and  upper-case  and  lower-case
                      ASCII characters will collate together.
              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
                      exits, 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
                      option 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
                      attribute 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
                      attempt 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.
              nnuullllgglloobb
                      If set, bbaasshh allows patterns which match no  files  (see
                      PPaatthhnnaammee  EExxppaannssiioonn  above)  to expand to a null string,
                      rather than themselves.
              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
                      using the  command  word  resulting  from  the  expanded
                      alias.
              pprroommppttvvaarrss
                      If set, prompt strings undergo parameter expansion, com-
                      mand  substitution,  arithmetic  expansion,  and   quote
                      removal  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
                      restricted 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.
              xxppgg__eecchhoo
                      If  set,  the  eecchhoo  builtin  expands   backslash-escape
                      sequences 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
              depends 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
                     If the first argument is !!, the result is the negation of
                     the three-argument expression composed of  the  remaining
                     arguments.  Otherwise, the expression is parsed and eval-
                     uated 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
              receives  signal(s)  _s_i_g_s_p_e_c.   If _a_r_g is absent (and there is a
              single _s_i_g_s_p_e_c) or --, each specified  signal  is  reset  to  its
              original  disposition  (the  value  it  had upon entrance to the
              shell).  If _a_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  commands  associated  with each signal.  The --ll option
              causes the shell to print a list of signal names and their  cor-
              responding  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)
              option.

              Signals ignored upon entry to the shell  cannot  be  trapped  or
              reset.   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
              returned.  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 speci-
              fied as a command name, or nothing if ``type -t name'' would not
              return  _f_i_l_e.  The --PP option forces a PPAATTHH search for each _n_a_m_e,
              even if ``type -t name'' would not 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 [--HHSSaabbccddeeffiikkllmmnnppqqrrssttuuvvxxPPTT [_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,
              respectively.  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 are printed before the value.  Other options are inter-
              preted as follows:
              --aa     All current limits are reported
              --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
              --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; --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 incre-
              ments.  The return status is 0 unless an invalid option or argu-
              ment 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, any function with that name is  unset.   Each
              unset  variable  or  function  is  removed  from the environment
              passed to subsequent commands.  If any of CCOOMMPP__WWOORRDDBBRREEAAKKSS,  RRAANN--
              DDOOMM, SSEECCOONNDDSS, LLIINNEENNOO, HHIISSTTCCMMDD, FFUUNNCCNNAAMMEE, GGRROOUUPPSS, or DDIIRRSSTTAACCKK 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.

       wwaaiitt [--ffnn] [_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, all currently active child pro-
              cesses are waited for, and the return status is zero.  If the --nn
              option  is  supplied,  wwaaiitt  waits  for any job to terminate and
              returns its exit status.  If the --ff option is supplied, and  job
              control is enabled, wwaaiitt forces _i_d to terminate 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.

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, 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
              --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 sseett ++oo rreessttrriicctteedd.

       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
       _~_/_._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_/.

       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 5.0                    2018 October 22                        BASH(1)
