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.  These  are
       referred  to  as  _a_s_y_n_c_h_r_o_n_o_u_s commands.  Commands separated by a ;; are
       executed sequentially; the shell waits for each command to terminate in
       turn.   The  return  status is the exit status of the last command exe-
       cuted.

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

              _c_o_m_m_a_n_d_1 &&&& _c_o_m_m_a_n_d_2

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

       An OR list has the form

              _c_o_m_m_a_n_d_1 |||| _c_o_m_m_a_n_d_2

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

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

       (_l_i_s_t) _l_i_s_t is executed in a subshell 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 and ++AA may not be used to destroy array
              variables and ++rr will not remove the readonly  attribute.   When
              used in a function, ddeeccllaarree and ttyyppeesseett make each _n_a_m_e local, as
              with the llooccaall command, unless the --gg option is supplied.  If  a
              variable  name  is followed by =_v_a_l_u_e, the value of the variable
              is set to _v_a_l_u_e.  When using --aa or --AA and the  compound  assign-
              ment  syntax to create array variables, additional attributes do
              not take effect until subsequent assignments.  The return  value
              is 0 unless an invalid option is encountered, an attempt is made
              to define a function using ``-f foo=bar'', an attempt is made to
              assign  a  value  to  a readonly variable, an attempt is made to
              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, while executing builtins that can  per-
                      form  variable assignments, and while executing builtins
                      that perform array dereferencing.
              aauuttooccdd  If set, a command name that is the name of  a  directory
                      is  executed  as  if it were the argument to the ccdd com-
                      mand.  This option is only used by interactive shells.
              ccddaabbllee__vvaarrss
                      If set, an argument to the ccdd builtin  command  that  is
                      not  a directory is assumed to be the name of a variable
                      whose value is the directory to change to.
              ccddssppeellll If set, minor errors in the spelling of a directory com-
                      ponent  in  a  ccdd command will be corrected.  The errors
                      checked for are transposed characters, a missing charac-
                      ter,  and  one  character  too many.  If a correction is
                      found, the corrected filename is printed, and  the  com-
                      mand  proceeds.  This option is only used by interactive
                      shells.
              cchheecckkhhaasshh
                      If set, bbaasshh checks that a command found in the hash ta-
                      ble  exists  before  trying  to execute it.  If a hashed
                      command no longer exists, a normal path search  is  per-
                      formed.
              cchheecckkjjoobbss
                      If set, bbaasshh lists the status of any stopped and running
                      jobs before exiting an interactive shell.  If  any  jobs
                      are running, this causes the exit to be deferred until a
                      second exit is attempted without an intervening  command
                      (see  JJOOBB  CCOONNTTRROOLL  above).   The shell always postpones
                      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 December 7                        BASH(1)
