BASH(1)                                                                BASH(1)



NNAAMMEE
       bash - GNU Bourne-Again SHell

SSYYNNOOPPSSIISS
       bbaasshh [options] [file]

CCOOPPYYRRIIGGHHTT
       Bash is Copyright (C) 1989-2004 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 IEEE POSIX
       Shell and Tools specification (IEEE Working Group 1003.2).

OOPPTTIIOONNSS
       In addition to the single-character shell  options  documented  in  the
       description  of  the sseett builtin command, bbaasshh interprets the following
       options when it is invoked:

       --cc _s_t_r_i_n_g If the --cc option is present,  then  commands  are  read  from
                 _s_t_r_i_n_g.   If  there  are arguments after the _s_t_r_i_n_g, they are
                 assigned to the positional parameters, starting with $$00.
       --ii        If the --ii option is present, the shell is _i_n_t_e_r_a_c_t_i_v_e.
       --ll        Make bbaasshh act as if it had been invoked as a login shell (see
                 IINNVVOOCCAATTIIOONN below).
       --rr        If  the  --rr  option  is present, the shell becomes _r_e_s_t_r_i_c_t_e_d
                 (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).
       --ss        If the --ss option is present, or if no arguments remain  after
                 option  processing,  then commands are read from the standard
                 input.  This option allows the positional  parameters  to  be
                 set when invoking an interactive shell.
       --DD        A  list of all double-quoted strings preceded by $$ is printed
                 on the standard ouput.  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)  and  shell
              function tracing (see the description of the --oo ffuunnccttrraaccee option
              to the sseett builtin below).
       ----dduummpp--ppoo--ssttrriinnggss
              Equivalent to --DD, but the  output  is  in  the  GNU  _g_e_t_t_e_x_t  ppoo
              (portable object) file format.
       ----dduummpp--ssttrriinnggss
              Equivalent to --DD.
       ----hheellpp Display  a  usage  message  on standard output and exit success-
              fully.
       ----iinniitt--ffiillee _f_i_l_e
       ----rrccffiillee _f_i_l_e
              Execute commands from _f_i_l_e instead of the standard personal ini-
              tialization  file  _~_/_._b_a_s_h_r_c  if  the  shell is interactive (see
              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 1003.2 standard  to  match  the  standard  (_p_o_s_i_x
              _m_o_d_e).

       ----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  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  file  names  as  described  below  under  TTiillddee
       EExxppaannssiioonn 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  a  login  shell  exits, 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  by  the  remote  shell
       daemon,  usually  _r_s_h_d.  If bbaasshh determines it is being run by _r_s_h_d, 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 _r_s_h_d does not 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  variable, if it appears in the environment, is 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
       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  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 the char-
       acter ||.  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).

       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.  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.

       Each command in a pipeline is executed as a separate process (i.e.,  in
       a subshell).

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

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

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

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

       The control operators &&&& and |||| denote AND lists and OR lists,  respec-
       tively.  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.

       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:

       (_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.

       ((_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  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.  The return
              value is 0 if the string matches or does not match the  pattern,
              respectively,  and  1 otherwise.  Any part of the pattern may be
              quoted to force it 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 an extended regular  expres-
              sion 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 conditional
              expression's return value is 2.  If the shell option  nnooccaasseegglloobb
              is enabled, the match is performed without regard to the case of
              alphabetic  characters.   Substrings  matched  by  parenthesized
              subexpressions  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
              expression.  The element of BBAASSHH__RREEMMAATTCCHH with  index  _n  is  the
              portion  of the string matching the _nth parenthesized subexpres-
              sion.

              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
              displayed  again.   If  EOF is read, the command completes.  Any
              other value read causes _n_a_m_e to be set to null.  The  line  read
              is saved in the variable RREEPPLLYY.  The _l_i_s_t is executed after each
              selection until a bbrreeaakk command is executed.  The exit status of
              sseelleecctt  is the exit status of the last command executed in _l_i_s_t,
              or zero if no commands were executed.

       ccaassee _w_o_r_d iinn [ [(] _p_a_t_t_e_r_n [ || _p_a_t_t_e_r_n ] ... ) _l_i_s_t ;; ] ... eessaacc
              A ccaassee command first expands _w_o_r_d, and tries to match it against
              each _p_a_t_t_e_r_n in turn, using the same matching rules as for path-
              name expansion (see PPaatthhnnaammee EExxppaannssiioonn below).  When a match  is
              found,  the  corresponding  _l_i_s_t  is  executed.  After the first
              match, no subsequent matches are attempted.  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; ddoo _l_i_s_t; ddoonnee
       uunnttiill _l_i_s_t; ddoo _l_i_s_t; ddoonnee
              The wwhhiillee command continuously executes the ddoo _l_i_s_t as  long  as
              the  last  command  in _l_i_s_t returns an exit status of zero.  The
              uunnttiill command is identical to the wwhhiillee command, except that the
              test  is  negated;  the  ddoo _l_i_s_t is executed as long as the last
              command in _l_i_s_t returns a non-zero exit status.  The exit status
              of  the  wwhhiillee and uunnttiill commands is the exit status of the last
              ddoo _l_i_s_t command executed, or zero if none was executed.

   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:

       [ 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.  _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.  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 executed, the exit status of
              a function is the exit status of the last  command  executed  in
              the body.  (See FFUUNNCCTTIIOONNSS below.)

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

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

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

       When  the command history expansion facilities are being used, 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 $$, ``, and \\.
       The characters $$ and ``  retain  their  special  meaning  within  double
       quotes.   The  backslash retains its special meaning 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 back-
       slash.  When command history is being used, the double quote may not be
       used to quote the history expansion character.

       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 specifed by the
       ANSI C standard.  Backslash escape sequences, if present,  are  decoded
       as follows:
              \\aa     alert (bell)
              \\bb     backspace
              \\ee     an escape character
              \\ff     form feed
              \\nn     new line
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\\\     backslash
              \\''     single quote
              \\_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)
              \\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  ($$)  will  cause  the
       string  to  be translated according to the current locale.  If the cur-
       rent 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.

   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 occurs within double quotes, it expands to a sin-
              gle word with the value of each parameter separated by the first
              character of the IIFFSS special variable.  That is, "$$**" is equiva-
              lent to "$$11_c$$22_c......", where _c is the first character of the value
              of  the IIFFSS variable.  If IIFFSS is unset, the parameters are sepa-
              rated by spaces.  If IIFFSS is  null,  the  parameters  are  joined
              without intervening separators.
       @@      Expands  to  the positional parameters, starting from one.  When
              the  expansion  occurs  within  double  quotes,  each  parameter
              expands to a separate word.  That is, "$$@@" is equivalent to "$$11"
              "$$22" ...  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 status of the most recently executed foreground
              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).
       $$      Expands to the process ID of the shell.  In a  ()  subshell,  it
              expands  to  the  process  ID of the current shell, not the sub-
              shell.
       !!      Expands to the process ID of the most  recently  executed  back-
              ground (asynchronous) command.
       00      Expands  to  the name of the shell or shell script.  This is set
              at shell initialization.  If bbaasshh is invoked with a file of com-
              mands,  $$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 file name used to invoke bbaasshh, as given  by  argument
              zero.
       __      At  shell startup, set to the absolute file name of the shell or
              shell script being executed as  passed  in  the  argument  list.
              Subsequently,  expands to the last argument to the previous com-
              mand, after expansion.  Also set to the full file name  of  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 file name used to invoke this instance of
              bbaasshh.
       BBAASSHH__AARRGGCC
              An array variable whose values are the number of  parameters  in
              each frame of the current bash 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.
       BBAASSHH__AARRGGVV
              An  array  variable containing all of the parameters in the cur-
              rent bash 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.
       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   corresponding   to   each   member   of  @var{FUNCNAME}.
              $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}} is the line number in the source  file  where
              $${{FFUUNNCCNNAAMMEE[[_$_i  _+  _1]]}} was called.  The corresponding source file
              name is $${{BBAASSHH__SSOOUURRCCEE[[_$_i _+ _1]]}}..  UUssee LLIINNEENNOO ttoo oobbttaaiinn  tthhee  ccuurr--
              rreenntt lliinnee nnuummbbeerr..
       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  corre-
              sponding to the elements in the FFUUNNCCNNAAMMEE array variable.
       BBAASSHH__SSUUBBSSHHEELLLL
              Incremented  by one each time a subshell or subshell environment
              is spawned.  The initial 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
              functions invoked by the programmable completion facilities (see
              PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).

       CCOOMMPP__LLIINNEE
              The current command line.  This variable is  available  only  in
              shell  functions  and  external  commands  invoked  by  the pro-
              grammable 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 pro-
              grammable completion  facilities  (see  PPrrooggrraammmmaabbllee  CCoommpplleettiioonn
              below).

       CCOOMMPP__WWOORRDDBBRREEAAKKSS
              The  set  of characters that the Readline 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.  This variable is avail-
              able only in shell functions invoked by the programmable comple-
              tion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).

       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.

       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  is  "main".  This variable exists only when a
              shell function is executing.  Assignments to  FFUUNNCCNNAAMMEE  have  no
              effect  and  return  an  error status.  If FFUUNNCCNNAAMMEE is unset, it
              loses its special properties, even if it is subsequently  reset.

       GGRROOUUPPSS An  array  variable  containing  the list of groups of which the
              current user is a member.  Assignments to GGRROOUUPPSS have no  effect
              and  return  an  error status.  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.

       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.

       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__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  file  name.
              PPAATTHH is not used to search for the resultant file name.
       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".
       CCOOLLUUMMNNSS
              Used by the sseelleecctt builtin command  to  determine  the  terminal
              width  when  printing  selection  lists.  Automatically set upon
              receipt of a SIGWINCH.
       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).
       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.
       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:~".
       GGLLOOBBIIGGNNOORREE
              A colon-separated list of patterns defining the set of filenames
              to be ignored by pathname expansion.  If a filename 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 an interactive 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.   The  default  value  is  500.  The history file is also
              truncated to this size after  writing  it  when  an  interactive
              shell exits.
       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.
       HHIISSTTSSIIZZEE
              The  number  of commands to remember in the command history (see
              HHIISSTTOORRYY below).  The default value is 500.
       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.
       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, bbaasshh attempts to read _/_e_t_c_/_h_o_s_t_s to obtain the list of
              possible  hostname  completions.   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).
       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 $$.
       LLCC__NNUUMMEERRIICC
              This variable determines the locale  category  used  for  number
              formatting.
       LLIINNEESS  Used  by  the  sseelleecctt  builtin  command  to determine the column
              length for printing selection  lists.   Automatically  set  upon
              receipt of a SIGWINCH.
       MMAAIILL   If  this  parameter is set to a file name and the MMAAIILLPPAATTHH vari-
              able is not set, bbaasshh informs the user of the arrival of mail in
              the specified file.
       MMAAIILLCCHHEECCKK
              Specifies  how  often  (in  seconds)  bbaasshh checks for mail.  The
              default is 60 seconds.  When it is time to check for  mail,  the
              shell  does  so  before  displaying the primary prompt.  If this
              variable is unset, or set to  a  value  that  is  not  a  number
              greater than or equal to zero, the shell disables mail checking.
       MMAAIILLPPAATTHH
              A colon-separated list of file names to  be  checked  for  mail.
              The message to be printed when mail arrives in a particular file
              may be specified by separating the file name  from  the  message
              with a `?'.  When used in the text of the message, $$__ expands to
              the name of the current mailfile.  Example:
              MMAAIILLPPAATTHH='/var/mail/bfox?"You  have  mail":~/shell-mail?"$_  has
              mail!"'
              BBaasshh  supplies  a default value for this variable, but the loca-
              tion of the user mail files that it  uses  is  system  dependent
              (e.g., /var/mail/$$UUSSEERR).
       OOPPTTEERRRR If set to the value 1, bbaasshh displays error messages generated by
              the ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS  below).
              OOPPTTEERRRR  is  initialized to 1 each time the shell is invoked or a
              shell script is executed.
       PPAATTHH   The search path for commands.  It is a colon-separated  list  of
              directories  in  which the shell looks for commands (see CCOOMMMMAANNDD
              EEXXEECCUUTTIIOONN below).  A zero-length (null) directory  name  in  the
              value of PPAATTHH indicates the current directory.  A null directory
              name may appear as two adjacent colons,  or  as  an  initial  or
              trailing  colon.   The  default path is system-dependent, and is
              set by the administrator who installs bbaasshh.  A common  value  is
              ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.
       PPOOSSIIXXLLYY__CCOORRRREECCTT
              If  this  variable  is  in the environment when bbaasshh starts, the
              shell enters _p_o_s_i_x _m_o_d_e before reading the startup files, as  if
              the  ----ppoossiixx  invocation option had been supplied.  If it is set
              while the shell is running, bbaasshh enables _p_o_s_i_x _m_o_d_e, as  if  the
              command _s_e_t _-_o _p_o_s_i_x had been executed.
       PPRROOMMPPTT__CCOOMMMMAANNDD
              If set, the value is executed as a command prior to issuing each
              primary prompt.
       PPSS11    The value of this parameter is expanded  (see  PPRROOMMPPTTIINNGG  below)
              and  used  as  the  primary prompt string.  The default value is
              ``\\ss--\\vv\\$$ ''.
       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 PPSS44 is replicated  mul-
              tiple  times, as necessary, to indicate multiple levels of indi-
              rection.  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%%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 input after
              issuing the primary prompt.  BBaasshh terminates after  waiting  for
              that number of seconds if input does not arrive.

       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
              %% 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  array  variables.  Any variable may be
       used as an 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 contiguously.  Arrays  are  indexed
       using integers and are zero-based.

       An  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 greater than or
       equal to zero.  To explicitly declare an array,  use  ddeeccllaarree  --aa  _n_a_m_e
       (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS 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.  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.  Only _s_t_r_i_n_g is required.  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.  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.

       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.   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 expan-
       sion is the number of elements in  the  array.   Referencing  an  array
       variable without a subscript is equivalent to referencing element zero.

       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.  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.

       The  ddeeccllaarree,  llooccaall,  and rreeaaddoonnllyy builtins each accept a --aa option to
       specify an array.  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,  parame-
       ter,  variable  and arithmetic expansion and command substitution (done
       in a left-to-right fashion), word splitting, and pathname expansion.

       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.

       Only brace expansion, word splitting, and pathname expansion can change
       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[[@@]]}}" 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}}, where _x and _y are either
       integers or single characters.  When integers are supplied, the expres-
       sion  expands  to each number between _x and _y, inclusive.  When charac-
       ters are supplied, the expression expands  to  each  character  lexico-
       graphically between _x and _y, inclusive.  Note that both _x and _y must be
       of the same type.

       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.

       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 ==.  In these cases, tilde expansion is also per-
       formed.   Consequently,  one  may use file names with tildes in assign-
       ments to PPAATTHH, MMAAIILLPPAATTHH, and CCDDPPAATTHH, and the shell assigns the expanded
       value.

   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 paramter expan-
       sion.

       ${_p_a_r_a_m_e_t_e_r}
              The value of _p_a_r_a_m_e_t_e_r is substituted.  The braces are  required
              when  _p_a_r_a_m_e_t_e_r  is  a  positional  parameter with more than one
              digit, or when _p_a_r_a_m_e_t_e_r is followed by a character which is not
              to be interpreted as part of its name.

       If the first character of _p_a_r_a_m_e_t_e_r is an exclamation point, a level of
       variable indirection is introduced.  BBaasshh uses the value of  the  vari-
       able  formed  from  the  rest of _p_a_r_a_m_e_t_e_r as the name of the variable;
       this variable is then expanded and that value is used in  the  rest  of
       the  substitution,  rather than the value of _p_a_r_a_m_e_t_e_r itself.  This is
       known as _i_n_d_i_r_e_c_t _e_x_p_a_n_s_i_o_n.  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, bbaasshh tests for a parameter that is
       unset or null; omitting the colon results in a test only for a  parame-
       ter 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
              _p_a_r_a_m_e_t_e_r starting at the character  specified  by  _o_f_f_s_e_t.   If
              _l_e_n_g_t_h  is omitted, expands to the substring of _p_a_r_a_m_e_t_e_r start-
              ing at the character specified by _o_f_f_s_e_t.  _l_e_n_g_t_h and _o_f_f_s_e_t are
              arithmetic   expressions   (see  AARRIITTHHMMEETTIICC  EEVVAALLUUAATTIIOONN  below).
              _l_e_n_g_t_h must evaluate to a number greater than or equal to  zero.
              If  _o_f_f_s_e_t  evaluates  to  a number less than zero, the value is
              used as an offset from the end of the value  of  _p_a_r_a_m_e_t_e_r.   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.  If _p_a_r_a_m_e_t_e_r is an array name indexed 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]}.   Substring  indexing  is  zero-based
              unless  the  positional  parameters  are used, in which case the
              indexing starts at 1.

       ${!!_p_r_e_f_i_x**}
       ${!!_p_r_e_f_i_x@@}
              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.

       ${!!_n_a_m_e[_@]}
       ${!!_n_a_m_e[_*]}
              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}
              The  length  in  characters of the value of _p_a_r_a_m_e_t_e_r is substi-
              tuted.  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 substituted is  the  number  of
              elements in the array.

       ${_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}
              The  _w_o_r_d  is  expanded to produce a pattern just as in pathname
              expansion.  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 expansion is the  resultant
              list.

       ${_p_a_r_a_m_e_t_e_r%%_w_o_r_d}
       ${_p_a_r_a_m_e_t_e_r%%%%_w_o_r_d}
              The  _w_o_r_d  is  expanded to produce a pattern just as in pathname
              expansion.  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  pat-
              tern  (the  ``%%''  case)  or  the  longest matching pattern (the
              ``%%%%'' case) deleted.  If _p_a_r_a_m_e_t_e_r  is  @@  or  **,  the  pattern
              removal  operation  is  applied  to each positional parameter in
              turn, and the expansion is the resultant list.  If _p_a_r_a_m_e_t_e_r  is
              an  array  variable subscripted with @@ or **, the pattern removal
              operation is applied to each member of the array  in  turn,  and
              the expansion is the resultant list.

       ${_p_a_r_a_m_e_t_e_r//_p_a_t_t_e_r_n//_s_t_r_i_n_g}
       ${_p_a_r_a_m_e_t_e_r////_p_a_t_t_e_r_n//_s_t_r_i_n_g}
              The _p_a_t_t_e_r_n is expanded to produce a pattern 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.  In the first
              form, only the first match is replaced.  The second form  causes
              all  matches  of _p_a_t_t_e_r_n to be replaced with _s_t_r_i_n_g.  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 _p_a_r_a_m_e_t_e_r is @@ or **, the substitution  operation
              is  applied to each positional parameter in turn, and the expan-
              sion is the resultant list.  If _p_a_r_a_m_e_t_e_r is an  array  variable
              subscripted  with  @@ or **, the substitution operation is applied
              to each member of the array in turn, and the  expansion  is  the
              resultant list.

   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 and replacing the com-
       mand  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 command 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 expansion, string expansion,
       command  substitution, and quote removal.  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 is supported on systems that support  named  pipes
       (_F_I_F_O_s)  or the //ddeevv//ffdd method of naming open files.  It takes the form
       of <<((_l_i_s_t)) or >>((_l_i_s_t)).  The process _l_i_s_t is run with its input or  out-
       put connected to a _F_I_F_O or some file in //ddeevv//ffdd.  The name of this file
       is passed as an argument to the current command as the  result  of  the
       expansion.   If the >>((_l_i_s_t)) form is used, writing to the file will pro-
       vide 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.

       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 on these characters.  If IIFFSS
       is  unset,  or its value is exactly <<ssppaaccee>><<ttaabb>><<nneewwlliinnee>>, the default,
       then any sequence of IIFFSS characters serves to delimit  words.   If  IIFFSS
       has  a  value  other than the default, then sequences of the whitespace
       characters ssppaaccee and ttaabb are ignored at the beginning and  end  of  the
       word,  as  long  as the whitespace character is in the value of IIFFSS (an
       IIFFSS whitespace character).  Any  character  in  IIFFSS  that  is  not  IIFFSS
       whitespace, along with any adjacent IIFFSS whitespace characters, delimits
       a field.  A sequence of IIFFSS whitespace characters is also treated as  a
       delimiter.  If the value of IIFFSS is null, no word splitting occurs.

       Explicit  null  arguments  (""""  or '''') are retained.  Unquoted implicit
       null arguments, resulting from the expansion of parameters that have no
       values,  are  removed.  If a parameter with no value is expanded within
       double quotes, a null argument results and is retained.

       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 file names matching the pattern.  If no
       matching file names are found, and the shell option  nnuullllgglloobb  is  dis-
       abled,  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 alpha-
       betic 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.   When  matching  a  pathname,  the slash character must always be
       matched explicitly.  In  other  cases,  the  ````..''''   character  is  not
       treated  specially.   See  the  description  of sshhoopptt below under SSHHEELLLL
       BBUUIILLTTIINN CCOOMMMMAANNDDSS for a description of the nnooccaasseegglloobb,  nnuullllgglloobb,  ffaaiill--
       gglloobb, 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.  The file names ````..''''  and ````....''''  are always
       ignored  when GGLLOOBBIIGGNNOORREE is set and not null.  However, setting GGLLOOBBIIGG--
       NNOORREE to a non-null value has the effect of enabling the  ddoottgglloobb  shell
       option, so all other file names beginning with a ````..''''  will match.  To
       get the old behavior of ignoring file names  beginning  with  a  ````..'''',
       make  ````..**''''  one of the patterns in GGLLOOBBIIGGNNOORREE.  The ddoottgglloobb option is
       disabled when GGLLOOBBIIGGNNOORREE is unset.

       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.
       ??      Matches any single character.
       [[......]]  Matches any one of the enclosed characters.  A pair  of  charac-
              ters separated by a hyphen denotes a _r_a_n_g_e _e_x_p_r_e_s_s_i_o_n; any char-
              acter that sorts between those two characters, 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  character not enclosed is matched.  The sorting order
              of characters in range expressions is determined by the  current
              locale  and  the value of the LLCC__CCOOLLLLAATTEE shell variable, if set.
              A -- may be matched by including it as the first or last  charac-
              ter 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.2 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  char-
              acter _.

              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  colla-
              tion  weight (as defined by the current locale) as the character
              _c.

              Within [[ and ]], the syntax [[.._s_y_m_b_o_l..]] matches the collating sym-
              bol _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 exactly one of the given patterns
              !!((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches anything except one of the given patterns

   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  may
       also  be  used  to open and close files for the current shell execution
       environment.  The following redirection operators may precede or appear
       anywhere within a _s_i_m_p_l_e _c_o_m_m_a_n_d or may follow a _c_o_m_m_a_n_d.  Redirections
       are processed in the order they appear, from left to right.

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

       The word following the redirection operator in the  following  descrip-
       tions,  unless  otherwise noted, is subjected to brace expansion, tilde
       expansion, parameter expansion, command substitution, arithmetic expan-
       sion,  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 as standard output before the standard output 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:

              //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 a TCP connection to the corresponding 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 a UDP connection to the corresponding socket.

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

   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
       redirection is attempted even if the file named by _w_o_r_d exists.

   AAppppeennddiinngg RReeddiirreecctteedd OOuuttppuutt
       Redirection  of  output  in  this  fashion  causes  the file whose name
       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
       BBaasshh allows both the standard output (file descriptor 1) and the  stan-
       dard  error  output  (file  descriptor  2) to be redirected to the file
       whose name is the expansion of _w_o_r_d with this construct.

       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

   HHeerree DDooccuummeennttss
       This type of redirection instructs the shell to  read  input  from  the
       current  source  until  a  line  containing only _w_o_r_d (with no trailing
       blanks) is seen.  All of the lines read up to that point are then  used
       as the standard input for a command.

       The format of here-documents is:

              <<<<[--]_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 expansion, command substitution, arithmetic expansion, or
       pathname expansion is performed on _w_o_r_d.  If any characters in _w_o_r_d are
       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, com-
       mand substitution, and arithmetic expansion.  In the latter  case,  the
       character  sequence  \\<<nneewwlliinnee>> is ignored, and \\ must be used to quote
       the characters \\, $$, and ``.

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

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

              <<<<<<_w_o_r_d

       The _w_o_r_d is expanded and supplied to the command on its standard input.

   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
       redirection error occurs.  As a special case, if _n is omitted, and _w_o_r_d
       does not expand to one or more digits, 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
       before executing any  of  the  commands  on  that  line.   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 com-
       pound command.  As a consequence, aliases defined in a function are not
       available  until  after  that function is executed.  To be safe, always
       put alias definitions on a separate line, and do not use aalliiaass in  com-
       pound 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 0 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 the exception that the DDEEBBUUGG trap (see the description of the ttrraapp
       builtin under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) is 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 trap).

       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 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.  Note  that  shell  functions  and
       variables  with  the same name may result in multiple identically-named
       entries in the environment passed to the shell's children.  Care should
       be taken in cases where this may cause a problem.

       Functions  may  be  recursive.   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 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 following 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
       ++++_i_d ----_i_d
              variable pre-increment and pre-decrement
       -- ++    unary minus and plus
       !! ~~    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 integer 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 _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 omit-
       ted, then base 10 is used.  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 interchangably to represent 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.  Expressions are formed from the  following
       unary  or  binary  primaries.   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.

       --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.
       --OO _f_i_l_e
              True if _f_i_l_e exists and is owned by the effective user id.
       --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.
       --SS _f_i_l_e
              True if _f_i_l_e exists and is a socket.
       --NN _f_i_l_e
              True  if  _f_i_l_e  exists  and  has been modified since it was last
              read.
       _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.
       _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.
       --oo _o_p_t_n_a_m_e
              True  if  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.
       --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
              True if the strings are equal.  == may be used in place of ==== for
              strict POSIX compliance.

       _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  in  the
              current locale.

       _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 in the
              current locale.

       _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.

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 prints an error message  and  returns
       an exit status 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 asyn-
       chronous 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 invocation.  Builtin commands that are invoked as part of a pipeline
       are also executed in a subshell environment.  Changes made to the  sub-
       shell environment cannot affect the shell's execution environment.

       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 file name of the command and passed to that command in  its  envi-
       ronment.

EEXXIITT SSTTAATTUUSS
       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.

       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  0for which a trap has been set, the trap will not be executed until
       the command completes.  When bbaasshh is waiting for an  asynchronous  com-
       mand  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  status greater than 128, immediately after which the trap is exe-
       cuted.

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 system'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
       write to the terminal.  Background processes which attempt to read from
       (write to) the terminal are sent a SSIIGGTTTTIINN ((SSIIGGTTTTOOUU)) signal by the ter-
       minal 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 name.  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  exam-
       ple, %%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  back-
       ground.   The  _p_r_e_v_i_o_u_s _j_o_b may be referenced using %%--.  In output per-
       taining to jobs (e.g., the output of the jjoobbss command), the current job
       is always flagged with a ++, and the previous job with a --.

       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, the shell
       prints a warning message.  The jjoobbss command may then be used to inspect
       their status.  If a second attempt to exit is made without an interven-
       ing command, the shell does not print another warning, and the  stopped
       jobs are terminated.

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 allows these prompt
       strings to be customized by inserting  a  number  of  backslash-escaped
       special characters that are decoded as follows:
              \\aa     an ASCII bell character (07)
              \\dd     the  date  in "Weekday Month Date" format (e.g., "Tue May
                     26")
              \\DD{{_f_o_r_m_a_t}}
                     the _f_o_r_m_a_t is passed to _s_t_r_f_t_i_m_e(3)  and  the  result  is
                     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
              \\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.
       By default, the line editing commands are similar to those of emacs.  A
       vi-style line editing interface is also available.  To  turn  off  line
       editing  after  the shell is running, use the ++oo eemmaaccss or ++oo vvii options
       to the sseett builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

   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.
       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.
       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--iiggnnoorree--ccaassee ((OOffff))
              If set to OOnn, readline performs filename matching and completion
              in a case-insensitive fashion.
       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).
       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.
       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.
       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.
       eexxppaanndd--ttiillddee ((OOffff))
              If set  to  oonn,  tilde  expansion  is  performed  when  readline
              attempts word completion.
       hhiissttoorryy--pprreesseerrvvee--ppooiinntt
              If  set  to  oonn, the history code attempts to place point at the
              same location on each history line retrived  with  pprreevviioouuss--hhiiss--
              ttoorryy or nneexxtt--hhiissttoorryy.
       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  high  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.
       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.
       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,  unless the leading `.' is supplied by the
              user in the filename to be completed.
       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.
       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.
       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.
       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 extends to the end of the  line;
              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 the both 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.

              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
                     Bash:

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

       $$eennddiiff This command, as seen in the previous example, terminates an $$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).
       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.
       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.
       yyaannkk--llaasstt--aarrgg ((MM--..,, MM--__))
              Insert  the last argument to the previous command (the last word
              of the  previous  history  entry).   With  an  argument,  behave
              exactly  like  yyaannkk--nntthh--aarrgg.   Successive calls to yyaannkk--llaasstt--aarrgg
              move back through the history list, inserting the last  argument
              of each line in turn.
       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.  Any
              argument is ignored.
       eeddiitt--aanndd--eexxeeccuuttee--ccoommmmaanndd ((CC--xxCC--ee))
              Invoke an editor on the current command line,  and  execute  the
              result  as  shell  commands.   BBaasshh  attempts to invoke $$FFCCEEDDIITT,
              $$EEDDIITTOORR, and _e_m_a_c_s as the editor, in that order.

   CCoommmmaannddss ffoorr CChhaannggiinngg TTeexxtt
       ddeelleettee--cchhaarr ((CC--dd))
              Delete the character at point.  If point is at the beginning  of
              the  line,  there  are  no  characters in the line, and the last
              character typed was not bound to ddeelleettee--cchhaarr, then return EEOOFF.
       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.
       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 or 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.
       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.
       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.

   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--uuppppeerrccaassee--vveerrssiioonn ((MM--aa,, MM--bb,, MM--_x,, ......))
              If the metafied character _x is lowercase, run the  command  that
              is bound to the corresponding uppercase character.
       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.
       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 file names 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 file names 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 ouput.  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.
       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  pro-
       grammable completion facilities are invoked.

       First,  the command name is identified.  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.

       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 filename 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,  arithmetic  expansion,  and
       pathname  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 com-
       pleted, 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  and  CCOOMMPP__PPOOIINNTT  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
       is the name of the command whose arguments  are  being  completed,  the
       second  argument is the word being completed, and the third argument is
       the word preceding the word being  completed  on  the  current  command
       line.  No filtering of the generated completions 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.

       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.

       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.

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.  When an inter-
       active  shell  exits, the last $$HHIISSTTSSIIZZEE lines are copied from the his-
       tory list to $$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  over-
       written.   If  HHIISSTTFFIILLEE is unset, or if the history file is unwritable,
       the history is not saved.  After saving the history, the  history  file
       is  truncated to contain no more than HHIISSTTFFIILLEESSIIZZEE lines.  If HHIISSTTFFIILLEE--
       SSIIZZEE is not set, no truncation is performed.

       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.  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  available  to  manipulate  the  selected
       words.  The line is broken into words in the same fashion as when read-
       ing 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.  History expansions are introduced by
       the appearance of the  history  expansion  character,  which  is  !!  by
       default.   Only  backslash  (\\) and single quotes can quote the history
       expansion character.

       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), and rreeaadd--
       lliinnee 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 sub-
       stitution will be reloaded into the rreeaaddlliinnee editing buffer for correc-
       tion.   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).

   EEvveenntt DDeessiiggnnaattoorrss
       An  event designator is a reference to a command line entry in the his-
       tory 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 line 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 starting with _s_t_r_i_n_g.
       !!??_s_t_r_i_n_g[[??]]
              Refer to the most recent command containing _s_t_r_i_n_g.  The  trail-
              ing ?? may be omitted if _s_t_r_i_n_g is followed immediately by a new-
              line.
       ^^_s_t_r_i_n_g_1^^_s_t_r_i_n_g_2^^
              Quick substitution.  Repeat the last 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 MMoodd--
              iiffiieerrss 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 argument.
       %%      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 file name component, leaving only the head.
       tt      Remove all leading file name 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.
       :: [_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.  A zero exit code  is
              returned.

        ..  _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, file
              names 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.  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 the 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, if _j_o_b_s_p_e_c was not found or started  without  job  con-
              trol.

       bbiinndd [--mm _k_e_y_m_a_p] [--llppssvvPPSSVV]
       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 _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; _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.
              --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.
              --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.
              --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.

              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 the shell is not executing
              a loop when bbrreeaakk is executed.

       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.

       ccdd [--LL||--PP] [_d_i_r]
              Change the current directory to _d_i_r.  The variable HHOOMMEE  is  the
              default  _d_i_r.   The  variable CCDDPPAATTHH defines the search path for
              the directory containing _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 says to use the physical directory structure  instead  of
              following  symbolic  links  (see  also  the --PP option to the sseett
              builtin command); the --LL option forces symbolic links to be fol-
              lowed.   An  argument  of -- is equivalent to $$OOLLDDPPWWDD.  If a non-
              empty directory 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 success-
              fully changed; false otherwise.

       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.

       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 file  name
              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 pro-
              grammable completion code had generated  them  directly  from  a
              completion specification with the same flags.  If _w_o_r_d is speci-
              fied, 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] [--AA _a_c_t_i_o_n] [--GG _g_l_o_b_p_a_t] [--WW
       _w_o_r_d_l_i_s_t] [--PP _p_r_e_f_i_x] [--SS _s_u_f_f_i_x]
              [--XX _f_i_l_t_e_r_p_a_t] [--FF _f_u_n_c_t_i_o_n] [--CC _c_o_m_m_a_n_d] _n_a_m_e [_n_a_m_e _._._.]
       ccoommpplleettee --pprr [_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 process of applying  these  completion  specifications  when
              word  completion  is  attempted  is  described  above under PPrroo--
              ggrraammmmaabbllee 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 or suppressing trailing spaces).  Intended
                              to be used with shell functions.
                      nnoossppaaccee Tell  readline  not  to  append  a  space   (the
                              default)  to  words  completed at the end of the
                              line.
              --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.
              --GG _g_l_o_b_p_a_t
                      The  filename  expansion  pattern _g_l_o_b_p_a_t is expanded to
                      generate the possible completions.
              --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.  The possible completions are  the  members
                      of  the  resultant  list which match the word being com-
                      pleted.
              --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 it finishes, the possible  com-
                      pletions  are  retrieved from the value of the CCOOMMPPRREEPPLLYY
                      array variable.
              --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  filename  expansion.
                      It  is  applied  to  the  list  of  possible completions
                      generated 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.
              --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.

              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.

       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 the shell is not
              executing a loop when ccoonnttiinnuuee is executed.

       ddeeccllaarree [--aaffFFiirrttxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
       ttyyppeesseett [--aaffFFiirrttxx] [--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, additional options are ignored.  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 the
              function is defined  are  displayed  as  well.   The  --FF  option
              implies  --ff.  The following options can be used to restrict out-
              put to variables with the specified attribute or to  give  vari-
              ables attributes:
              --aa     Each _n_a_m_e is an array variable (see AArrrraayyss above).
              --ff     Use function names only.
              --ii     The variable is treated as an integer; arithmetic evalua-
                     tion (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN )) is performed  when  the
                     variable is assigned a value.
              --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 trap from the calling shell.  The trace
                     attribute has no special meaning for variables.
              --xx     Mark _n_a_m_es for export  to  subsequent  commands  via  the
                     environment.

              Using  `+'  instead of `-' turns off the attribute instead, with
              the exception that ++aa may not be used to destroy an array  vari-
              able.   When  used in a function, makes each _n_a_m_e local, as with
              the llooccaall command.  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.  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.
              ++_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.
              --cc     Clears  the  directory  stack  by  deleting  all  of  the
                     entries.
              --ll     Produces  a  longer  listing;  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.

              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 ...]
              Without options, each _j_o_b_s_p_e_c  is  removed  from  the  table  of
              active  jobs.   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
              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 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 always 0.  If --nn is specified, the trailing
              newline is suppressed.  If the --ee option is  given,  interpreta-
              tion  of  the following backslash-escaped characters is enabled.
              The --EE option disables the interpretation of these escape  char-
              acters,  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 trailing newline
              \\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)
              \\_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)

       eennaabbllee [--aaddnnppss] [--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 arg 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 cannot be
              executed for some reason, a non-interactive shell exits,  unless
              the  shell  option eexxeeccffaaiill is enabled, in which case it returns
              failure.  An interactive shell returns failure if the file  can-
              not  be executed.  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  all  names  that  are
              exported  in  this  shell  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 supplied with a _n_a_m_e that is not a func-
              tion.

       ffcc [--ee _e_n_a_m_e] [--nnllrr] [_f_i_r_s_t] [_l_a_s_t]
       ffcc --ss [_p_a_t=_r_e_p] [_c_m_d]
              Fix  Command.  In the first form, a range of commands from _f_i_r_s_t
              to _l_a_s_t is selected from the history list.  _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 cur-
              rent 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 otherwise.  If _f_i_r_s_t is not spec-
              ified  it is set to the previous command for editing and -16 for
              listing.

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

              In  the  second form, _c_o_m_m_a_n_d is re-executed after each instance
              of _p_a_t is replaced by _r_e_p.  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 com-
              mand.

              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 nnaammee 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]
              For each _n_a_m_e, the full file name of the command  is  determined
              by searching the directories in $$PPAATTHH and remembered.  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 file name 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 arguments are
              supplied with --tt, the _n_a_m_e is printed  before  the  hashed  full
              pathname.  The --ll option causes output to be displayed in a for-
              mat that may be reused as input.  If no arguments are given,  or
              if only --ll is supplied, information about remembered commands is
              printed.  The return status is true unless a _n_a_m_e is  not  found
              or an invalid option is supplied.

       hheellpp [--ss] [_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.  The --ss option restricts the  information
              displayed  to  a  short  usage synopsis.  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 --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.
              --aa     Append  the  ``new'' history lines (history lines entered
                     since the beginning of the current bbaasshh session)  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 use them as the
                     current history.
              --ww     Write  the current history to the history file, overwrit-
                     ing 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 is set, the time stamp information associ-
              ated with each history entry is written  to  the  history  file.
              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 supplied 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.
              --pp     List  only  the  process  ID  of  the job's process group
                     leader.
              --nn     Display information only about  jobs  that  have  changed
                     status  since the user was last notified of their status.
              --rr     Restrict output to running jobs.
              --ss     Restrict output to 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 [_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.  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).  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.  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.

       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:
              ++_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.
              --nn     Suppresses the normal change of directory  when  removing
                     directories  from  the  stack,  so that only the stack is
                     manipulated.

              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 _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 _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  for-
              mat  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) for-
              mats,  %%bb  causes pprriinnttff to expand backslash escape sequences in
              the corresponding _a_r_g_u_m_e_n_t (except that  \\cc  terminates  output,
              backslashes in \\'', \\"", and \\?? are not removed, and octal escapes
              beginning with \\00 may contain up to four digits), and %%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.

              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] [_d_i_r]
       ppuusshhdd [--nn] [+_n] [-_n]
              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, exchanges the top two directories
              and  returns 0, unless the directory stack is empty.  Arguments,
              if supplied, have the following meanings:
              ++_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.
              --nn     Suppresses the normal change  of  directory  when  adding
                     directories  to  the  stack,  so  that  only the stack is
                     manipulated.
              _d_i_r    Adds _d_i_r to the directory stack at the top, making it the
                     new current working directory.

              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] [--uu _f_d] [--tt _t_i_m_e_o_u_t] [--aa _a_n_a_m_e] [--pp _p_r_o_m_p_t] [--nn _n_c_h_a_r_s] [--dd
       _d_e_l_i_m] [_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, 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, with leftover words and their interven-
              ing separators 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 values.  The characters in IIFFSS  are  used  to
              split  the  line into words.  The backslash character (\\) may be
              used to remove any special meaning for the next  character  read
              and  for line continuation.  Options, if supplied, have the fol-
              lowing 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.
              --ee     If the standard input is coming from a terminal, rreeaaddlliinnee
                     (see RREEAADDLLIINNEE above) is used to obtain the line.
              --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.
              --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 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 is not read within _t_i_m_e_o_u_t seconds.  This
                     option has no effect if rreeaadd is not  reading  input  from
                     the terminal or a pipe.
              --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 return code  is  zero,  unless  end-of-file  is
              encountered,  rreeaadd  times  out, or an invalid file descriptor is
              supplied as the argument to --uu.

       rreeaaddoonnllyy [--aappff] [_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 arrays.  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 --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 vari-
              able 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 func-
              tion.

       rreettuurrnn [_n]
              Causes  a function to exit with the return value specified by _n.
              If _n is omitted, the return status is that of the  last  command
              executed  in the function body.  If 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 used outside a
              function and not during execution of a script by ..,  the  return
              status is false.  Any command associated with the RREETTUURRNN trap is
              executed before execution resumes after the function or  script.

       sseett [----aabbeeffhhkkmmnnppttuuvvxxBBCCHHPP] [--oo _o_p_t_i_o_n] [_a_r_g ...]
              Without  options,  the name and value of each shell variable are
              displayed in a format that can be reused as input.   The  output
              is  sorted  according  to  the current locale.  When options are
              specified, they set or unset shell  attributes.   Any  arguments
              remaining  after the options are processed are treated as values
              for the positional parameters and are assigned, in order, to $$11,
              $$22,  ......   $$_n.   Options, if specified, have the following mean-
              ings:
              --aa      Automatically mark variables  and  functions  which  are
                      modified  or  created  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 _s_i_m_p_l_e _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 in an _i_f statement, part of a &&&& or  ||||
                      list, or if the command's return value is being inverted
                      via !!.  A trap on EERRRR, if set, is  executed  before  the
                      shell exits.
              --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).   Background  pro-
                      cesses  run  in a separate process group and a line con-
                      taining their exit status is printed upon their  comple-
                      tion.
              --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.
                      eerrrrttrraaccee
                              Same as --EE.
                      ffuunnccttrraaccee
                              Same as --TT.
                      eerrrreexxiitt Same as --ee.
                      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 1003.2 standard
                              to match the standard (_`_p_o_s_i_x _m_o_d_e).
                      pprriivviilleeggeedd
                              Same as --pp.
                      vveerrbboossee Same as --vv.
                      vvii      Use a vi-style command line editing interface.
                      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
                      variable,  if it appears in the environment, is 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 supplied, these actions are taken and  the
                      effective user id is set to the real user id.  If the --pp
                      option is supplied 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 as an error when performing param-
                      eter expansion.  If expansion is attempted on  an  unset
                      variable, 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 follow 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 trap on DDEEBBUUGG is inherited  by  shell  func-
                      tions, command substitutions, and commands executed in a
                      subshell environment.  The DDEEBBUUGG trap  is  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 variables controlling optional shell behav-
              ior.  With no options, or with the --pp option, a list of all set-
              table options is displayed, with an indication of whether or not
              each  is  set.  The --pp option causes output to be displayed in a
              form that may be reused as input.  Other options have  the  fol-
              lowing 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,  the  dis-
              play is limited to those options which are set or unset, respec-
              tively.  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:

              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 file name 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.
              cchheecckkwwiinnssiizzee
                      If  set,  bbaasshh checks the window size after each command
                      and, if necessary,  updates  the  values  of  LLIINNEESS  and
                      CCOOLLUUMMNNSS.
              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.
              ddoottgglloobb If  set, bbaasshh includes filenames beginning with a `.' in
                      the results of pathname expansion.
              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,  behavior  intended  for  use  by  debuggers is
                      enabled:
                      11..     The --FF option to the ddeeccllaarree builtin displays the
                             source file name and line number corresponding to
                             each function name supplied as an argument.
                      22..     If the command run by the DDEEBBUUGG  trap  returns  a
                             non-zero  value,  the next command is skipped and
                             not executed.
                      33..     If the command run by the DDEEBBUUGG  trap  returns  a
                             value  of 2, and the shell is executing in a sub-
                             routine (a shell function or a shell script  exe-
                             cuted  by  the  ..  or ssoouurrccee builtins), a call to
                             rreettuurrnn is simulated.
              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.
              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.
              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.
              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.
              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).
              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.
              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.  The --ff option says not to complain if this is  a  login
              shell;  just  suspend anyway.  The return status is 0 unless the
              shell is a login shell and --ff is not supplied, or if job control
              is not enabled.
       tteesstt _e_x_p_r
       [[ _e_x_p_r ]]
              Return  a  status  of  0 or 1 depending on the evaluation of the
              conditional expression _e_x_p_r.  Each operator and operand must  be
              a  separate argument.  Expressions are composed of the primaries
              described above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS.

              Expressions may  be  combined  using  the  following  operators,
              listed in decreasing order of precedence.
              !! _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
                     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.  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.  Otherwise,  the  expression  is  false.
                     The  --aa  and --oo operators are considered binary operators
                     in this case.
              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.

       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 SIG 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 executed before every
              _s_i_m_p_l_e _c_o_m_m_a_n_d, _f_o_r command, _c_a_s_e command, _s_e_l_e_c_t command, 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  eexxttgglloobb  option  to  the sshhoopptt builtin for
              details of its effect on the DDEEBBUUGG trap.  If a _s_i_g_s_p_e_c  is  EERRRR,
              the  command  _a_r_g  is  executed  whenever a simple command has 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 &&&& or |||| list, or
              if the command's return value is being inverted  via  !!.   These
              are  the  same  conditions  obeyed  by the eerrrreexxiitt option.  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.  Signals ignored upon entry to the shell cannot
              be  trapped or reset.  Trapped signals are reset to their origi-
              nal values in a child process when it 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, not necessarily 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  func-
              tion  lookup, as with the ccoommmmaanndd builtin.  ttyyppee returns true if
              any of the arguments are found, false if none are found.

       uulliimmiitt [--SSHHaaccddffllmmnnppssttuuvv [_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 once
              it is set; a soft limit may be increased up to the value of  the
              hard  limit.   If  neither --HH nor --SS is specified, 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 interpreted as fol-
              lows:
              --aa     All current limits are reported
              --cc     The maximum size of core files created
              --dd     The maximum size of a process's data segment
              --ff     The maximum size of files created by the shell
              --ll     The maximum size that may be locked into memory
              --mm     The maximum resident set size
              --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)
              --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

              If _l_i_m_i_t is given, it is the new value of the specified resource
              (the --aa option is display only).  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,
              and  --nn and --uu, which are unscaled values.  The return status is
              0 unless an invalid option or argument is supplied, or an  error
              occurs while setting a new limit.

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

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

       uunnsseett [-ffvv] [_n_a_m_e ...]
              For each _n_a_m_e, remove the corresponding  variable  or  function.
              If no options are supplied, or the --vv option is given, each _n_a_m_e
              refers to a shell variable.   Read-only  variables  may  not  be
              unset.  If --ff is specifed, each _n_a_m_e refers to a shell function,
              and the function definition is removed.  Each unset variable  or
              function  is  removed  from the environment passed to subsequent
              commands.  If any of RRAANNDDOOMM, SSEECCOONNDDSS, LLIINNEENNOO, HHIISSTTCCMMDD, FFUUNNCCNNAAMMEE,
              GGRROOUUPPSS,  or  DDIIRRSSTTAACCKK are unset, they lose their special proper-
              ties, even if they are subsequently reset.  The exit  status  is
              true unless a _n_a_m_e is readonly.

       wwaaiitt [_n]
              Wait  for  the specified process and return its termination sta-
              tus.  _n 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 _n is not given, all currently  active  child  processes
              are waited for, and the return status is zero.  If _n specifies a
              non-existent process or job, the return status is  127.   Other-
              wise,  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  file  name 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 >> redirec-
              tion operators

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

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

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

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

       +o      turning off restricted mode with sseett ++rr or 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
       _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@po.CWRU.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_/_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_@_p_o_._C_W_R_U_._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 pro-
       cess is stopped, the shell immediately executes the next command in the
       sequence.  It suffices to place the sequence of commands between paren-
       theses to force it into a subshell, which may be stopped as a unit.

       Commands inside of $$((...)) command substitution  are  not  parsed  until
       substitution  is attempted.  This will delay error reporting until some
       time after the command is entered.  For example, unmatched parentheses,
       even  inside  shell  comments,  will result in error messages while the
       construct is being read.

       Array variables may not (yet) be exported.



GNU Bash-3.0                     2004 June 26                          BASH(1)
