


BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


NAME
       bash,  :,  .,  alias,  bg, bind, break, builtin, case, cd,
       command, continue, declare, dirs,  disown,  echo,  enable,
       eval,  exec,  exit,  export,  fc,  fg, for, getopts, hash,
       help, history, if, jobs, kill, let, local,  logout,  popd,
       pushd,  pwd,  read,  readonly,  return, set, shift, shopt,
       source, suspend, test, times, trap, type, typeset, ulimit,
       umask,  unalias, unset, until, wait, while - bash built-in
       commands, see bash(1)

BASH BUILTIN COMMANDS
       Unless otherwise noted, each builtin command documented in
       this section as accepting options preceded by -- accepts ----
       to signify the end of the options.
       :: [arguments]
              No effect; the command does nothing beyond  expand-
              ing arguments and performing any specified redirec-
              tions.  A zero exit code is returned.

        ..  filename [arguments]
       source filename [arguments]
              Read and execute commands from filename in the cur-
              rent  shell  environment and return the exit status
              of the last command  executed  from  filename.   If
              filename  does  not  contain a slash, file names in
              PATH are used  to  find  the  directory  containing
              filename.   The  file searched for in PATH need not
              be executable.  The current directory  is  searched
              if  no  file  is  found in PATH.  If the sourcepath
              option to the shopt builtin command is turned  off,
              the  PATH  is  not  searched.  If any arguments are
              supplied, they  become  the  positional  parameters
              when  filename  is  executed.   Otherwise the posi-
              tional 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 filename is not found or cannot be read.

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

       bg [jobspec]
              Resume the suspended job jobspec in the background,
              as if it had been started with &&.   If  jobspec  is



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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              not  present, the shell's notion of the current job
              is used.  bg jobspec returns 0 unless run when  job
              control  is  disabled or, when run with job control
              enabled, if jobspec was not found or started  with-
              out job control.

       bind [-m keymap] [-lpsvPSV]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] keyseq:function-name
              Display current readline key and function bindings,
              or bind a key sequence to a  readline  function  or
              macro.  The binding syntax accepted is identical to
              that of .inputrc, but each binding must  be  passed
              as   a   separate   argument;   e.g.,  '"\C-x\C-r":
              re-read-init-file'.  Options, if supplied, have the
              following meanings:
              -m keymap
                     Use  keymap  as the keymap to be affected by
                     the subsequent bindings.  Acceptable  keymap
                     names are emacs, emacs-standard, emacs-meta,
                     emacs-ctlx, vi, vi-command,  and  vi-insert.
                     vi  is  equivalent  to  vi-command; emacs is
                     equivalent to emacs-standard.
              -l     List the names of all readline functions.
              -p     Display readline function names and bindings
                     in such a way that they can be re-read.
              -P     List  current  readline  function  names and
                     bindings.
              -v     Display readline variable names  and  values
                     in such a way that they can be re-read.
              -V     List  current  readline  variable  names and
                     values.
              -s     Display  readline  key  sequences  bound  to
                     macros and the strings they output in such a
                     way that they can be re-read.
              -S     Display  readline  key  sequences  bound  to
                     macros and the strings they output.
              -f filename
                     Read key bindings from filename.
              -q function
                     Query  about  which  keys  invoke  the named
                     function.
              -u function
                     Unbind all keys bound to the named function.
              -r keyseq
                     Remove any current binding for keyseq.

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

       break [_n]
              Exit from within a for,  while,  until,  or  select
              loop.   If  _n is specified, break _n levels.  _n must



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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              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  exe-
              cuting a loop when break is executed.

       builtin shell-builtin [arguments]
              Execute  the  specified  shell  builtin, passing it
              arguments, and return its  exit  status.   This  is
              useful  when  defining a function whose name is the
              same as a shell builtin, retaining the  functional-
              ity  of  the  builtin  within the function.  The cd
              builtin is commonly redefined this way.  The return
              status  is  false  if  shell-builtin is not a shell
              builtin command.

       cd [-LP] [dir]
              Change the current directory to dir.  The  variable
              HOME  is  the  default  dir.   The  variable CDPATH
              defines the search path for the directory  contain-
              ing dir.  Alternative directory names in CDPATH are
              separated by a colon (:).  A null directory name in
              CDPATH  is the same as the current directory, i.e.,
              ``..''.  If dir begins with a slash (/), then CDPATH
              is not used. The -P option says to use the physical
              directory structure instead of  following  symbolic
              links  (see  also  the -P option to the set builtin
              command); the -L option forces symbolic links to be
              followed.   An argument of -- is equivalent to $OLD-
              PWD.  The return value is true if the directory was
              successfully changed; false otherwise.

       command [-pVv] command [arg ...]
              Run  command with args suppressing the normal shell
              function lookup. Only builtin commands or  commands
              found  in  the PATH are executed.  If the -p option
              is given, the search for command is performed using
              a default value for PATH that is guaranteed to find
              all of the standard utilities.  If either the -V or
              -v  option is supplied, a description of command is
              printed.  The -v option causes a single word  indi-
              cating the command or file name used to invoke com-
              mand to be displayed; the -V option produces a more
              verbose  description.   If  the  -V or -v option is
              supplied, the exit  status  is  0  if  command  was
              found, and 1 if not.  If neither option is supplied
              and an error occurred or command cannot  be  found,
              the exit status is 127.  Otherwise, the exit status
              of the command builtin is the exit status  of  com-
              mand.

       continue [_n]
              Resume  the  next  iteration  of the enclosing for,
              while, until, or select loop.  If _n  is  specified,
              resume  at the _nth enclosing loop.  _n must be >= 1.



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              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 continue is executed.

       declare [-afFirx] [-p] [name[=value]]
       typeset [-afFirx] [-p] [name[=value]]
              Declare  variables and/or give them attributes.  If
              no names are given then display the values of vari-
              ables.   The  -p option will display the attributes
              and values of each name.  When -p  is  used,  addi-
              tional options are ignored.  The -F option inhibits
              the display of function definitions; only the func-
              tion  name  and  attributes  are  printed.   The -F
              option implies -f.  The following  options  can  be
              used to restrict output to variables with the spec-
              ified attribute or to give variables attributes:
              -a     Each name is an array variable  (see  Arrays
                     above).
              -f     Use function names only.
              -i     The  variable  is  treated  as  an  integer;
                     arithmetic evaluation (see ARITHMETIC EVALU-
                     ATION  ))  is  performed when the variable is
                     assigned a value.
              -r     Make names  readonly.   These  names  cannot
                     then   be   assigned  values  by  subsequent
                     assignment statements or unset.
              -x     Mark names for export to subsequent commands
                     via the environment.

              Using  `+'  instead  of `-' turns off the attribute
              instead, with the exception that +a may not be used
              to destroy an array variable.  When used in a func-
              tion, makes each name local, as with the local com-
              mand.   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 vari-
              able without using the compound  assignment  syntax
              (see Arrays above), one of the names is not a valid
              shell variable name, an attempt is made to turn off
              readonly status for a readonly variable, an attempt
              is made to turn off array status for an array vari-
              able,  or an attempt is made to display a non-exis-
              tent function with -f.

       dirs [-clpv] [[++_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
              pushd command; the  popd  command  removes  entries
              from the list.



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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              ++_n     Displays  the  _nth  entry  counting from the
                     left of the list shown by dirs when  invoked
                     without options, starting with zero.
              --_n     Displays  the  _nth  entry  counting from the
                     right of the list shown by dirs when invoked
                     without options, starting with zero.
              -c     Clears  the  directory stack by deleting all
                     of the entries.
              -l     Produces a longer listing; the default list-
                     ing  format  uses a tilde to denote the home
                     directory.
              -p     Print the directory stack with one entry per
                     line.
              -v     Print the directory stack with one entry per
                     line, prefixing 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  direc-
              tory stack.

       disown [-ar] [-h] [jobspec ...]
              Without  options,  each jobspec is removed from the
              table of active jobs.  If the -h option  is  given,
              each  jobspec is not removed from the table, but is
              marked so that SIGHUP is not sent to the job if the
              shell receives a SIGHUP.  If no jobspec is present,
              and neither the -a nor the -r option  is  supplied,
              the  current  job  is  used.  If no jobspec is sup-
              plied, the -a option means to remove  or  mark  all
              jobs;  the  -r  option  without  a jobspec argument
              restricts operation to running  jobs.   The  return
              value  is  0  unless  a  jobspec does not specify a
              valid job.

       echo [-neE] [arg ...]
              Output the args, separated by spaces, followed by a
              newline.   The return status is always 0.  If -n is
              specified, the trailing newline is suppressed.   If
              the  -e option is given, interpretation of the fol-
              lowing  backslash-escaped  characters  is  enabled.
              The  -E option disables the interpretation of these
              escape characters, even on systems where  they  are
              interpreted by default.  echo does not interpret ----
              to mean the end of options.   echo  interprets  the
              following escape sequences:
              \a     alert (bell)
              \b     backspace
              \c     suppress trailing newline
              \e     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab



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              \v     vertical tab
              \\\\     backslash
              \\nnn   the  character whose ASCII code is the octal
                     value nnn (one to three digits)
              \\xxnnn  the character whose ASCII code is  the  hex-
                     adecimal value nnn (one to three digits)

       enable [-adnps] [-f filename] [name ...]
              Enable  and  disable  builtin shell commands.  Dis-
              abling a builtin allows a disk  command  which  has
              the  same  name  as  a shell builtin to be executed
              with specifying a full pathname,  even  though  the
              shell  normally  searches  for builtins before disk
              commands.  If -n is used, each  name  is  disabled;
              otherwise,  names are enabled.  For example, to use
              the test binary found via the PATH instead  of  the
              shell  builtin version, run enable -n test..  The -f
              option means to load the new builtin  command  name
              from  shared  object filename, on systems that sup-
              port dynamic loading.  The -d option will delete  a
              builtin  previously  loaded  with  -f.   If no name
              arguments are given, or if the -p  option  is  sup-
              plied,  a  list of shell builtins is printed.  With
              no other option arguments, the list consists of all
              enabled  shell  builtins.   If -n is supplied, only
              disabled builtins are printed.  If -a is  supplied,
              the  list  printed  includes  all builtins, with an
              indication of whether or not each is  enabled.   If
              -s  is  supplied,  the  output is restricted to the
              POSIX special builtins.   The  return  value  is  0
              unless  a name is not a shell builtin or there is a
              problem loading a new builtin from a shared object.

       eval [arg ...]
              The  args are read and concatenated together into a
              single command.  This command is then read and exe-
              cuted by the shell, and its exit status is returned
              as the value of eval.  If there  are  no  args,  or
              only null arguments, eval returns 0.

       exec [-cl] [-a name] [command [arguments]]
              If command is specified, it replaces the shell.  No
              new process is created.  The arguments  become  the
              arguments  to  command.   If  the -l option is sup-
              plied, the shell places a dash in  the  zeroth  arg
              passed  to  command.   This  is what login(1) does.
              The -c option causes command to be executed with an
              empty  environment.   If  -a is supplied, the shell
              passes name as the zeroth argument to the  executed
              command.   If  command  cannot be executed for some
              reason, a non-interactive shell exits,  unless  the
              shell  option execfail is enabled, in which case it
              returns  failure.   An  interactive  shell  returns
              failure if the file cannot be executed.  If command



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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              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.

       exit [_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  EXIT  is executed
              before the shell terminates.

       export [-fn] [name[=word]] ...
       export -p
              The supplied names are marked for automatic  export
              to  the  environment  of subsequently executed com-
              mands.  If the -f option is given, the names  refer
              to  functions.  If no names are given, or if the -p
              option is supplied, a list of all  names  that  are
              exported  in  this shell is printed.  The -n option
              causes the export property to be removed  from  the
              named  variables.  export returns an exit status of
              0 unless an invalid option is encountered,  one  of
              the names is not a valid shell variable name, or -f
              is supplied with a name that is not a function.

       fc [-e ename] [-nlr] [first] [last]
       fc -s [pat=rep] [cmd]
              Fix Command.  In the first form, a  range  of  com-
              mands  from first to last is selected from the his-
              tory list.  First and last may be  specified  as  a
              string  (to  locate the last command beginning with
              that string) or as a number (an index into the his-
              tory  list,  where  a negative number is used as an
              offset from the current command number).   If  last
              is  not  specified it is set to the current command
              for listing (so that fc -l --1100 prints the  last  10
              commands)  and to first otherwise.  If first is not
              specified it is set to  the  previous  command  for
              editing and -16 for listing.

              The  -n  option suppresses the command numbers when
              listing.  The -r option reverses the order  of  the
              commands.   If the -l option is given, the commands
              are listed on standard output.  Otherwise, the edi-
              tor  given by ename is invoked on a file containing
              those commands.  If ename is not given,  the  value
              of  the  FCEDIT  variable is used, and the value of
              EDITOR if FCEDIT is not set.  If  neither  variable
              is  set,  is  used.   When editing is complete, the
              edited commands are echoed and executed.

              In the second form, command  is  re-executed  after
              each  instance of pat is replaced by rep.  A useful
              alias to use with this  is  ``r=fc  -s'',  so  that



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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              typing  ``r  c'  runs  the last command beginning
              with `c' and typing ``r'' re-executes  the  last
              command.

              If  the  first  form is used, the return value is 0
              unless an invalid option is encountered or first or
              last specify history lines out of range.  If the -e
              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-executed, unless cmd does not  spec-
              ify  a valid history line, in which case fc returns
              failure.

       fg [jobspec]
              Resume jobspec in the foreground, and make  it  the
              current  job.   If  jobspec  is  not  present,  the
              shell's notion of the current  job  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
              jobspec does not specify a  valid  job  or  jobspec
              specifies  a  job that was started without job con-
              trol.

       getopts optstring name [args]
              getopts is used by shell procedures to parse  posi-
              tional  parameters.   optstring contains the option
              letters to be recognized; if a letter  is  followed
              by a colon, the option is expected to have an argu-
              ment, which should be separated from  it  by  white
              space.  Each time it is invoked, getopts places the
              next option in the shell variable name,  initializ-
              ing name if it does not exist, and the index of the
              next argument to be  processed  into  the  variable
              OPTIND.   OPTIND  is initialized to 1 each time the
              shell or a shell script is invoked.  When an option
              requires  an argument, getopts places that argument
              into the variable OPTARG.  The shell does not reset
              OPTIND  automatically;  it  must  be manually reset
              between multiple calls to getopts within  the  same
              shell  invocation  if a new set of parameters is to
              be used.

              When the end of  options  is  encountered,  getopts
              exits  with  a  return  value  greater  than  zero.
              OPTIND is set to the index of the first  non-option
              argument, and name is set to ?.

              getopts  normally parses the positional parameters,
              but if more arguments are given  in  args,  getopts
              parses those instead.




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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              getopts  can  report  errors  in  two ways.  If the
              first character of optstring  is  a  colon,  silent
              error reporting is used.  In normal operation diag-
              nostic messages are printed when invalid options or
              missing  option  arguments are encountered.  If the
              variable OPTERR is set to 0, no error messages will
              be  displayed,  even if the first character of opt-
              string is not a colon.

              If an invalid option is seen, getopts places ? into
              name  and,  if  not silent, prints an error message
              and unsets  OPTARG.   If  getopts  is  silent,  the
              option  character  found is placed in OPTARG and no
              diagnostic message is printed.

              If a required argument is not found, and getopts is
              not  silent, a question mark (??) is placed in name,
              OPTARG  is  unset,  and  a  diagnostic  message  is
              printed.  If getopts is silent, then a colon (::) is
              placed in name and OPTARG  is  set  to  the  option
              character found.

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

       hash [-r] [-p filename] [name]
              For each name, the full file name of the command is
              determined by searching the  directories  in  $PATH
              and  remembered.   If the -p option is supplied, no
              path search is performed, and filename is  used  as
              the  full  file name of the command.  The -r option
              causes the shell to  forget  all  remembered  loca-
              tions.   If  no  arguments  are  given, information
              about remembered commands is printed.   The  return
              status  is  true  unless  a name is not found or an
              invalid option is supplied.

       help [pattern]
              Display helpful information about builtin commands.
              If  pattern  is specified, help gives detailed help
              on all commands matching  pattern;  otherwise  help
              for  all  the builtins and shell control structures
              is printed.  The return status is 0 unless no  com-
              mand matches pattern.

       history [-c] [_n]
       history -anrw [filename]
       history -p arg [arg _._._.]
       history -s arg [arg _._._.]
              With  no  options, display the command history list
              with line numbers.  Lines listed with a ** have been
              modified.   An  argument of _n lists only the last _n
              lines.  If filename is supplied, it is used as  the



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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              name  of  the  history  file;  if not, the value of
              HISTFILE is used.  Options, if supplied,  have  the
              following meanings:
              -a     Append  the  ``new''  history lines (history
                     lines entered since  the  beginning  of  the
                     current bash session) to the history file.
              -n     Read the history lines not already read from
                     the history file into  the  current  history
                     list.   These are lines appended to the his-
                     tory file since the beginning of the current
                     bash session.
              -r     Read  the  contents  of the history file and
                     use them as the current history.
              -w     Write the current  history  to  the  history
                     file,  overwriting  the  history file's con-
                     tents.
              -c     Clear the history list by deleting  all  the
                     entries.
              -p     Perform  history substitution on the follow-
                     ing args and display the result on the stan-
                     dard  output.  Does not store the results in
                     the history list.  Each arg must  be  quoted
                     to disable normal history expansion.
              -s     Store the args in the history list as a sin-
                     gle entry.  The last command in the  history
                     list is removed before the args are added.

              The  return  value is 0 unless an invalid option is
              encountered or an error  occurs  while  reading  or
              writing the history file.

       jobs [-lnprs] [ jobspec ... ]
       jobs -x command [ args ... ]
              The  first form lists the active jobs.  The options
              have the following meanings:
              -l     List process IDs in addition to  the  normal
                     information.
              -p     List  only  the process ID of the job's pro-
                     cess group leader.
              -n     Display information  only  about  jobs  that
                     have  changed status since the user was last
                     notified of their status.
              -r     Restrict output to running jobs.
              -s     Restrict output to stopped jobs.

              If jobspec is given, output is restricted to infor-
              mation  about  that  job.   The  return status is 0
              unless an  invalid  option  is  encountered  or  an
              invalid jobspec is supplied.

              If  the  -x  option  is supplied, jobs replaces any
              jobspec found in command or args  with  the  corre-
              sponding  process  group  ID,  and executes command
              passing it args, returning its exit status.



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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


       kill [-s sigspec | -n signum | --sigspec] [pid | jobspec]
              ...
       kill -l [sigspec | exit__status]
              Send  the  signal named by sigspec or signum to the
              processes named by  pid  or  jobspec.   sigspec  is
              either  a  signal  name such as SIGKILL or a signal
              number; signum is a signal number.  If sigspec is a
              signal  name, the name may be given with or without
              the SIG prefix.  If sigspec is  not  present,  then
              SIGTERM  is  assumed.   An argument of -l lists the
              signal names.  If any arguments are  supplied  when
              -l is given, the names of the signals corresponding
              to the arguments are listed, and the return  status
              is  0.   The exit__status argument to -l is a number
              specifying either a signal number or the exit  sta-
              tus  of  a  process  terminated  by a signal.  kill
              returns true if at least one  signal  was  success-
              fully  sent,  or  false  if  an  error occurs or an
              invalid option is encountered.

       let arg [arg ...]
              Each arg is an arithmetic expression to  be  evalu-
              ated  (see ARITHMETIC EVALUATION).  If the last arg
              evaluates to 0, let returns 1; 0 is returned other-
              wise.

       local [name[=value] ...]
              For  each  argument, a local variable named name is
              created, and assigned value.  When  local  is  used
              within  a  function, it causes the variable name to
              have a visible scope restricted  to  that  function
              and its children.  With no operands, local writes a
              list of local variables to the standard output.  It
              is  an  error  to use local when not within a func-
              tion.  The return status is 0 unless local is  used
              outside a function, or an invalid name is supplied.

       logout Exit a login shell.

       popd [-nn] [+_n] [-_n]
              Removes entries from the directory stack.  With  no
              arguments,  removes  the  top  directory  from  the
              stack, and performs a cd to the new top  directory.
              Arguments,  if  supplied,  have the following mean-
              ings:
              ++_n     Removes the _nth entry counting from the left
                     of  the  list  shown  by dirs, 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  dirs,  starting
                     with zero.  For example: ``popd -0'' removes
                     the last directory, ``popd -1'' the next  to
                     last.



GNU                       1996 March 20                        11





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              -n     Suppresses  the  normal  change of directory
                     when removing directories from the stack, so
                     that only the stack is manipulated.

              If  the  popd command is successful, a dirs is per-
              formed as well, and the return status is  0.   popd
              returns  false if an invalid option is encountered,
              the directory stack is empty, a non-existent direc-
              tory  stack  entry  is  specified, or the directory
              change fails.

       printf format [arguments]
              Write the formatted arguments to the standard  out-
              put under the control of the format.  The format 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 out-
              put,  and  format  specifications,  each  of  which
              causes  printing  of  the next successive argument.
              In addition to the standard printf(1)  formats,  %b
              causes  printf to expand backslash escape sequences
              in the corresponding argument, and %q causes printf
              to  output  the  corresponding argument in a format
              that can be reused as shell input.

              The format is reused as necessary to consume all of
              the  arguments.   If the format requires more argu-
              ments than are supplied, the extra format  specifi-
              cations  behave  as if a zero value or null string,
              as appropriate, had been supplied.

       pushd [-n] [dir]
       pushd [-n] [+_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 argu-
              ments,   exchanges  the  top  two  directories  and
              returns 0, unless the  directory  stack  is  empty.
              Arguments,  if  supplied,  have the following mean-
              ings:
              ++_n     Rotates the stack so that the _nth  directory
                     (counting from the left of the list shown by
                     dirs, 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 dirs, starting with zero) is at the  top.
              -n     Suppresses  the  normal  change of directory
                     when adding directories  to  the  stack,  so
                     that only the stack is manipulated.
              dir    Adds  dir to the directory stack at the top,
                     making it the new current working directory.

              If  the  pushd  command  is  successful,  a dirs is



GNU                       1996 March 20                        12





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              performed as well.  If  the  first  form  is  used,
              pushd  returns  0 unless the cd to dir fails.  With
              the second form, pushd 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.

       pwd [-LP]
              Print the absolute file name of the current working
              directory.  The file name printed contains no  sym-
              bolic  links if the -P option is supplied or the -o
              physical option  to  the  set  builtin  command  is
              enabled.   If the -L option is used, symbolic links
              are followed.  The return status  is  0  unless  an
              error  occurs while reading the name of the current
              directory or an invalid option is supplied.

       read [-er] [-a aname] [-p prompt] [name ...]
              One line is read from the standard input,  and  the
              first  word is assigned to the first name, the sec-
              ond word to the second name, and so on, with  left-
              over   words   and   their  intervening  separators
              assigned to the last  name.   If  there  are  fewer
              words  read from the standard input than names, the
              remaining names are  assigned  empty  values.   The
              characters  in  IFS 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  sup-
              plied, have the following meanings:
              -r     Backslash  does not act as an escape charac-
                     ter.  The backslash is considered to be part
                     of  the  line.   In particular, a backslash-
                     newline pair may not be used as a line  con-
                     tinuation.
              -p     Display  prompt, without a trailing newline,
                     before attempting to read  any  input.   The
                     prompt  is displayed only if input is coming
                     from a terminal.
              -a     The words are assigned to sequential indices
                     of  the array variable aname, starting at 0.
                     aname is unset before  any  new  values  are
                     assigned.  Other name arguments are ignored.
              -e     If the standard input is coming from a  ter-
                     minal, readline (see READLINE above) is used
                     to obtain the line.

              If no names are supplied, the line read is assigned
              to  the  variable  REPLY.  The return code is zero,
              unless end-of-file is encountered.

       readonly [-apf] [name ...]
              The given names are marked readonly; the values  of
              these  names  may  not  be  changed  by  subsequent



GNU                       1996 March 20                        13





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              assignment.  If the  -f  option  is  supplied,  the
              functions corresponding to the names are so marked.
              The -a option restricts the  variables  to  arrays.
              If no name arguments are given, or if the -p option
              is supplied,  a  list  of  all  readonly  names  is
              printed.   The  -p  option causes output to be dis-
              played in a format thatmay be reused as input.  The
              return  status  is  0  unless  an invalid option is
              encountered, one of the names is not a valid  shell
              variable  name,  or -f is supplied with a name that
              is not a function.

       return [_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  func-
              tion  body.  If used outside a function, but during
              execution of a script by the ..   (source)  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 sta-
              tus of the script.  If used outside a function  and
              not  during  execution of a script by .., the return
              status is false.

       set [--abefhkmnptuvxBCHP] [-o option] [arg ...]
              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 meanings:
              -a      Automatically mark variables which are mod-
                      ified or created for export to the environ-
                      ment of subsequent commands.
              -b      Report  the status of terminated background
                      jobs immediately, rather  than  before  the
                      next  primary  prompt.   This  is effective
                      only when job control is enabled.
              -e      Exit immediately if a simple  command  (see
                      SHELL  GRAMMAR above) exits with a non-zero
                      status.  The shell does  not  exit  if  the
                      command  that  fails is part of an until or
                      while loop, part of an if  statement,  part
                      of  a  &&&&  or  |||| list, or if the command's
                      return value is being inverted via !!.
              -f      Disable pathname expansion.
              -h      Remember the location of commands  as  they
                      are  looked  up  for  execution.   This  is
                      enabled by default.
              -k      All arguments in  the  form  of  assignment



GNU                       1996 March 20                        14





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


                      statements  are  placed  in the environment
                      for a command, not just those that  precede
                      the command name.
              -m      Monitor  mode.   Job  control  is  enabled.
                      This option is on by default  for  interac-
                      tive shells on systems that support it (see
                      JOB CONTROL above).   Background  processes
                      run  in a separate process group and a line
                      containing their  exit  status  is  printed
                      upon their completion.
              -n      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.
              -o option-name
                      The option-name can be one of  the  follow-
                      ing:
                      allexport
                              Same as -a.
                      braceexpand
                              Same as -B.
                      emacs   Use  an  emacs-style  command  line
                              editing interface.  This is enabled
                              by default when the shell is inter-
                              active, unless the shell is started
                              with the --noediting option.
                      errexit Same as -e.
                      hashall Same as -h.
                      histexpand
                              Same as -H.
                      history Enable    command    history,    as
                              described  above   under   HISTORY.
                              This  option  is  on  by default in
                              interactive shells.
                      ignoreeof
                              The effect is as if the shell  com-
                              mand IGNOREEOF=10 had been executed
                              (see Shell Variables above).
                      keyword Same as -k.
                      monitor Same as -m.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      notify  Same as -b.
                      nounset Same as -u.
                      onecmd  Same as -t.
                      physical
                              Same as -P.
                      posix   Change the behavior of  bash  where
                              the  default operation differs from
                              the POSIX 1003.2 standard to  match
                              the standard.




GNU                       1996 March 20                        15





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


                      privileged
                              Same as -p.
                      verbose Same as -v.
                      vi      Use a vi-style command line editing
                              interface.
                      xtrace  Same as -x.
                      If -o is supplied with no option-name,  the
                      values  of the current options are printed.
                      If +o is supplied with  no  option-name,  a
                      series of set commands to recreate the cur-
                      rent option settings is  displayed  on  the
                      standard output.
              -p      Turn on privileged mode.  In this mode, the
                      $ENV and $BASH_ENV files are not processed,
                      shell  functions are not inherited from the
                      environment, and the SHELLOPTS 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 -p option is  not  sup-
                      plied,  these  actions  are  taken  and the
                      effective user id is set to the  real  user
                      id.   If  the  -p  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.
              -t      Exit  after  reading and executing one com-
                      mand.
              -u      Treat unset variables as an error when per-
                      forming  parameter 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.
              -v      Print shell input lines as they are read.
              -x      After  expanding  each simple command, dis-
                      play the expanded value of PS4, followed by
                      the command and its expanded arguments.
              -B      The  shell  performs  brace  expansion (see
                      Brace Expansion  above).   This  is  on  by
                      default.
              -C      If set, bash does not overwrite an existing
                      file with the >>,  >>&&,  and  <<>>  redirection
                      operators.   This  may  be  overridden when
                      creating output files by using the redirec-
                      tion operator >>|| instead of >>.
              -H      Enable !!  style history substitution.  This
                      option is on by default when the  shell  is
                      interactive.
              -P      If  set, the shell does not follow symbolic
                      links when executing commands  such  as  cd
                      that  change the current working directory.
                      It uses the  physical  directory  structure
                      instead.   By  default,  bash  follows  the



GNU                       1996 March 20                        16





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


                      logical chain of directories when  perform-
                      ing   commands  which  change  the  current
                      directory.
              ----      If no arguments follow  this  option,  then
                      the  positional parameters are unset.  Oth-
                      erwise, the positional parameters  are  set
                      to  the  args,  even  if some of them begin
                      with a --.
              --       Signal  the  end  of  options,  cause   all
                      remaining  args to be assigned to the posi-
                      tional parameters.  The -x and  -v  options
                      are  turned off.  If there are no args, the
                      positional 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  speci-
              fied  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 encountered.

       shift [_n]
              The positional parameters from _n+1 ... are  renamed
              to  $$11  ........  Parameters represented by the numbers
              $$## down to $$##-_n+1 are unset.  _n must be a non-nega-
              tive  number  less than or equal to $$##.  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.

       shopt [-pqsu] [-o] [optname ...]
              Toggle the values of variables controlling optional
              shell  behavior.   With  no options, or with the -p
              option, a list of  all  settable  options  is  dis-
              played,  with  an indication of whether or not each
              is set.  The -p option causes  output  to  be  dis-
              played  in  a  form  that  may  be reused as input.
              Other options have the following meanings:
              -s     Enable (set) each optname.
              -u     Disable (unset) each optname.
              -q     Suppresses normal output (quiet  mode);  the
                     return  status indicates whether the optname
                     is set or unset.  If multiple optname  argu-
                     ments  are  given with -q, the return status
                     is zero if all optnames  are  enabled;  non-
                     zero otherwise.
              -o     Restricts  the values of optname to be those
                     defined  for  the  -o  option  to  the   set
                     builtin.

              If  either  -s  or  -u  is  used  with  no  optname



GNU                       1996 March 20                        17





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              arguments, the display is limited to those  options
              which  are set or unset, respectively.  Unless oth-
              erwise  noted,  the  shopt  options  are   disabled
              (unset) by default.

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

              The list of shopt options is:

              cdable_vars
                      If  set, an argument to the cd builtin com-
                      mand that is not a directory is assumed  to
                      be  the  name  of a variable whose value is
                      the directory to change to.
              cdspell If set, minor errors in the spelling  of  a
                      directory component in a cd command will be
                      corrected.   The  errors  checked  for  are
                      transposed characters, a missing character,
                      and one character too many.  If  a  correc-
                      tion  is  found, the corrected file name is
                      printed, and the  command  proceeds.   This
                      option  is only used by interactive shells.
              checkhash
                      If set, bash checks that a command found in
                      the hash table exists before trying to exe-
                      cute it.  If a  hashed  command  no  longer
                      exists,  a normal path search is performed.
              checkwinsize
                      If set, bash checks the window  size  after
                      each command and, if necessary, updates the
                      values of LINES and COLUMNS.
              cmdhist If set, bash attempts to save all lines  of
                      a multiple-line command in the same history
                      entry.   This  allows  easy  re-editing  of
                      multi-line commands.
              dotglob If  set,  bash includes filenames beginning
                      with a  `.'  in  the  results  of  pathname
                      expansion.
              execfail
                      If  set,  a  non-interactive shell will not
                      exit if it cannot execute the  file  speci-
                      fied  as  an  argument  to the exec builtin
                      command.  An  interactive  shell  does  not
                      exit if exec fails.
              expand_aliases
                      If  set,  aliases are expanded as described
                      above  under  ALIASES.   This   option   is
                      enabled  by default for interactive shells.
              extglob If set, the extended pattern matching  fea-
                      tures described above under Pathname Expan-
                      sion are enabled.



GNU                       1996 March 20                        18





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              histappend
                      If set, the history list is appended to the
                      file  named  by  the  value of the HISTFILE
                      variable when the shell exits, rather  than
                      overwriting the file.
              histreedit
                      If  set, and readline is being used, a user
                      is  given  the  opportunity  to  re-edit  a
                      failed history substitution.
              histverify
                      If  set,  and  readline  is being used, the
                      results of  history  substitution  are  not
                      immediately  passed  to  the  shell parser.
                      Instead, the resulting line is loaded  into
                      the  readline editing buffer, allowing fur-
                      ther modification.
              hostcomplete
                      If set, and readline is  being  used,  bash
                      will attempt to perform hostname completion
                      when a word containing a @@  is  being  com-
                      pleted   (see   Completing  under  READLINE
                      above).  This is enabled by default.
              huponexit
                      If set, bash will send SIGHUP to  all  jobs
                      when an interactive login shell exits.
              interactive_comments
                      If  set,  allow  a word beginning with ## to
                      cause that word and all  remaining  charac-
                      ters  on  that  line  to  be  ignored in an
                      interactive  shell  (see  COMMENTS  above).
                      This option is enabled by default.
              lithist If  set, and the cmdhist option is enabled,
                      multi-line commands are saved to  the  his-
                      tory  with  embedded  newlines  rather than
                      using semicolon separators where  possible.
              mailwarn
                      If  set,  and  a file that bash is checking
                      for mail has been accessed since  the  last
                      time it was checked, the message ``The mail
                      in mailfile has been read'' is displayed.
              nocaseglob
                      If  set,  bash  matches  filenames   in   a
                      case-insensitive  fashion  when  performing
                      pathname expansion (see Pathname  Expansion
                      above).
              nullglob
                      If set, bash allows patterns which match no
                      files (see  Pathname  Expansion  above)  to
                      expand  to a null string, rather than them-
                      selves.
              promptvars
                      If set, prompt strings undergo variable and
                      parameter expansion after being expanded as
                      described in PROMPTING above.  This  option



GNU                       1996 March 20                        19





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


                      is enabled by default.
              restricted_shell
                      The shell sets this option if it is started
                      in restricted mode  (see  RESTRICTED  SHELL
                      below).   The  value  may  not  be changed.
                      This is not reset when  the  startup  files
                      are executed, allowing the startup files to
                      discover  whether  or  not   a   shell   is
                      restricted.
              shift_verbose
                      If  set,  the shift builtin prints an error
                      message when the shift  count  exceeds  the
                      number of positional parameters.
              sourcepath
                      If  set,  the  source  (..) builtin uses the
                      value of PATH to find  the  directory  con-
                      taining  the  file supplied as an argument.
                      This option is enabled by default.
       suspend [-f]
              Suspend  the  execution  of  this  shell  until  it
              receives  a SIGCONT signal.  The -f 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 -f is not  supplied,  or  if  job
              control is not enabled.
       test expr
       [[ expr ]]
              Return  a status of 0 or 1 depending on the evalua-
              tion of  the  conditional  expression  expr.   Each
              operator  and  operand must be a separate argument.
              Expressions are composed of the primaries described
              above under CONDITIONAL EXPRESSIONS.

              Expressions  may  be  combined  using the following
              operators, listed in  decreasing  order  of  prece-
              dence.
              !! expr True if expr is false.
              (( expr ))
                     Returns the value of expr.  This may be used
                     to override the normal precedence of  opera-
                     tors.
              expr1 -aa expr2
                     True if both expr1 and expr2 are true.
              expr1 -oo expr2
                     True if either expr1 or expr2 is true.

              test 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.



GNU                       1996 March 20                        20





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              2 arguments
                     If  the  first argument is !!, the expression
                     is true if and only if the  second  argument
                     is  null.   If  the first argument is one of
                     the unary conditional operators listed above
                     under  CONDITIONAL  EXPRESSIONS, the expres-
                     sion is true if the unary test is true.   If
                     the first argument is not a valid unary con-
                     ditional operator, the expression is  false.
              3 arguments
                     If  the second argument is one of the binary
                     conditional  operators  listed  above  under
                     CONDITIONAL  EXPRESSIONS,  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 argu-
                     ment.  Otherwise, the expression  is  false.
                     The  -a  and  -o  operators  are  considered
                     binary operators in this case.
              4 arguments
                     If the first argument is !!,  the  result  is
                     the  negation  of the three-argument expres-
                     sion composed of  the  remaining  arguments.
                     Otherwise,  the  expression  is  parsed  and
                     evaluated according to precedence using  the
                     rules listed above.
              5 or more arguments
                     The   expression  is  parsed  and  evaluated
                     according  to  precedence  using  the  rules
                     listed above.

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

       trap [-lp] [arg] [sigspec ...]
              The command arg is to be read and executed when the
              shell receives signal(s) sigspec.  If arg is absent
              or  --,  all  specified  signals  are reset to their
              original values (the values they had upon  entrance
              to  the shell).  If arg is the null string the sig-
              nal specified by each sigspec  is  ignored  by  the
              shell and by the commands it invokes.  If arg is -p
              then the trap commands associated with each sigspec
              are  displayed.  If no arguments are supplied or if
              only -p is given, trap prints the list of  commands
              associated  with  each signal number.  Each sigspec
              is either a signal name defined in <signal.h>, or a
              signal  number.   If  a  sigspec  is  EXIT  (0) the



GNU                       1996 March 20                        21





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              command arg is executed on exit from the shell.  If
              a  sigspec  is  DEBUG,  the command arg is executed
              after  every  simple  command  (see  SHELL  GRAMMAR
              above).   The -l option causes the shell to print a
              list of signal names and their  corresponding  num-
              bers.  Signals ignored upon entry to the shell can-
              not be trapped or reset.  Trapped signals are reset
              to their original values in a child process when it
              is created.  The return  status  is  false  if  any
              sigspec is invalid; otherwise trap returns true.

       type [-atp] name [name ...]
              With  no  options,  indicate how each name would be
              interpreted if used as a command name.  If  the  -t
              option  is  used, type prints a string which is one
              of alias, keyword, function, builtin,  or  file  if
              name  is  an  alias, shell reserved word, function,
              builtin, or disk file, respectively.  If  the  name
              is  not found, then nothing is printed, and an exit
              status of false is returned.  If the -p  option  is
              used, type either returns the name of the disk file
              that would be executed if name were specified as  a
              command  name, or nothing if type -t name would not
              return file.  If a command is hashed, -p prints the
              hashed value, not necessarily the file that appears
              first in PATH.  If the  -a  option  is  used,  type
              prints all of the places that contain an executable
              named name.  This includes aliases  and  functions,
              if and only if the -p option is not also used.  The
              table of hashed  commands  is  not  consulted  when
              using  -a.   type  returns true if any of the argu-
              ments are found, false if none are found.

       ulimit [-SHacdflmnpstuv [limit]]
              Provides control over the  resources  available  to
              the  shell  and to processes started by it, on sys-
              tems that allow such control.  The value  of  limit
              can  be  a  number  in  the  unit specified for the
              resource, or the value unlimited.  The  -H  and  -S
              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  -H  nor -S is specified, both the soft and
              hard limits are set.  If limit is omitted, the cur-
              rent  value  of  the  soft limit of the resource is
              printed, unless the -H 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 follows:
              -a     All current limits are reported
              -c     The maximum size of core files created
              -d     The maximum size of a process's data segment
              -f     The maximum size of  files  created  by  the



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BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


                     shell
              -l     The  maximum  size  that  may be locked into
                     memory
              -m     The maximum resident set size
              -n     The maximum number of open file  descriptors
                     (most  systems do not allow this value to be
                     set)
              -p     The pipe size in 512-byte blocks  (this  may
                     not be set)
              -s     The maximum stack size
              -t     The maximum amount of cpu time in seconds
              -u     The maximum number of processes available to
                     a single user
              -v     The maximum amount of virtual memory  avail-
                     able to the shell

              If limit is given, it is the new value of the spec-
              ified resource (the -a option is display only).  If
              no option is given, then -f is assumed.  Values are
              in 1024-byte increments, except for -t, which is in
              seconds,  -p, which is in units of 512-byte blocks,
              and -n and -u,  which  are  unscaled  values.   The
              return  status  is  0  unless  an invalid option is
              encountered,  a  non-numeric  argument  other  than
              unlimited  is supplied as limit, or an error occurs
              while setting a new limit.

       umask [-p] [-S] [mode]
              The user file-creation mask is  set  to  mode.   If
              mode  begins  with a digit, it is interpreted as an
              octal number; otherwise it is interpreted as a sym-
              bolic   mode  mask  similar  to  that  accepted  by
              chmod(1).  If mode is omitted, or if the -S  option
              is  supplied,  the  current  value  of  the mask is
              printed.  The -S  option  causes  the  mask  to  be
              printed  in symbolic form; the default output is an
              octal number.  If the -p option  is  supplied,  and
              mode  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 mode argu-
              ment was supplied, and false otherwise.

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

       unset [-fv] [name ...]
              For each name, remove the corresponding variable or
              function.  If no options are supplied,  or  the  -v
              option  is given, each name refers to a shell vari-
              able.  Read-only variables may not be unset.  If -f
              is  specifed, each name refers to a shell function,



GNU                       1996 March 20                        23





BASH_BUILTINS(1)                                 BASH_BUILTINS(1)


              and the function definition is removed.  Each unset
              variable  or  function is removed from the environ-
              ment passed to subsequent commands.  If any of RAN-
              DOM,  SECONDS,  LINENO,  HISTCMD,  or  DIRSTACK are
              unset, they lose their special properties, even  if
              they  are  subsequently  reset.  The exit status is
              true unless a name does not exist or is readonly.

       wait [_n]
              Wait for the specified process and return its  ter-
              mination  status.   _n  may be a process ID or a job
              specification; if a job spec  is  given,  all  pro-
              cesses 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.  Otherwise, the return status
              is the exit status  of  the  last  process  or  job
              waited for.

SEE ALSO
       bash(1), sh(1)



































GNU                       1996 March 20                        24


