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BASH-BUILTINS(7)					      BASH-BUILTINS(7)



NAME
       bash-builtins - bash built-in commands, see bash(1)

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

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.   For  example,  the  :, true, false, and test builtins do not
       accept options.
       : [arguments]
	      No effect; the command does nothing beyond  expanding  arguments
	      and  performing any specified redirections.  A zero exit code is
	      returned.

	.  filename [arguments]
       source filename [arguments]
	      Read and execute commands from filename  in  the	current  shell
	      environment  and return the exit status of the last command exe
	      cuted from filename.  If filename does not contain a slash, file
	      names  in  PATH  are used to find the directory containing file
	      name.  The file searched for in PATH  need  not  be  executable.
	      When  bash  is  not  in  posix  mode,  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  posi
	      tional  parameters  when	filename  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 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  sup
	      plied,  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  each  suspended  job jobspec in the background, as if it
	      had been started with &.	If jobspec is not present, the shells
	      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,	any  specified	jobspec  was  not found or was started
	      without job control.

       bind [-m keymap] [-lpsvPSV]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] -x keyseq:shell-command
       bind [-m keymap] keyseq:function-name
       bind readline-command
	      Display current readline key and function bindings, bind	a  key
	      sequence	to  a  readline  function  or macro, or set a readline
	      variable.  Each non-option argument is a	command  as  it  would
	      appear  in  .inputrc, 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:
	      -m keymap
		     Use keymap as the keymap to be affected by the subsequent
		     bindings.	Acceptable keymap names are emacs, emacs-stan
		     dard,  emacs-meta,  emacs-ctlx,  vi, vi-move, 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.
	      -x keyseq:shell-command
		     Cause shell-command to be	executed  whenever  keyseq  is
		     entered.

	      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 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 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  func
	      tionality 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 [-L|-P] [dir]
	      Change  the  current directory to dir.  The variable HOME is the
	      default dir.  The variable CDPATH defines the  search  path  for
	      the  directory  containing  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 fol
	      lowed.  An argument of - is equivalent to $OLDPWD.   If  a  non-
	      empty  directory	name from CDPATH 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.

       caller [expr]
	      Returns the context of any active subroutine call (a shell func
	      tion or a  script  executed  with  the  .  or  source  builtins.
	      Without  expr,  caller displays the line number and source file
	      name of the current subroutine call.  If a non-negative  integer
	      is supplied as expr, caller displays the line number, subroutine
	      name, and source file corresponding to that position in the cur
	      rent  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
	      subroutine call or expr does not correspond to a valid  position
	      in the call stack.

       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 indicating the command or file name
	      used to invoke command 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 can
	      not be found, the exit status is 127.  Otherwise, the exit  sta
	      tus of the command builtin is the exit status of command.

       compgen [option] [word]
	      Generate	possible  completion matches for word according to the
	      options, which may  be  any  option  accepted  by  the  complete
	      builtin  with  the exception of -p and -r, and write the matches
	      to the standard output.  When using the -F or  -C  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 word is speci
	      fied, only those completions matching word will be displayed.

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

       complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat]  [-W
       wordlist] [-P prefix] [-S suffix]
	      [-X filterpat] [-F function] [-C command] name [name ...]
       complete -pr [name ...]
	      Specify how arguments to each name should be completed.  If  the
	      -p  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 -r option removes a completion spec
	      ification for each name, or, if no names are supplied, all  com
	      pletion specifications.

	      The  process  of	applying  these completion specifications when
	      word completion is  attempted  is  described  above  under  Pro
	      grammable Completion.

	      Other  options,  if specified, have the following meanings.  The
	      arguments to the -G, -W, and -X options (and, if necessary,  the
	      -P  and -S options) should be quoted to protect them from expan
	      sion before the complete builtin is invoked.
	      -o comp-option
		      The comp-option controls several aspects	of  the  comp
		      specs  behavior beyond the simple generation of comple
		      tions.  comp-option may be one of:
		      bashdefault
			      Perform the rest of the default bash completions
			      if the compspec generates no matches.
		      default Use  readlines  default  filename completion if
			      the compspec generates no matches.
		      dirnames
			      Perform directory name completion if  the  comp
			      spec generates no matches.
		      filenames
			      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.
		      nospace Tell   readline  not  to	append	a  space  (the
			      default) to words completed at the  end  of  the
			      line.
		      plusdirs
			      After  any  matches  defined by the compspec are
			      generated,   directory   name   completion    is
			      attempted  and  any  matches  are  added	to the
			      results of the other actions.
	      -A action
		      The action may be one of the  following  to  generate  a
		      list of possible completions:
		      alias   Alias names.  May also be specified as -a.
		      arrayvar
			      Array variable names.
		      binding Readline key binding names.
		      builtin Names  of  shell	builtin commands.  May also be
			      specified as -b.
		      command Command names.  May also be specified as -c.
		      directory
			      Directory names.	May also be specified as -d.
		      disabled
			      Names of disabled shell builtins.
		      enabled Names of enabled shell builtins.
		      export  Names of exported shell variables.  May also  be
			      specified as -e.
		      file    File names.  May also be specified as -f.
		      function
			      Names of shell functions.
		      group   Group names.  May also be specified as -g.
		      helptopic
			      Help topics as accepted by the help builtin.
		      hostname
			      Hostnames,  as  taken from the file specified by
			      the HOSTFILE shell variable.
		      job     Job names, if job control is active.   May  also
			      be specified as -j.
		      keyword Shell  reserved words.  May also be specified as
			      -k.
		      running Names of running jobs, if job control is active.
		      service Service names.  May also be specified as -s.
		      setopt  Valid  arguments	for  the  -o option to the set
			      builtin.
		      shopt   Shell option names  as  accepted	by  the  shopt
			      builtin.
		      signal  Signal names.
		      stopped Names of stopped jobs, if job control is active.
		      user    User names.  May also be specified as -u.
		      variable
			      Names of all shell variables.  May also be spec
			      ified as -v.
	      -G globpat
		      The  filename  expansion	pattern globpat is expanded to
		      generate the possible completions.
	      -W wordlist
		      The wordlist is split using the characters  in  the  IFS
		      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.
	      -C command
		      command is executed in a subshell environment,  and  its
		      output is used as the possible completions.
	      -F function
		      The  shell  function function is executed in the current
		      shell environment.  When it finishes, the possible  com
		      pletions	are  retrieved from the value of the COMPREPLY
		      array variable.
	      -X filterpat
		      filterpat is a pattern as used for  filename  expansion.
		      It is applied to the list of possible completions gener
		      ated by the preceding options and  arguments,  and  each
		      completion  matching filterpat is removed from the list.
		      A leading ! in filterpat negates the  pattern;  in  this
		      case,  any completion not matching filterpat is removed.
	      -P prefix
		      prefix is added at the beginning of each	possible  com
		      pletion after all other options have been applied.
	      -S suffix
		      suffix 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 -p or -r is supplied without a name argu
	      ment, an attempt is made to remove  a  completion  specification
	      for a name for which no specification exists, or an error occurs
	      adding a completion specification.

       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.  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 [-afFirtx] [-p] [name[=value] ...]
       typeset [-afFirtx] [-p] [name[=value] ...]
	      Declare  variables and/or give them attributes.  If no names are
	      given then display the values of variables.  The -p option  will
	      display  the  attributes	and  values  of each name.  When -p is
	      used, additional options are ignored.  The  -F  option  inhibits
	      the  display of function definitions; only the function name and
	      attributes are printed.  If the extdebug shell option is enabled
	      using  shopt,  the  source  file	name and line number where the
	      function is defined  are	displayed  as  well.   The  -F	option
	      implies  -f.  The following options can be used to restrict out
	      put to variables with the specified attribute or to  give  vari
	      ables 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 evalua
		     tion (see ARITHMETIC EVALUATION ) 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.
	      -t     Give each name the  trace	attribute.   Traced  functions
		     inherit  the  DEBUG  and  RETURN  traps  from the calling
		     shell.  The trace attribute has no  special  meaning  for
		     variables.
	      -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 vari
	      able.  When used in a function, makes each name local,  as  with
	      the  local  command.   If a variable name is followed by =value,
	      the value of the variable is set to value.  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 Arrays above), one of the names 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 -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.
	      +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  listing	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, 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.

       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 supplied, the  -a	option
	      means  to  remove or mark all jobs; the -r option without a job
	      spec 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, interpreta
	      tion of the following backslash-escaped characters  is  enabled.
	      The  -E option disables the interpretation of these escape char
	      acters, even on systems where they are interpreted  by  default.
	      The  xpg_echo  shell option may be used to dynamically determine
	      whether or not echo expands these escape characters 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
	      \v     vertical tab
	      \\     backslash
	      \0nnn  the eight-bit character whose value is  the  octal  value
		     nnn (zero to three octal digits)
	      \nnn   the  eight-bit  character	whose value is the octal value
		     nnn (one to three octal digits)
	      \xHH   the eight-bit character whose value  is  the  hexadecimal
		     value HH (one or two hex digits)

       enable [-adnps] [-f filename] [name ...]
	      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  -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 support 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 supplied,
	      a list of shell builtins is printed.  With no other option argu
	      ments,  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 indi
	      cation 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 an error loading a new builtin from a shared object.

       eval [arg ...]
	      The  args  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 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 supplied, the shell places a dash at the begin
	      ning of 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 can
	      not be executed.	If command 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  envi
	      ronment  of subsequently executed commands.  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 each name.  If a variable
	      name is followed by =word, the value of the variable is  set  to
	      word.   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 func
	      tion.

       fc [-e ename] [-nlr] [first] [last]
       fc -s [pat=rep] [cmd]
	      Fix Command.  In the first form, a range of commands from  first
	      to  last	is selected from the history 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 history
	      list, where a negative number is used as an offset from the cur
	      rent command number).  If last is not specified it is set to the
	      current command for listing (so that fc -l  -10  prints  the
	      last 10 commands) and to first otherwise.  If first is not spec
	      ified 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.	Other
	      wise, the editor 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 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 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-exe
	      cuted, unless cmd does not specify  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 shells 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 spec
	      ify a valid job or jobspec specifies  a  job  that  was  started
	      without job control.

       getopts optstring name [args]
	      getopts  is used by shell procedures to parse positional parame
	      ters.  optstring 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,  getopts
	      places  the next option in the shell variable name, initializing
	      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  automati
	      cally;  it  must	be  manually  reset  between multiple calls to
	      getopts within the same shell invocation if a new set of parame
	      ters 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.

	      getopts can report errors in two ways.  If the  first  character
	      of  optstring  is  a  colon, silent error reporting is used.  In
	      normal operation diagnostic 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  dis
	      played, even if the first character of optstring 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 [-lr] [-p filename] [-dt] [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 locations.  The -d option
	      causes the shell to forget the remembered location of each name.
	      If  the  -t  option is supplied, the full pathname to which each
	      name corresponds is printed.  If	multiple  name	arguments  are
	      supplied	with  -t,  the	name is printed before the hashed full
	      pathname.  The -l option causes output to be displayed in a for
	      mat  that may be reused as input.  If no arguments are given, or
	      if only -l is supplied, information about remembered commands is
	      printed.	 The  return status is true unless a name is not found
	      or an invalid option is supplied.

       help [-s] [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 -s option restricts the information
	      displayed to a short usage synopsis.  The  return  status  is  0
	      unless no command matches pattern.

       history [n]
       history -c
       history -d offset
       history -anrw [filename]
       history -p arg [arg ...]
       history -s arg [arg ...]
	      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 HISTTIME
	      FORMAT is set and not null, it is used as a  format  string  for
	      strftime(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 filename is
	      supplied, it is used as the name of the history  file;  if  not,
	      the  value  of HISTFILE is used.	Options, if supplied, have the
	      following meanings:
	      -c     Clear the history list by deleting all the entries.
	      -d offset
		     Delete the history entry at position offset.
	      -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 history 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,  overwrit
		     ing the history files contents.
	      -p     Perform  history  substitution  on the following args and
		     display the result on  the  standard  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	single	entry.
		     The  last	command  in the history list is removed before
		     the args are added.

	      If the HISTTIMEFORMAT 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 offset is supplied as an argument to -d, or the  history
	      expansion supplied as an argument to -p fails.

       jobs [-lnprs] [ jobspec ... ]
       jobs -x command [ args ... ]
	      The first form lists the active jobs.  The options have the fol
	      lowing meanings:
	      -l     List process IDs in addition to the normal information.
	      -p     List only the process  ID	of  the  jobs  process	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 information 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 corresponding  process  group  ID,  and
	      executes command passing it args, returning its exit status.

       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  case-insensitive
	      signal  name such as SIGKILL (with or without the SIG prefix) or
	      a signal number; signum is a signal number.  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
	      status of a process terminated by a signal.  kill  returns  true
	      if  at  least  one  signal was successfully sent, or false if an
	      error occurs or an invalid option is encountered.

       let arg [arg ...]
	      Each arg is an arithmetic expression to be evaluated (see ARITH
	      METIC  EVALUATION).  If the last arg evaluates to 0, let returns
	      1; 0 is returned otherwise.

       local [option] [name[=value] ...]
	      For each argument, a local variable named name is  created,  and
	      assigned	value.	 The option can be any of the options accepted
	      by declare.  When local is used within a function, it causes the
	      variable	name  to have a visible scope restricted to that func
	      tion 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 function.  The return status is 0 unless
	      local  is  used outside a function, an invalid name is supplied,
	      or name is a readonly variable.

       logout Exit a login shell.

       popd [-n] [+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 follow
	      ing meanings:
	      +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.
	      -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 performed as well,
	      and the return status is 0.  popd 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.

       printf [-v var] format [arguments]
	      Write  the  formatted arguments to the standard output 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 output, and for
	      mat specifications, each of which causes printing  of  the  next
	      successive argument.  In addition to the standard printf(1) for
	      mats, %b causes printf to expand backslash escape  sequences  in
	      the  corresponding  argument  (except that \c terminates output,
	      backslashes in \, \", and \? are not removed, and octal escapes
	      beginning  with \0 may contain up to four digits), and %q causes
	      printf to output the corresponding argument in a format that can
	      be reused as shell input.

	      The  -v  option causes the output to be assigned to the variable
	      var rather than being printed to the standard output.

	      The format is reused as necessary to consume all	of  the  argu
	      ments.  If the format requires more arguments 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.

       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 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 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 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 pathname of the  current  working  directory.
	      The pathname printed contains no symbolic 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, 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.

       read [-ers] [-u fd] [-t timeout] [-a aname] [-p prompt] [-n nchars] [-d
       delim] [name ...]
	      One line is read from the  standard  input,  or  from  the  file
	      descriptor  fd supplied as an argument to the -u option, and the
	      first word is assigned to the first name, the second word to the
	      second  name, and so on, with leftover words and their interven
	      ing separators assigned to the last name.  If  there  are  fewer
	      words read from the input stream 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 supplied, have the fol
	      lowing meanings:
	      -a aname
		     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.
	      -d delim
		     The  first  character  of	delim is used to terminate the
		     input line, rather than newline.
	      -e     If the standard input is coming from a terminal, readline
		     (see READLINE above) is used to obtain the line.
	      -n nchars
		     read  returns after reading nchars characters rather than
		     waiting for a complete line of input.
	      -p prompt
		     Display prompt 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.
	      -r     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.
	      -s     Silent mode.  If input is coming from a terminal, charac
		     ters are not echoed.
	      -t timeout
		     Cause read to time out and return failure if  a  complete
		     line  of  input is not read within timeout seconds.  This
		     option has no effect if read is not  reading  input  from
		     the terminal or a pipe.
	      -u fd  Read input from file descriptor fd.

	      If no names are supplied, the line read is assigned to the vari
	      able REPLY.  The return code  is	zero,  unless  end-of-file  is
	      encountered,  read  times  out, or an invalid file descriptor is
	      supplied as the argument to -u.

       readonly [-apf] [name[=word] ...]
	      The given names are marked readonly; the values of  these  names
	      may  not	be changed by subsequent 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 displayed in a format that may be reused as	input.
	      If  a variable name is followed by =word, the value of the vari
	      able is set to word.  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 func
	      tion.

       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 function 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  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 RETURN trap is
	      executed before execution resumes after the function or  script.

       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 for setting or
	      resetting the currently-set variables.  Read-only variables can
	      not be reset.  In posix mode, only shell variables  are  listed.
	      The  output  is  sorted  according  to the current locale.  When
	      options are specified, they set or unset shell attributes.   Any
	      arguments  remaining after the options are processed are treated
	      as values for the positional parameters  and  are  assigned,  in
	      order, to $1, $2, ...  $n.  Options, if specified, have the fol
	      lowing meanings:
	      -a      Automatically mark variables  and  functions  which  are
		      modified	or  created  for  export to the environment of
		      subsequent commands.
	      -b      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.
	      -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  the  command
		      list  immediately  following  a  while or until keyword,
		      part of the test in an if statement, part of a && or
		      list, or if the commands return value is being inverted
		      via !.  A trap on ERR, if set, is  executed  before  the
		      shell exits.
	      -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  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  interactive shells on systems that
		      support it (see JOB  CONTROL  above).   Background  pro
		      cesses  run  in a separate process group and a line con
		      taining their exit status is printed upon their  comple
		      tion.
	      -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 following:
		      allexport
			      Same as -a.
		      braceexpand
			      Same as -B.
		      emacs   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 --noediting option.
		      errtrace
			      Same as -E.
		      functrace
			      Same as -T.
		      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 inter
			      active shells.
		      ignoreeof
			      The  effect  is  as   if	 the   shell   command
			      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.  nolog Currently ignored.
		      notify  Same as -b.
		      nounset Same as -u.
		      onecmd  Same as -t.
		      physical
			      Same as -P.
		      pipefail
			      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.
		      posix   Change the behavior of bash  where  the  default
			      operation differs from the POSIX 1003.2 standard
			      to match the standard (posix mode).
		      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
		      current  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 supplied, 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 command.
	      -u      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.
	      -v      Print shell input lines as they are read.
	      -x      After expanding each simple command, for	command,  case
		      command, select command, or arithmetic for command, dis
		      play the expanded value of PS4, followed by the  command
		      and its expanded arguments or associated word list.
	      -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 redi
		      rection operator >| instead of >.
	      -E      If set, any trap on ERR is inherited by shell functions,
		      command substitutions, and commands executed in  a  sub
		      shell  environment.  The ERR trap is normally not inher
		      ited in such cases.
	      -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 logical
		      chain  of  directories  when  performing	commands which
		      change the current directory.
	      -T      If set, any traps on DEBUG and RETURN are  inherited  by
		      shell  functions,  command  substitutions,  and commands
		      executed in  a  subshell	environment.   The  DEBUG  and
		      RETURN traps are normally not inherited in such cases.
	      --      If  no arguments follow this option, then the positional
		      parameters are unset.  Otherwise, the positional parame
		      ters  are  set  to  the args, even if some of them begin
		      with a -.
	      -       Signal the end of options, cause all remaining  args  to
		      be assigned to the positional parameters.  The -x and -v
		      options are turned off.  If there are no args, 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.

       shift [n]
	      The positional parameters from n+1 ... are renamed  to  $1  ....
	      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.

       shopt [-pqsu] [-o] [optname ...]
	      Toggle the values of variables controlling optional shell behav
	      ior.  With no options, or with the -p option, a list of all set
	      table options is displayed, with an indication of whether or not
	      each  is	set.  The -p option causes output to be displayed in a
	      form that may be reused as input.  Other options have  the  fol
	      lowing 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 multi
		     ple  optname arguments are given with -q, the return sta
		     tus is zero if all optnames are enabled; non-zero	other
		     wise.
	      -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 arguments,  the  dis
	      play is limited to those options which are set or unset, respec
	      tively.  Unless otherwise 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  command  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 com
		      ponent  in  a  cd 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.
	      checkhash
		      If set, bash 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.
	      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 can
		      not  execute  the  file  specified 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 interac
		      tive shells.
	      extdebug
		      If  set,	behavior  intended  for  use  by  debuggers is
		      enabled:
		      1.     The -F option to the declare builtin displays the
			     source file name and line number corresponding to
			     each function name supplied as an argument.
		      2.     If the command run by the DEBUG  trap  returns  a
			     non-zero  value,  the next command is skipped and
			     not executed.
		      3.     If the command run by the DEBUG  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 source builtins), a call to
			     return is simulated.
		      4.     BASH_ARGC and BASH_ARGV are updated as  described
			     in their descriptions above.
		      5.     Function  tracing	is enabled:  command substitu
			     tion, shell functions, and subshells invoked with
			     ( command ) inherit the DEBUG and RETURN traps.
		      6.     Error  tracing is enabled:  command substitution,
			     shell functions, and  subshells  invoked  with  (
			     command ) inherit the ERROR trap.
	      extglob If set, the extended pattern matching features described
		      above under Pathname Expansion are enabled.
	      extquote
		      If set, $string and  $"string"  quoting  is  performed
		      within   ${parameter}   expansions  enclosed  in	double
		      quotes.  This option is enabled by default.
	      failglob
		      If set, patterns which fail to  match  filenames	during
		      pathname expansion result in an expansion error.
	      force_fignore
		      If  set,	the  suffixes  specified  by the FIGNORE shell
		      variable cause words to be ignored when performing  word
		      completion even if the ignored words are the only possi
		      ble  completions.   See  SHELL  VARIABLES  above	for  a
		      description  of  FIGNORE.   This	option	is  enabled by
		      default.
	      gnu_errfmt
		      If set, shell error messages are written in the standard
		      GNU error message format.
	      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  his
		      tory  substitution  are  not  immediately  passed to the
		      shell parser.  Instead, the  resulting  line  is	loaded
		      into the readline editing buffer, allowing further modi
		      fication.
	      hostcomplete
		      If set, and readline is being used, bash will attempt to
		      perform  hostname  completion when a word containing a @
		      is  being  completed  (see  Completing  under   READLINE
		      above).  This is enabled by default.
	      huponexit
		      If set, bash will send SIGHUP to all jobs when an inter
		      active login shell exits.
	      interactive_comments
		      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  COMMENTS	above).   This
		      option is enabled by default.
	      lithist If  set,	and  the cmdhist option is enabled, multi-line
		      commands are saved to the history with embedded newlines
		      rather than using semicolon separators where possible.
	      login_shell
		      The  shell  sets this option if it is started as a login
		      shell (see INVOCATION above).   The  value  may  not  be
		      changed.
	      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 dis
		      played.
	      no_empty_cmd_completion
		      If set, and  readline  is  being	used,  bash  will  not
		      attempt to search the PATH for possible completions when
		      completion is attempted on an empty line.
	      nocaseglob
		      If set, bash matches  filenames  in  a  case-insensitive
		      fashion when performing pathname expansion (see Pathname
		      Expansion above).
	      nocasematch
		      If set, bash  matches  patterns  in  a  case-insensitive
		      fashion when performing matching while executing case or
		      [[ conditional commands.
	      nullglob
		      If set, bash allows patterns which match no  files  (see
		      Pathname	Expansion  above)  to expand to a null string,
		      rather than themselves.
	      progcomp
		      If set, the programmable completion facilities (see Pro
		      grammable Completion above) are enabled.	This option is
		      enabled by default.
	      promptvars
		      If set, prompt strings undergo parameter expansion, com
		      mand   substitution,  arithmetic	expansion,  and  quote
		      removal after being expanded as described  in  PROMPTING
		      above.  This option 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  dis
		      cover 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 parame
		      ters.
	      sourcepath
		      If set, the source (.) builtin uses the value of PATH to
		      find the directory containing the file  supplied	as  an
		      argument.  This option is enabled by default.
	      xpg_echo
		      If   set,  the  echo  builtin  expands  backslash-escape
		      sequences 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  evaluation  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.  test does not
	      accept any options, nor does it accept and ignore an argument of
	      -- as signifying the end of options.

	      Expressions  may	be  combined  using  the  following operators,
	      listed in decreasing order of precedence.
	      ! expr True if expr is false.
	      ( expr )
		     Returns the value of expr.  This may be used to  override
		     the normal precedence of operators.
	      expr1 -a expr2
		     True if both expr1 and expr2 are true.
	      expr1 -o 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.
	      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 CONDITIONAL EXPRESSIONS,  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 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  argument.	 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 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.

       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 (and  there  is  a
	      single  sigspec)	or  -,	each  specified signal is reset to its
	      original disposition (the value it  had  upon  entrance  to  the
	      shell).	If arg is the null string the signal specified by each
	      sigspec is ignored by the shell and by the commands it  invokes.
	      If  arg  is  not present and -p has been supplied, 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.   The  -l	option
	      causes  the shell to print a list of signal names and their cor
	      responding numbers.   Each  sigspec  is  either  a  signal  name
	      defined  in  ,	or  a signal number.  Signal names are
	      case insensitive and the SIG prefix is optional.	If  a  sigspec
	      is  EXIT (0) the command arg is executed on exit from the shell.
	      If a sigspec is DEBUG, the command arg is executed before  every
	      simple command, for command, case command, select command, every
	      arithmetic for command, and before the first command executes in
	      a  shell	function  (see	SHELL  GRAMMAR	above).   Refer to the
	      description of the extdebug option  to  the  shopt  builtin  for
	      details  of  its effect on the DEBUG trap.  If a sigspec is ERR,
	      the command arg is executed whenever  a  simple  command	has  a
	      non-zero	exit status, subject to the following conditions.  The
	      ERR trap is not executed if the failed command is  part  of  the
	      command  list  immediately  following  a while or until keyword,
	      part of the test in an if statement, part of a && or  list, or
	      if  the  commands  return value is being inverted via !.	These
	      are the same conditions obeyed by  the  errexit  option.	 If  a
	      sigspec is RETURN, the command arg is executed each time a shell
	      function or a script executed with the . or source 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	sigspec  is  invalid;  otherwise  trap
	      returns true.

       type [-aftpP] 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 speci
	      fied as a command name, or nothing if type -t name would not
	      return file.  The -P option forces a PATH search for each  name,
	      even if type -t name would not return file.  If a command is
	      hashed, -p and -P print 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.  The -f option suppresses shell func
	      tion lookup, as with the command builtin.  type returns true  if
	      any of the arguments are found, false if none are found.

       ulimit [-SHacdefilmnpqrstuvx [limit]]
	      Provides	control  over the resources available to the shell and
	      to processes started by it, on systems that allow such  control.
	      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.  The value of limit can be a number in
	      the unit specified for the resource or one of the special values
	      hard,  soft,  or	unlimited,  which  stand  for the current hard
	      limit, the current soft limit, and no limit,  respectively.   If
	      limit  is  omitted,  the	current 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 fol
	      lows:
	      -a     All current limits are reported
	      -c     The maximum size of core files created
	      -d     The maximum size of a processs data segment
	      -e     The maximum scheduling priority (nice)
	      -f     The maximum size of files created by the shell
	      -i     The maximum number of pending signals
	      -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)
	      -q     The maximum number of bytes in POSIX message queues
	      -r     The maximum rt priority
	      -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 available to the
		     shell
	      -x     The maximum number of file locks

	      If limit is given, it is the new value of the specified 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 or argument is supplied, 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 symbolic mode mask similar to that accepted  by
	      chmod(1).   If mode is omitted, the current value of the mask is
	      printed.	The -S option causes the mask to be  printed  in  sym
	      bolic  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  argument	was  supplied,
	      and false otherwise.

       unalias [-a] [name ...]
	      Remove  each  name  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  variable.	Read-only variables may not be
	      unset.  If -f is specified, each name refers to  a  shell  func
	      tion,  and the function definition is removed.  Each unset vari
	      able or function is removed from the environment passed to  sub
	      sequent  commands.   If any of RANDOM, SECONDS, LINENO, HISTCMD,
	      FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their special
	      properties,  even if they are subsequently reset.  The exit sta
	      tus is true unless a name is readonly.

       wait [n ...]
	      Wait for each specified process and return its termination  sta
	      tus.   Each  n  may be a process ID or a job specification; if a
	      job spec is given, all processes	in  that  jobs	pipeline  are
	      waited  for.  If n is not given, all currently active child pro
	      cesses 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 Bash-2.05a			2001 October 29 	      BASH-BUILTINS(7)




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