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BASH_BUILTINS(1)								 BASH_BUILTINS(1)

NAME
       bash,  :,  .,  [, alias, bg, bind, break, builtin, caller, cd, command, compgen, complete,
       compopt, continue, declare, dirs, disown, echo, enable, eval, exec, exit,  export,  false,
       fc,  fg,  getopts,  hash,  help,  history,  jobs, kill, let, local, logout, mapfile, popd,
       printf, pushd, pwd, read, readonly, return, set,  shift,  shopt,  source,  suspend,  test,
       times, trap, true, type, typeset, ulimit, umask, unalias, unset, wait - bash built-in com-
       mands, 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.  The :, true, false,
       and test builtins do not accept options and do not treat -- specially.  The exit,  logout,
       break,  continue,  let,	and  shift builtins accept and process arguments beginning with -
       without requiring --.  Other builtins that accept  arguments  but  are  not  specified  as
       accepting  options  interpret arguments beginning with - as invalid options and require --
       to prevent this interpretation.
       : [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 executed 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 positional 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 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 each suspended job jobspec in the background, as if it had been started with
	      &.   If  jobspec is 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,  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  read-
	      line  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 sup-
	      plied, have the following meanings:
	      -m keymap
		     Use keymap as the keymap to be affected by the subsequent bindings.  Accept-
		     able  keymap  names  are  emacs, emacs-standard, 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.
	      -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.
	      -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.
	      -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.   When
		     shell-command  is executed, the shell sets the READLINE_LINE variable to the
		     contents of the readline line buffer and the READLINE_POINT variable to  the
		     current  location	of  the insertion point.  If the executed command changes
		     the value of READLINE_LINE or  READLINE_POINT,  those  new  values  will  be
		     reflected in the editing state.

	      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 n is not greater than or
	      equal to 1.

       builtin shell-builtin [arguments]
	      Execute the specified shell builtin, passing it arguments, and return its exit sta-
	      tus.   This  is  useful  when defining a function whose name is the same as a shell
	      builtin, retaining the functionality 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.

       caller [expr]
	      Returns the context of any active subroutine call (a shell  function  or	a  script
	      executed	with  the  . or source builtins).  Without expr, caller displays the line
	      number and source filename of the current subroutine call.  If a non-negative inte-
	      ger  is  supplied  as  expr,  caller displays the line number, subroutine name, and
	      source file corresponding to that position in the  current  execution  call  stack.
	      This  extra information may be used, for example, to print a stack trace.  The cur-
	      rent 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.

       cd [-L|[-P [-e]]] [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.  Alterna-
	      tive 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 direc-
	      tory 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.  If the
	      -e option is supplied with -P, and the current working directory cannot be success-
	      fully  determined after a successful directory change, cd will return an unsuccess-
	      ful status.  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 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  guaran-
	      teed  to find all of the standard utilities.  If either the -V or -v option is sup-
	      plied, 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 sup-
	      plied 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 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 avail-
	      able, will not have useful values.

	      The  matches  will  be  generated in the same way as if the programmable completion
	      code had generated them directly from a  completion  specification  with	the  same
	      flags.   If  word  is  specified, only those completions matching word will be dis-
	      played.

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

       complete [-abcdefgjksuv] [-o comp-option] [-DE] [-A action] [-G globpat] [-W wordlist] [-F
       function] [-C command]
	      [-X filterpat] [-P prefix] [-S suffix] name [name ...]
       complete -pr [-DE] [name ...]
	      Specify how arguments to each name should be completed.  If the -p option  is  sup-
	      plied,  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  specification  for each name, or, if no names are supplied, all comple-
	      tion specifications.  The -D  option  indicates  that  the  remaining  options  and
	      actions  should  apply  to  the ``default'' command completion; that is, completion
	      attempted on a command for which no completion has previously been defined.  The -E
	      option  indicates  that the remaining options and actions should apply to ``empty''
	      command completion; that is, completion attempted on a blank line.

	      The process of applying these completion specifications  when  word  completion  is
	      attempted is described above under Programmable 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 expansion before the complete builtin is invoked.
	      -o comp-option
		      The  comp-option controls several aspects of the compspec's behavior beyond
		      the simple generation of completions.  comp-option may be one of:
		      bashdefault
			      Perform the rest of the default bash completions	if  the  compspec
			      generates no matches.
		      default Use  readline's  default filename completion if the compspec gener-
			      ates no matches.
		      dirnames
			      Perform directory name completion  if  the  compspec  generates  no
			      matches.
		      filenames
			      Tell readline that the compspec generates filenames, so it can per-
			      form any filename-specific  processing  (like  adding  a	slash  to
			      directory  names, quoting special characters, or suppressing trail-
			      ing spaces).  Intended to be used with shell functions.
		      nospace Tell readline not to append a space (the	default)  to  words  com-
			      pleted 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 com-
		      pletions:
		      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 specified as -v.
	      -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 completions are retrieved from the value of
		      the COMPREPLY array variable.
	      -G globpat
		      The pathname expansion pattern globpat is expanded to generate the possible
		      completions.
	      -P prefix
		      prefix  is  added  at  the  beginning of each possible completion after all
		      other options have been applied.
	      -S suffix
		      suffix is appended to each possible completion after all other options have
		      been applied.
	      -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 completed.
	      -X filterpat
		      filterpat  is  a	pattern as used for pathname expansion.  It is applied to
		      the list of possible completions generated 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.

	      The return value is true unless an invalid option is supplied, an option other than
	      -p or -r is supplied without a name argument, an attempt is made to remove  a  com-
	      pletion  specification  for  a  name for which no specification exists, or an error
	      occurs adding a completion specification.

       compopt [-o option] [-DE] [+o option] [name]
	      Modify completion options for each name according to the options, or for	the  cur-
	      rently-executing	completion  if	no  names are supplied.  If no options are given,
	      display the completion options for each name or the current completion.  The possi-
	      ble values of option are those valid for the complete builtin described above.  The
	      -D option indicates that the remaining options should apply to the ``default'' com-
	      mand completion; that is, completion attempted on a command for which no completion
	      has previously been defined.  The -E option indicates that  the  remaining  options
	      should  apply  to  ``empty'' command completion; that is, completion attempted on a
	      blank line.

	      The return value is true unless an invalid option is supplied, an attempt  is  made
	      to  modify  the options for a name for which no completion specification exists, or
	      an output error occurs.

       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 n is not greater than or equal to
	      1.

       declare [-aAfFgilrtux] [-p] [name[=value] ...]
       typeset [-aAfFgilrtux] [-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 with name arguments, additional  options  are  ignored.
	      When -p is supplied without name arguments, it will display the attributes and val-
	      ues of all variables having the attributes specified by the additional options.  If
	      no other options are supplied with -p, declare will display the attributes and val-
	      ues of all shell variables.  The -f option will restrict the display to shell func-
	      tions.   The -F option inhibits the display of function definitions; only the func-
	      tion 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 -g option forces variables to be
	      created  or  modified at the global scope, even when declare is executed in a shell
	      function.  It is ignored in all other cases.  The following options can be used  to
	      restrict	output	to  variables  with  the specified attribute or to give variables
	      attributes:
	      -a     Each name is an indexed array variable (see Arrays above).
	      -A     Each name is an associative array variable (see Arrays above).
	      -f     Use function names only.
	      -i     The variable is treated as an integer; arithmetic evaluation (see ARITHMETIC
		     EVALUATION above) is performed when the variable is assigned a value.
	      -l     When  the	variable  is assigned a value, all upper-case characters are con-
		     verted to lower-case.  The upper-case attribute is disabled.
	      -r     Make names readonly.  These names cannot then be assigned values  by  subse-
		     quent 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.
	      -u     When  the	variable  is assigned a value, all lower-case characters are con-
		     verted to upper-case.  The lower-case attribute is disabled.
	      -x     Mark names for export to subsequent commands via the environment.

	      Using `+' instead of `-' turns off the attribute instead, with the exceptions  that
	      +a may not be used to destroy an array variable and +r will not remove the readonly
	      attribute.  When used in a function, makes each name local, as with the local  com-
	      mand,  unless  the -g option is supplied, 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 assign-
	      ment 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 variable, or  an  attempt  is
	      made to display a non-existent function with -f.

       dirs [+n] [-n] [-clpv]
	      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, 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 directory stack.

       disown [-ar] [-h] [jobspec ...]
	      Without options, each jobspec is removed from the table of active jobs.  If jobspec
	      is not present, and neither -a nor -r is supplied, the shell's notion of	the  cur-
	      rent  job is used.  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 sup-
	      plied, 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 jobspec argument restricts opera-
	      tion 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 following backslash-escaped characters is
	      enabled.	The -E option disables the interpretation  of  these  escape  characters,
	      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 char-
	      acters  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 further output
	      \e
	      \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)
	      \xHH   the  eight-bit character whose value is the hexadecimal value HH (one or two
		     hex digits)
	      \uHHHH the Unicode (ISO/IEC 10646) character whose value is the  hexadecimal  value
		     HHHH (one to four hex digits)
	      \UHHHHHHHH
		     the  Unicode  (ISO/IEC 10646) character whose value is the hexadecimal value
		     HHHHHHHH (one to eight hex digits)

       enable [-a] [-dnps] [-f filename] [name ...]
	      Enable and disable builtin shell commands.  Disabling a builtin allows a disk  com-
	      mand 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 com-
	      mand 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 argu-
	      ments are given, or if the -p option is supplied,  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  sup-
	      plied, 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
	      an error 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 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 beginning of the zeroth argument 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-inter-
	      active 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 exe-
	      cuted.  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  environment  of  subse-
	      quently  executed  commands.   If  the -f option is given, the names refer to func-
	      tions.  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 prop-
	      erty 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 function.

       fc [-e ename] [-lnr] [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  current  command  num-
	      ber).   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 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 editor given by ename is invoked on a file con-
	      taining 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
	      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
	      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  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 control.

       getopts optstring name [args]
	      getopts is used by shell procedures to parse positional parameters.  optstring con-
	      tains  the  option  characters  to  be  recognized; 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 argu-
	      ment, 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.

	      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 displayed, 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]
	      Each  time  hash is invoked, the full pathname of the command name is determined by
	      searching the directories in $PATH and remembered.  Any previously-remembered path-
	      name  is discarded.  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 path-
	      name  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 format 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 [-dms] [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.
	      -d     Display a short description of each pattern
	      -m     Display the description of each pattern in a manpage-like format
	      -s     Display only a short usage synopsis for each pattern

	      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 numbers.  Lines  listed
	      with a * have been modified.  An argument of n lists only the last n lines.  If the
	      shell variable HISTTIMEFORMAT is set and not null, it is used as	a  format  string
	      for  strftime(3)	to  display the time stamp associated with each displayed 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  cur-
		     rent  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,	overwriting  the  history
		     file's 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 variable is set, the time stamp information  associated  with
	      each  history entry is written to the history file, marked with the history comment
	      character.  When the history file is read, lines beginning with the history comment
	      character  followed  immediately	by  a digit are interpreted as timestamps for the
	      previous history line.  The return value is 0 unless an invalid option  is  encoun-
	      tered, 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 following meanings:
	      -l     List process IDs in addition to the normal information.
	      -n     Display  information only about jobs that have changed status since the user
		     was last notified of their status.
	      -p     List only the process ID of the job's process group leader.
	      -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  job-
	      spec.   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  corre-
	      sponding	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  ARITHMETIC  EVALUATION
	      above).  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
	      function and its children.  With no operands, local writes a list  of  local  vari-
	      ables  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,  an  invalid
	      name is supplied, or name is a readonly variable.

       logout Exit a login shell.

       mapfile [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]
       readarray  [-n  count]  [-O  origin]  [-s  count]  [-t] [-u fd] [-C callback] [-c quantum]
       [array]
	      Read lines from the standard input into the indexed array variable array,  or  from
	      file  descriptor	fd  if	the  -u  option is supplied.  The variable MAPFILE is the
	      default array.  Options, if supplied, have the following meanings:
	      -n     Copy at most count lines.	If count is 0, all lines are copied.
	      -O     Begin assigning to array at index origin.	The default index is 0.
	      -s     Discard the first count lines read.
	      -t     Remove a trailing newline from each line read.
	      -u     Read lines from file descriptor fd instead of the standard input.
	      -C     Evaluate callback each time quantum lines are read.  The -c option specifies
		     quantum.
	      -c     Specify the number of lines read between each call to callback.

	      If -C is specified without -c, the default quantum is 5000.  When callback is eval-
	      uated, it is supplied the index of the next array element to be  assigned  and  the
	      line to be assigned to that element as additional arguments.  callback is evaluated
	      after the line is read but before the array element is assigned.

	      If not supplied with an explicit origin, mapfile will clear array before	assigning
	      to it.

	      mapfile  returns	successfully  unless an invalid option or option argument is sup-
	      plied, array is invalid or unassignable, or if array is not an indexed array.

       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 following meanings:
	      -n     Suppresses the normal change of directory when removing directories from the
		     stack, so that only the stack is manipulated.
	      +n     Removes  the  nth	entry  counting  from the left of the list shown by 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.

	      If the popd command is successful, a dirs is performed as well, and the return sta-
	      tus is 0.  popd returns false if an invalid option is  encountered,  the	directory
	      stack is empty, a non-existent 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  for-
	      mat.   The  -v  option  causes the output to be assigned to the variable var rather
	      than being printed to the standard output.

	      The format is a character string which contains three types of objects: plain char-
	      acters,  which  are  simply  copied to standard output, character escape sequences,
	      which are converted and copied to the standard output, and  format  specifications,
	      each  of which causes printing of the next successive argument.  In addition to the
	      standard printf(1) format specifications, printf interprets  the	following  exten-
	      sions:
	      %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).
	      %q     causes printf to output the corresponding argument in a format that  can  be
		     reused as shell input.
	      %(datefmt)T
		     causes printf to output the date-time string resulting from using datefmt as
		     a format string for strftime(3).  The corresponding argument is  an  integer
		     representing  the	number	of seconds since the epoch.  Two special argument
		     values may be used: -1 represents the current time, and  -2  represents  the
		     time the shell was invoked.

	      Arguments to non-string format specifiers are treated as C constants, except that a
	      leading plus or minus sign is allowed, and if the leading character is a single  or
	      double quote, the value is the ASCII value of the following character.

	      The  format  is reused as necessary to consume all of the arguments.  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] [+n] [-n]
       pushd [-n] [dir]
	      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     Suppresses  the  normal  change  of directory when adding directories to the
		     stack, so that only the stack is manipulated.
	      +n     Rotates the stack so that the nth directory (counting from the left  of  the
		     list shown by 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.
	      dir    Adds dir to the directory stack at the top, making it the new current  work-
		     ing 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 directory stack is empty, a non-existent directory stack ele-
	      ment 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] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t time-
       out] [-u fd] [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 inter-
	      vening  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 following 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.  Readline uses the current (or default,
		     if line editing was not previously active) editing settings.
	      -i text
		     If readline is being used to read the line, text is placed into the  editing
		     buffer before editing begins.
	      -n nchars
		     read  returns after reading nchars characters rather than waiting for a com-
		     plete line of input, but honor a delimiter if fewer than  nchars  characters
		     are read before the delimiter.
	      -N nchars
		     read returns after reading exactly nchars characters rather than waiting for
		     a complete line of input, unless EOF  is  encountered  or	read  times  out.
		     Delimiter	characters encountered in the input are not treated specially and
		     do not cause read to return until nchars characters are read.
	      -p prompt
		     Display prompt  on  standard  error,  without  a  trailing  newline,  before
		     attempting to read any input.  The prompt is displayed only if input is com-
		     ing from a terminal.
	      -r     Backslash does not act as an escape character.  The backslash is  considered
		     to  be part of the line.  In particular, a backslash-newline pair may not be
		     used as a line continuation.
	      -s     Silent mode.  If input is coming from a terminal, characters 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.  timeout may be a decimal number with a frac-
		     tional portion following the decimal point.  This option is  only	effective
		     if  read  is  reading input from a terminal, pipe, or other special file; it
		     has no effect when reading from  regular  files.	If  timeout  is  0,  read
		     returns  success  if  input  is  available on the specified file descriptor,
		     failure otherwise.  The exit status is greater than 128 if  the  timeout  is
		     exceeded.
	      -u fd  Read input from file descriptor fd.

	      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, read times  out  (in  which
	      case  the  return  code is greater than 128), or an invalid file descriptor is sup-
	      plied as the argument to -u.

       readonly [-aAf] [-p] [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 correspond-
	      ing to the names are so marked.  The -a option restricts the variables  to  indexed
	      arrays;  the  -A	option	restricts  the	variables to associative arrays.  If both
	      options are supplied, -A takes precedence.  If no name arguments are given,  or  if
	      the  -p  option  is  supplied,  a list of all readonly names is printed.	The other
	      options may be used to restrict the output to a  subset  of  the	set  of  readonly
	      names.   The -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  variable  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 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  function  body.   If
	      used  outside  a function, but during execution of a script by the .  (source) com-
	      mand, 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 exe-
	      cuted before execution resumes after the function or script.

       set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]
       set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg ...]
	      Without options, the name and value of each shell variable are displayed in a  for-
	      mat  that  can  be reused as input for setting or resetting the currently-set vari-
	      ables.  Read-only variables cannot 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
	      option  processing  are  treated	as  values  for the positional parameters and are
	      assigned, in order, to $1, $2, ...  $n.  Options, if specified, have the	following
	      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  immediately,  rather  than
		      before the next primary prompt.  This is effective only when job control is
		      enabled.
	      -e      Exit immediately if a pipeline (which may consist of a single  simple  com-
		      mand),   a subshell command enclosed in parentheses, or one of the commands
		      executed as part of a command list enclosed by braces  (see  SHELL  GRAMMAR
		      above)  exits  with a non-zero status.  The shell does not exit if the com-
		      mand that fails is part of the command list immediately following  a  while
		      or until keyword, part of the test following the if or elif reserved words,
		      part of any command executed in a && or || list except the command  follow-
		      ing  the	final && or ||, any command in a pipeline but the last, or if the
		      command's return value is being inverted with !.	A trap on ERR, if set, is
		      executed before the shell exits.	This option applies to the shell environ-
		      ment and each subshell environment separately (see COMMAND EXECUTION  ENVI-
		      RONMENT  above),	and  may cause subshells to exit before executing all the
		      commands in the subshell.
	      -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 envi-
		      ronment 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 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 following:
		      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  interactive, unless the shell is
			      started with the --noediting option.  This also affects the editing
			      interface used for read -e.
		      errexit Same as -e.
		      errtrace
			      Same as -E.
		      functrace
			      Same as -T.
		      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  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 dis-
			      abled by default.
		      posix   Change the behavior of bash where  the  default  operation  differs
			      from the POSIX standard to match the standard (posix mode).
		      privileged
			      Same as -p.
		      verbose Same as -v.
		      vi      Use  a  vi-style command line editing interface.	This also affects
			      the editing interface used for read -e.
		      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 com-
		      mands 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,  BASHOPTS, CDPATH, and GLOBIGNORE variables, if they appear
		      in the environment, are ignored.	If the shell is started with  the  effec-
		      tive  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  effec-
		      tive 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 and parameters other than the special parameters "@"
		      and "*" as an error when performing parameter expansion.	If  expansion  is
		      attempted on an unset variable or parameter, the shell prints an error mes-
		      sage, 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 com-
		      mand,  or  arithmetic  for command, display the expanded value of PS4, fol-
		      lowed 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 <> re-
		      direction operators.  This may be overridden when creating output files  by
		      using the redirection operator >| instead of >.
	      -E      If  set, any trap on ERR is inherited by shell functions, command substitu-
		      tions, and commands executed in a subshell environment.  The  ERR  trap  is
		      normally not inherited 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 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
		      positional 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 specified as  argu-
	      ments  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 $1	....   Parameters  repre-
	      sented 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 behavior.  With no
	      options, or with the -p option, a list of all settable 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	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 arguments are  given  with
		     -q,  the  return status 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 display is limited to
	      those options which are set or unset, respectively.  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:

	      autocd  If set, a command name that is the name of a directory is executed as if it
		      were the argument to the cd command.  This option is only used by  interac-
		      tive shells.
	      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 component in a cd com-
		      mand will be corrected.  The errors checked for are transposed  characters,
		      a missing character, and one character too many.	If a correction 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 execute it.  If a hashed command no longer exists, a normal  path
		      search is performed.
	      checkjobs
		      If  set, bash lists the status of any stopped and running jobs before exit-
		      ing an interactive shell.  If any jobs are running, this causes the exit to
		      be deferred until a second exit is attempted without an intervening command
		      (see JOB CONTROL above).	The shell always postpones exiting  if	any  jobs
		      are stopped.
	      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.
	      compat31
		      If  set,	bash  changes its behavior to that of version 3.1 with respect to
		      quoted arguments to the [[ conditional command's =~ operator.
	      compat32
		      If set, bash changes its behavior to that of version 3.2	with  respect  to
		      locale-specific string comparison when using the [[ conditional command's <
		      and > operators.	Bash versions prior to bash-4.1 use ASCII  collation  and
		      strcmp(3);  bash-4.1  and later use the current locale's collation sequence
		      and strcoll(3).
	      compat40
		      If set, bash changes its behavior to that of version 4.0	with  respect  to
		      locale-specific string comparison when using the [[ conditional command's <
		      and > operators (see previous item) and the effect of interrupting  a  com-
		      mand list.
	      compat41
		      If  set, bash, when in posix mode, treats a single quote in a double-quoted
		      parameter expansion as a special character.  The single quotes  must  match
		      (an  even  number) and the characters between the single quotes are consid-
		      ered quoted.  This is the behavior of posix mode through version 4.1.   The
		      default bash behavior remains as in previous versions.
	      direxpand
		      If  set,	bash  replaces directory names with the results of word expansion
		      when performing filename completion.  This  changes  the	contents  of  the
		      readline	editing  buffer.   If not set, bash attempts to preserve what the
		      user typed.
	      dirspell
		      If set, bash attempts spelling correction on directory  names  during  word
		      completion if the directory name initially supplied does not exist.
	      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
		      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 interactive 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  subroutine (a shell function or a shell
			     script executed by the . or source builtins), a call  to  return  is
			     simulated.
		      4.     BASH_ARGC	and  BASH_ARGV are updated as described in their descrip-
			     tions above.
		      5.     Function tracing is enabled:  command substitution, 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 ERR trap.
	      extglob If  set, the extended pattern matching features described above under Path-
		      name 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 possible completions.  See SHELL VARIABLES above for a description
		      of FIGNORE.  This option is enabled by default.
	      globstar
		      If  set, the pattern ** used in a pathname expansion context will match all
		      files and zero or more directories and subdirectories.  If the  pattern  is
		      followed by a /, only directories and subdirectories match.
	      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 history substitution are
		      not immediately passed to the shell parser.  Instead, the resulting line is
		      loaded into the readline editing buffer, allowing further modification.
	      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 interactive  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.
	      lastpipe
		      If set, and job control is not active, the shell runs the last command of a
		      pipeline not executed in the background in the current shell environment.
	      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  INVOCA-
		      TION 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 displayed.
	      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 perform-
		      ing 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 Programmable Completion
		      above) are enabled.  This option is enabled by default.
	      promptvars
		      If  set,	prompt strings undergo parameter expansion, command 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 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
		      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.  A login
	      shell cannot be suspended; the -f option can be used to override this and force the
	      suspension.  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 com-
	      posed of the primaries described above under CONDITIONAL	EXPRESSIONS.   test  does
	      not accept any options, nor does it accept and ignore an argument of -- as signify-
	      ing the end of options.

	      Expressions may be combined using the following  operators,  listed  in  decreasing
	      order of precedence.  The evaluation depends on the number of arguments; see below.
	      Operator precedence is used when there are five or more arguments.
	      ! expr True if expr is false.
	      ( expr )
		     Returns the value of expr.  This may be used to override the  normal  prece-
		     dence 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 num-
	      ber 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 argument 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 con-
		     ditional operator, the expression is false.
	      3 arguments
		     The following conditions are applied in the order	listed.   If  the  second
		     argument  is one of the binary conditional operators listed above under CON-
		     DITIONAL EXPRESSIONS, the result of the expression  is  the  result  of  the
		     binary  test using the first and third arguments as operands.  The -a and -o
		     operators are considered binary operators when there  are	three  arguments.
		     If  the  first  argument is !, the value is the negation of the two-argument
		     test using the second and third arguments.  If the first argument is exactly
		     (	and  the third argument is exactly ), the result is the one-argument test
		     of the second argument.  Otherwise, the expression is false.
	      4 arguments
		     If the first argument is !, the result is the negation of the three-argument
		     expression  composed  of the remaining arguments.	Otherwise, the expression
		     is parsed and 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.

	      When used with test or [, the < and > operators sort lexicographically using  ASCII
	      ordering.

       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 corresponding numbers.  Each sigspec is either a signal name
	      defined  in  <signal.h>, 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 com-
	      mand, 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 RETURN, the command arg is executed each time a
	      shell function or a script executed with the . or source builtins finishes  execut-
	      ing.

	      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 command exe-
	      cuted in a && or || list, or if the command's return value is being inverted via !.
	      These are the same conditions obeyed by the errexit option.

	      Signals ignored upon entry to  the  shell  cannot  be  trapped,  reset  or  listed.
	      Trapped  signals that are not being ignored are reset to their original values in a
	      subshell or subshell environment when one is created.  The return status	is  false
	      if any 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,  key-
	      word,  function,	builtin,  or file if name is an alias, shell reserved word, func-
	      tion, 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.
	      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
	      function lookup, as with the command builtin.  type returns  true  if  all  of  the
	      arguments are found, false if any are not found.

       ulimit [-HSTabcdefilmnpqrstuvx [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
	      by a non-root user once it is set; a soft limit may be increased up to the value of
	      the  hard  limit.  If neither -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  omit-
	      ted,  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 follows:
	      -a     All current limits are reported
	      -b     The maximum socket buffer size
	      -c     The maximum size of core files created
	      -d     The maximum size of a process's data segment
	      -e     The maximum scheduling priority ("nice")
	      -f     The maximum size of files written by the shell and its children
	      -i     The maximum number of pending signals
	      -l     The maximum size that may be locked into memory
	      -m     The maximum resident set size (many systems do not honor this limit)
	      -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 real-time scheduling 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  and,  on  some
		     systems, to its children
	      -x     The maximum number of file locks
	      -T     The maximum number of threads

	      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 -T, -b, -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 symbolic form; the
	      default output is an octal number.  If the -p option is supplied, and mode is omit-
	      ted,  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
	      function, and the function definition is removed.  Each unset variable or  function
	      is  removed  from  the  environment  passed  to  subsequent  commands.   If  any of
	      COMP_WORDBREAKS, RANDOM, SECONDS, LINENO, HISTCMD, FUNCNAME,  GROUPS,  or  DIRSTACK
	      are unset, they lose their special properties, even if they are subsequently reset.
	      The exit status is true unless a name is readonly.

       wait [n ...]
	      Wait for each specified process and return its termination status.  Each n may be a
	      process  ID  or  a job specification; if a job spec is given, all processes in that
	      job's pipeline are waited for.  If n is not given, all currently active child  pro-
	      cesses  are  waited for, and the return status is zero.  If n specifies a non-exis-
	      tent 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-4.0				   2004 Apr 20				 BASH_BUILTINS(1)
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