builtins

BASH-BUILTINS(7)       Miscellaneous Information Manual       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.   The  :, true, false, and test builtins do not accept options
       and do not treat -- specially.  The exit, logout, return,  break,  con-
       tinue,  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  interpreta-
       tion.
       : [arguments]
              No  effect;  the command does nothing beyond expanding arguments
              and performing any specified redirections.  The return status is
              zero.

        .  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,
              filenames in PATH are used  to  find  the  directory  containing
              filename.  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.   If  the  -T  option is
              enabled, source inherits any trap on DEBUG; if it  is  not,  any
              DEBUG  trap  string  is  saved  and  restored around the call to
              source, and source unsets the DEBUG trap while it executes.   If
              -T  is not set, and the sourced file changes the DEBUG trap, the
              new value is retained when source completes.  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 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] [-lpsvPSVX]
       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 [-m keymap] keyseq: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  (vi-move
                     is  also  a  synonym); emacs is equivalent to emacs-stan-
                     dard.
              -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 read-
                     line 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  READ-
                     LINE_POINT,  those  new  values  will be reflected in the
                     editing state.
              -X     List all key sequences bound to shell  commands  and  the
                     associated  commands  in  a  format that can be reused as
                     input.

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

       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 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.

       caller [expr]
              Returns the context of any active subroutine call (a shell func-
              tion or a script executed with the . or source builtins).  With-
              out expr, caller displays the line number and source filename of
              the  current subroutine call.  If a non-negative integer is sup-
              plied 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 current frame is frame 0.
              The return value is 0 unless the shell is not executing  a  sub-
              routine  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.  if dir  is  not  supplied,
              the  value of the HOME shell variable is the default.  Any addi-
              tional arguments following dir are ignored.  The variable CDPATH
              defines  the  search path for the directory containing dir: each
              directory name in  CDPATH  is  searched  for  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 causes cd to  use  the  physical  directory
              structure  by  resolving symbolic links while traversing dir and
              before processing instances of .. in dir (see also the -P option
              to the set builtin command); the -L option forces symbolic links
              to be followed by resolving the link after processing  instances
              of .. in dir.  If .. appears in dir, it is processed by removing
              the immediately previous pathname component from dir, back to  a
              slash  or  the  beginning  of dir.  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 unsuccessful status.  On systems that support it,  the
              -@  option  presents  the  extended attributes associated with a
              file as a directory.  An argument of - is converted  to  $OLDPWD
              before the directory change is attempted.  If a non-empty direc-
              tory 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 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  filename
              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 program-
              mable completion code had generated them directly from a comple-
              tion  specification  with the same flags.  If word is specified,
              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] [-DE] [-A action] [-G glob-
       pat] [-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 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  -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  Program-
              mable 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-
                      spec's  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  readline's  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, quoting special characters, or  suppress-
                              ing  trailing spaces).  Intended to be used with
                              shell functions.
                      noquote Tell readline not to quote the  completed  words
                              if  they are filenames (quoting filenames is the
                              default).
                      nosort  Tell readline not to sort the list  of  possible
                              completions alphabetically.
                      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.
              -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 the function is executed, the
                      first argument ($1) is the name  of  the  command  whose
                      arguments  are being completed, the second argument ($2)
                      is the word being completed, and the third argument ($3)
                      is  the  word  preceding the word being completed on the
                      current command line.  When it  finishes,  the  possible
                      completions  are retrieved from the value of the COMPRE-
                      PLY 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 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.
              -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.
              -X filterpat
                      filterpat  is  a pattern as used for pathname expansion.
                      It is applied to the list of possible completions gener-
                      ated  by  the  preceding options and arguments, and each
                      completion matching 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 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.

       compopt [-o option] [-DE] [+o option] [name]
              Modify  completion  options  for  each  name  according  to  the
              options,  or  for the currently-executing completion if no names
              are supplied.  If no options are given, display  the  completion
              options  for  each name or the current completion.  The possible
              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'' 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 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 [-aAfFgilnrtux] [-p] [name[=value] ...]
       typeset [-aAfFgilnrtux] [-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, other than -f  and  -F,
              are  ignored.   When  -p  is supplied without name arguments, it
              will display the attributes and values of all  variables  having
              the attributes specified by the additional options.  If no other
              options  are  supplied  with  -p,  declare  will   display   the
              attributes  and  values  of  all shell variables.  The -f option
              will restrict the display to shell  functions.   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 each name 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 follow-
              ing 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 evalua-
                     tion (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 converted to lower-case.   The  upper-case
                     attribute is disabled.
              -n     Give  each  name  the nameref attribute, making it a name
                     reference to another variable.  That  other  variable  is
                     defined  by  the  value of name.  All references, assign-
                     ments, and attribute modifications to name, except  those
                     using  or changing the -n attribute itself, are performed
                     on the variable referenced by name's value.  The  nameref
                     attribute cannot be applied to array variables.
              -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.
              -u     When  the  variable  is  assigned a value, all lower-case
                     characters are converted 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 vari-
              able and +r will not remove the readonly attribute.   When  used
              in a function, declare and typeset make each name local, as with
              the local command, unless the -g option is supplied.  If a vari-
              able  name  is  followed by =value, the value of the variable is
              set to value.  When using -a or -A and the  compound  assignment
              syntax  to  create array variables, additional attributes do not
              take effect until subsequent assignments.  The return value is 0
              unless  an  invalid option is encountered, an attempt is made to
              define a function using ``-f foo=bar'', an attempt  is  made  to
              assign  a  value  to  a readonly variable, an attempt is made to
              assign a value to an array variable without using  the  compound
              assignment  syntax (see 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.   The  current directory is always the
              first directory in the stack.
              -c     Clears  the  directory  stack  by  deleting  all  of  the
                     entries.
              -l     Produces  a  listing  using  full  pathnames; 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.
              +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.

              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 ... | pid ... ]
              Without options, remove each jobspec from the  table  of  active
              jobs.   If jobspec is not present, and neither the -a nor the -r
              option is supplied, the current 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 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 0 unless a write error occurs.  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  interpreta-
              tion  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 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 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 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 sup-
              plied, the list printed includes all builtins, with  an  indica-
              tion  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 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 can-
              not be executed for some reason, a non-interactive shell  exits,
              unless  the  execfail shell option is enabled.  In that case, it
              returns failure.  An interactive shell returns  failure  if  the
              file cannot be executed.  If command is not specified, any redi-
              rections 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 names  of  all  exported
              variables  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 sup-
              plied with a name that is not a function.

       fc [-e ename] [-lnr] [first] [last]
       fc -s [pat=rep] [cmd]
              The first form selects a range of commands from  first  to  last
              from  the  history  list  and  displays or edits and re-executes
              them.  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 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 other-
              wise.  If first is not specified it is set to the previous  com-
              mand 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, vi is used.  When editing is com-
              plete, the edited commands are echoed and executed.

              In the second form, command is re-executed after  each  instance
              of  pat  is  replaced by rep.  Command is intepreted the same as
              first above.  A useful alias to use with this is ``r="fc  -s"'',
              so  that  typing  ``r  cc'' runs the last command beginning with
              ``cc'' and typing ``r'' re-executes the last command.

              If the first form is used, the  return  value  is  0  unless  an
              invalid  option  is encountered or 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 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 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]
              Each time hash is invoked, the full pathname of the command name
              is  determined  by searching the directories in $PATH and remem-
              bered.  Any previously-remembered pathname is discarded.  If the
              -p option is supplied, no path search is performed, and filename
              is used as the full filename 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  argu-
              ments  are  supplied  with  -t,  the  name is printed before the
              hashed full pathname.  The -l option causes output  to  be  dis-
              played in a format that may be reused as input.  If no arguments
              are given, or if only -l is supplied, information  about  remem-
              bered  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 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 to the history file.
                     These are history lines entered since  the  beginning  of
                     the current bash session, but not already appended 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 append them to
                     the current history list.
              -w     Write the current history list to the history file, over-
                     writing 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  informa-
              tion  associated  with each history entry is written to the his-
              tory file, marked with the history comment character.  When  the
              history  file  is read, lines beginning with the history comment
              character followed immediately by a  digit  are  interpreted  as
              timestamps for the following history entry.  The return value is
              0 unless an invalid option is encountered, an error occurs while
              reading  or  writing the history file, an invalid offset is sup-
              plied 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.
              -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     Display only running jobs.
              -s     Display only 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|-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.  The -L option is
              equivalent to -l.  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  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 func-
              tion and its children.  If name is -, the set of  shell  options
              is  made  local to the function in which local is invoked: shell
              options changed using the set builtin inside  the  function  are
              restored  to  their  original  values when the function returns.
              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.

       mapfile [-d delim] [-n count] [-O origin] [-s count] [-t] [-u  fd]  [-C
       callback] [-c quantum] [array]
       readarray [-d delim] [-n count] [-O origin] [-s count] [-t] [-u fd] [-C
       callback] [-c quantum] [array]
              Read lines from the standard input into the indexed array  vari-
              able  array, or from file descriptor fd if the -u option is sup-
              plied.  The variable MAPFILE is the default array.  Options,  if
              supplied, have the following meanings:
              -d     The  first  character  of delim is used to terminate each
                     input line, rather than newline.
              -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 delim (default newline) from each  line
                     read.
              -u     Read  lines  from file descriptor fd instead of the stan-
                     dard 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 evaluated, it is supplied the index of the next
              array element to be assigned and the line to be assigned to that
              element  as  additional  arguments.  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 supplied, 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 follow-
              ing 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 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 -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  characters, which are simply copied to standard
              output, character escape  sequences,  which  are  converted  and
              copied  to  the standard output, and format specifications, each
              of which causes printing of the next  successive  argument.   In
              addition to the standard printf(1) format specifications, printf
              interprets the following extensions:
              %b     causes printf to expand backslash escape sequences in the
                     corresponding argument in the same way as echo -e.
              %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.  If no
                     argument is specified, conversion behaves as  if  -1  had
                     been  given.   This  is  an exception to the usual printf
                     behavior.

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

              The  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] [+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,  pushd  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 rotating
                     or adding directories to the  stack,  so  that  only  the
                     stack is manipulated.
              +n     Rotates  the  stack  so  that the nth directory (counting
                     from the left of the list shown by  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 working directory as if it had been  supplied
                     as the argument to the cd builtin.

              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] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p
       prompt] [-t timeout] [-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,  split
              into  words  as  described  above  under Word Splitting, and the
              first word is assigned to the first name, the second word to the
              second name, and so on.  If there are more words than names, the
              remaining words and their intervening delimiters are assigned to
              the  last  name.   If  there are fewer words read from the input
              stream than names, the remaining names are assigned  empty  val-
              ues.   The  characters  in  IFS  are used to split the line into
              words  using  the  same  rules  the  shell  uses  for  expansion
              (described above under Word Splitting).  The backslash character
              (\) may be used to remove any special meaning for the next char-
              acter  read  and  for  line continuation.  Options, if supplied,
              have the following meanings:
              -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.  Read-
                     line 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 complete line of input, but honors a delim-
                     iter 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 charac-
                     ters encountered in the input are not  treated  specially
                     and  do  not cause read to return until nchars characters
                     are read.  The result is not split on the  characters  in
                     IFS;  the intent is that the variable is assigned exactly
                     the characters read (with the exception of backslash; see
                     the -r option below).
              -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 (or a specified number  of  characters)  is
                     not  read within timeout seconds.  timeout may be a deci-
                     mal number with a fractional portion following the  deci-
                     mal  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 read times out, read saves any partial input read into
                     the  specified  variable  name.   If  timeout  is 0, read
                     returns immediately, without trying  to  read  any  data.
                     The  exit status is 0 if input is available on the speci-
                     fied file descriptor, non-zero otherwise.  The exit  sta-
                     tus is greater than 128 if the timeout is exceeded.
              -u fd  Read input from file descriptor fd.

              If no names are supplied, the line read is assigned to the vari-
              able REPLY.  The exit status  is  zero,  unless  end-of-file  is
              encountered, read times out (in which case the status is greater
              than 128), a variable assignment error (such as assigning  to  a
              readonly variable) occurs, or an invalid file descriptor is sup-
              plied as the argument to -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 corresponding 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 stop executing and return the value  speci-
              fied  by n to its caller.  If n is omitted, the return status is
              that of the last command executed  in  the  function  body.   If
              return  is  executed by a trap handler, the last command used to
              determine the status is the last  command  executed  before  the
              trap  handler.   if  return is executed during a DEBUG trap, the
              last command used to determine the status is  the  last  command
              executed  by  the  trap  handler  before return was invoked.  If
              return is 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 n is supplied, the return value is its  least
              significant  8 bits.  The return status is non-zero if return is
              supplied a non-numeric argument, or is used outside  a  function
              and  not  during execution of a script by . or source.  Any com-
              mand associated with the RETURN trap is executed  before  execu-
              tion 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 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 option processing are treated as val-
              ues for the positional parameters and are assigned, in order, to
              $1,  $2,  ...   $n.   Options,  if specified, have the following
              meanings:
              -a      Each variable or function that is created or modified is
                      given  the export attribute and marked 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 pipeline (which may consist  of  a
                      single  simple  command),  a list, or a compound 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 following the if or
                      elif reserved words, part of any command executed  in  a
                      &&  or || list except the command following the final &&
                      or ||, any command in a pipeline but the last, or if the
                      command's  return  value is being inverted with !.  If a
                      compound command other than a subshell  returns  a  non-
                      zero  status because a command failed while -e was being
                      ignored, the shell does not exit.  A  trap  on  ERR,  if
                      set,  is  executed  before the shell exits.  This option
                      applies to the shell environment and each subshell envi-
                      ronment  separately  (see  COMMAND EXECUTION ENVIRONMENT
                      above), and may cause subshells to exit before executing
                      all the commands in the subshell.

                      If  a  compound  command or shell function executes in a
                      context where -e is being ignored, none of the  commands
                      executed  within  the  compound command or function body
                      will be affected by the -e setting, even if  -e  is  set
                      and  a  command returns a failure status.  If a compound
                      command or shell function sets -e while executing  in  a
                      context  where -e is ignored, that setting will not have
                      any effect until the compound  command  or  the  command
                      containing the function call completes.
              -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).  All  processes  run
                      in a separate process group.  When a background job com-
                      pletes, the shell prints a line containing its exit sta-
                      tus.
              -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.  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 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  standard  to
                              match  the  standard (posix mode).  See SEE ALSO
                              below for a reference to a document that details
                              how posix mode affects bash's behavior.
                      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 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,
                      BASHOPTS, CDPATH,  and  GLOBIGNORE  variables,  if  they
                      appear in the environment, are ignored.  If the shell is
                      started with the effective user (group) id not equal  to
                      the  real user (group) id, and the -p option is not sup-
                      plied, these actions are taken and the effective user id
                      is  set  to  the real user id.  If the -p option is sup-
                      plied at startup, the effective user id  is  not  reset.
                      Turning  this  option  off causes the effective user and
                      group ids to be set to the real user and group ids.
              -t      Exit after reading and executing one command.
              -u      Treat unset variables and parameters other than the spe-
                      cial  parameters "@" and "*" as an error when performing
                      parameter expansion.  If expansion is  attempted  on  an
                      unset  variable  or parameter, the shell prints an error
                      message, and, if not interactive, exits with a  non-zero
                      status.
              -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 resolve 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 settings controlling optional shell behav-
              ior.  The settings can be either those listed below, or, if  the
              -o option is used, those available with the -o option to the set
              builtin command.  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 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, shopt
              shows only 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  com-
                      mand.  This option is only used by interactive 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 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 filename 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.
              checkjobs
                      If set, bash lists the status of any stopped and running
                      jobs  before  exiting an interactive shell.  If any jobs
                      are running, this causes the exit to be deferred until a
                      second  exit is attempted without an intervening command
                      (see 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  COL-
                      UMNS.
              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 and locale-specific string compar-
                      ison when using the [[ conditional  command's  <  and  >
                      operators.   Bash  versions  prior to bash-4.1 use ASCII
                      collation and strcmp(3); bash-4.1 and later use the cur-
                      rent locale's collation sequence and strcoll(3).
              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
                      (see previous item) and the  effect  of  interrupting  a
                      command  list.   Bash  versions 3.2 and earlier continue
                      with the next command in the list after  one  terminates
                      due to an interrupt.
              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 description of compat31) and the effect  of  inter-
                      rupting  a  command  list.   Bash versions 4.0 and later
                      interrupt the list as if the shell received  the  inter-
                      rupt;  previous  versions continue with the next command
                      in the list.
              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  num-
                      ber)  and  the  characters between the single quotes are
                      considered quoted.  This is the behavior of  posix  mode
                      through  version 4.1.  The default bash behavior remains
                      as in previous versions.
              compat42
                      If set, bash does not process the replacement string  in
                      the  pattern  substitution  word  expansion  using quote
                      removal.
              compat43
                      If set, bash does not print  a  warning  message  if  an
                      attempt  is  made to use a quoted compound array assign-
                      ment as an argument to  declare,  makes  word  expansion
                      errors  non-fatal  errors that cause the current command
                      to fail (the default behavior  is  to  make  them  fatal
                      errors that cause the shell to exit), and does not reset
                      the loop state when a shell function is  executed  (this
                      allows  break  or continue in a shell function to affect
                      loops in the caller's context).
              complete_fullquote
                      If set, bash quotes all shell  metacharacters  in  file-
                      names  and  directory  names when performing completion.
                      If not set, bash removes metacharacters such as the dol-
                      lar  sign from the set of characters that will be quoted
                      in completed filenames when these metacharacters  appear
                      in  shell  variable references in words to be completed.
                      This means that dollar  signs  in  variable  names  that
                      expand  to  directories will not be quoted; however, any
                      dollar signs appearing in filenames will not be  quoted,
                      either.   This  is  active only when bash is using back-
                      slashes to quote completed filenames.  This variable  is
                      set  by  default,  which is the default bash behavior in
                      versions through 4.2.
              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  buf-
                      fer.   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 ini-
                      tially 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 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 at  shell  invocation,  arrange  to  execute  the
                      debugger  profile  before the shell starts, identical to
                      the --debugger option.  If set after invocation,  behav-
                      ior 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),  the  shell
                             simulates a call to return.
                      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 ERR 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.
              globasciiranges
                      If  set,  range  expressions  used  in  pattern matching
                      bracket expressions (see Pattern Matching above)  behave
                      as  if  in the traditional C locale when performing com-
                      parisons.   That  is,  the  current  locale's  collating
                      sequence  is  not taken into account, so b will not col-
                      late between A and  B,  and  upper-case  and  lower-case
                      ASCII characters will collate together.
              globstar
                      If set, the pattern ** used in a pathname expansion con-
                      text will match all files and zero or  more  directories
                      and  subdirectories.  If the pattern is followed by a /,
                      only directories and subdirectories match.
              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.
              inherit_errexit
                      If set, command substitution inherits the value  of  the
                      errexit  option, instead of unsetting it in the subshell
                      environment.  This option is enabled when posix mode  is
                      enabled.
              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 back-
                      ground 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  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, when performing pattern substi-
                      tution word expansions, or when filtering possible  com-
                      pletions as part of programmable completion.
              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.  A login shell cannot be suspended; the -f option can be
              used to override this and force the suspension.  The return sta-
              tus is 0 unless the shell is a login shell and -f  is  not  sup-
              plied, or if job control is not enabled.

       test expr
       [ expr ]
              Return a status of 0 (true) or 1 (false) depending on the evalu-
              ation of the conditional expression expr.  Each operator and op-
              erand  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.   The  evaluation
              depends on the number of arguments; see below.  Operator  prece-
              dence 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 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
                     The following conditions are applied in the order listed.
                     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.  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.   Other-
                     wise, the expression is false.
              4 arguments
                     If the first argument is !, the result is the negation of
                     the three-argument expression composed of  the  remaining
                     arguments.  Otherwise, the expression is parsed and eval-
                     uated according to  precedence  using  the  rules  listed
                     above.
              5 or more arguments
                     The  expression  is  parsed  and  evaluated  according to
                     precedence using the rules listed above.

              When used with test or [, the < and  >  operators  sort  lexico-
              graphically 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  cor-
              responding  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  exe-
              cuted  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 RETURN, the command arg is executed each time a shell
              function or a script executed with the . or source builtins fin-
              ishes executing.

              If a sigspec is ERR, the command  arg  is  executed  whenever  a
              pipeline (which may consist of a single simple command), a list,
              or a compound command returns a non-zero exit status, subject to
              the  following  conditions.  The 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 executed in a && or || list except the command
              following  the final && or ||, any command in a pipeline but the
              last, or if the command's return value is being  inverted  using
              !.   These  are  the  same conditions obeyed by the errexit (-e)
              option.

              Signals ignored upon entry to the shell  cannot  be  trapped  or
              reset.   Trapped signals that are not being ignored are reset to
              their original values in a subshell or subshell environment when
              one  is  created.   The return status is false if any 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, which is not necessar-
              ily 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 [-HSabcdefiklmnpqrstuvxPT [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 speci-
              fied, 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 inter-
              preted 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
              -k     The maximum number of kqueues that may be allocated
              -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
              -P     The maximum number of pseudoterminals
              -T     The maximum number of threads

              If  limit  is given, and the -a option is not used, limit is the
              new value of the specified resource.  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;  -P,  -T, -b, -k, -n, and -u, which are unscaled values;
              and, when in Posix mode, -c and -f, which are in 512-byte incre-
              ments.  The return status is 0 unless an invalid option or argu-
              ment is supplied, or an error occurs while setting a new limit.

       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] [-n] [name ...]
              For  each  name,  remove the corresponding variable or function.
              If the -v option is given, each name refers to a shell variable,
              and  that  variable  is removed.  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.  If the -n option
              is supplied, and name is a variable with the nameref  attribute,
              name  will  be unset rather than the variable it references.  -n
              has no effect if the -f option is supplied.  If no  options  are
              supplied,  each  name refers to a variable; if there is no vari-
              able by that name, any function with that name is  unset.   Each
              unset  variable  or  function  is  removed  from the environment
              passed to subsequent commands.  If any of COMP_WORDBREAKS,  RAN-
              DOM, SECONDS, LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are
              unset, they lose their special properties, even if they are sub-
              sequently reset.  The exit status is true unless a name is read-
              only.

       wait [-n] [n ...]
              Wait for each specified child 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 the -n
              option  is  supplied,  wait  waits  for any job to terminate and
              returns its exit status.  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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