path: root/doc/builtins.0

BASH_BUILTINS(1)            General Commands Manual           BASH_BUILTINS(1)



NNAAMMEE
       bash,  :,  .,  [, alias, bg, bind, break, builtin, caller, cd, command,
       compgen, complete, compopt, continue, declare, dirs, disown, echo,  en-
       able,  eval,  exec,  exit,  export, false, fc, fg, getopts, hash, help,
       history, jobs, kill, let, local, logout, mapfile, popd, printf,  pushd,
       pwd,  read, readonly, return, set, shift, shopt, source, suspend, test,
       times, trap, true, type, typeset, ulimit, umask, unalias, unset, wait -
       bash built-in commands, see bbaasshh(1)

BBAASSHH BBUUIILLTTIINN CCOOMMMMAANNDDSS
       Unless otherwise noted, each builtin command documented in this section
       as accepting options preceded by -- accepts ---- to signify the end of the
       options.  The ::, ttrruuee, ffaallssee, and tteesstt/[[ builtins do not accept options
       and do not treat ---- specially.  The eexxiitt, llooggoouutt, rreettuurrnn,  bbrreeaakk,  ccoonn--
       ttiinnuuee,  lleett,  and sshhiifftt 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.
       :: [_a_r_g_u_m_e_n_t_s]
              No  effect;  the command does nothing beyond expanding _a_r_g_u_m_e_n_t_s
              and performing any specified redirections.  The return status is
              zero.

        ..  _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
       ssoouurrccee _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
              Read and execute commands from _f_i_l_e_n_a_m_e in the current shell en-
              vironment and return the exit status of the  last  command  exe-
              cuted  from  _f_i_l_e_n_a_m_e.   If  _f_i_l_e_n_a_m_e  does not contain a slash,
              filenames in PPAATTHH are used  to  find  the  directory  containing
              _f_i_l_e_n_a_m_e.  The file searched for in PPAATTHH need not be executable.
              When bbaasshh is  not  in  _p_o_s_i_x  _m_o_d_e,  the  current  directory  is
              searched  if no file is found in PPAATTHH.  If the ssoouurrcceeppaatthh option
              to the sshhoopptt builtin command is turned  off,  the  PPAATTHH  is  not
              searched.   If any _a_r_g_u_m_e_n_t_s are supplied, they become the posi-
              tional parameters when _f_i_l_e_n_a_m_e is executed.  Otherwise the  po-
              sitional parameters are unchanged.  If the --TT option is enabled,
              ssoouurrccee inherits any trap on DDEEBBUUGG; if it is not, any DDEEBBUUGG  trap
              string  is  saved  and  restored  around the call to ssoouurrccee, and
              ssoouurrccee unsets the DDEEBBUUGG trap while it executes.  If  --TT  is  not
              set,  and the sourced file changes the DDEEBBUUGG trap, the new value
              is retained when ssoouurrccee completes.  The  return  status  is  the
              status  of  the  last  command exited within the script (0 if no
              commands are executed), and false if _f_i_l_e_n_a_m_e is  not  found  or
              cannot be read.

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

       bbgg [_j_o_b_s_p_e_c ...]
              Resume  each  suspended  job _j_o_b_s_p_e_c in the background, as if it
              had been started with &&.  If _j_o_b_s_p_e_c is not present, the shell's
              notion  of the _c_u_r_r_e_n_t _j_o_b is used.  bbgg _j_o_b_s_p_e_c returns 0 unless
              run when job control is disabled or, when run with  job  control
              enabled,  any  specified  _j_o_b_s_p_e_c  was  not found or was started
              without job control.

       bbiinndd [--mm _k_e_y_m_a_p] [--llppssvvPPSSVVXX]
       bbiinndd [--mm _k_e_y_m_a_p] [--qq _f_u_n_c_t_i_o_n] [--uu _f_u_n_c_t_i_o_n] [--rr _k_e_y_s_e_q]
       bbiinndd [--mm _k_e_y_m_a_p] --ff _f_i_l_e_n_a_m_e
       bbiinndd [--mm _k_e_y_m_a_p] --xx _k_e_y_s_e_q:_s_h_e_l_l_-_c_o_m_m_a_n_d
       bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_f_u_n_c_t_i_o_n_-_n_a_m_e
       bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d
              Display current rreeaaddlliinnee key and function bindings, bind  a  key
              sequence  to  a  rreeaaddlliinnee  function  or macro, or set a rreeaaddlliinnee
              variable.  Each non-option argument is a command as it would ap-
              pear  in _._i_n_p_u_t_r_c, but each binding or command must be passed as
              a separate argument; e.g., '"\C-x\C-r": re-read-init-file'.  Op-
              tions, if supplied, have the following meanings:
              --mm _k_e_y_m_a_p
                     Use _k_e_y_m_a_p as the keymap to be affected by the subsequent
                     bindings.  Acceptable _k_e_y_m_a_p names are _e_m_a_c_s_, _e_m_a_c_s_-_s_t_a_n_-
                     _d_a_r_d_,  _e_m_a_c_s_-_m_e_t_a_,  _e_m_a_c_s_-_c_t_l_x_,  _v_i_, _v_i_-_m_o_v_e_, _v_i_-_c_o_m_m_a_n_d,
                     and _v_i_-_i_n_s_e_r_t.  _v_i is equivalent to  _v_i_-_c_o_m_m_a_n_d  (_v_i_-_m_o_v_e
                     is  also  a  synonym); _e_m_a_c_s is equivalent to _e_m_a_c_s_-_s_t_a_n_-
                     _d_a_r_d.
              --ll     List the names of all rreeaaddlliinnee functions.
              --pp     Display rreeaaddlliinnee function names and bindings  in  such  a
                     way that they can be re-read.
              --PP     List current rreeaaddlliinnee function names and bindings.
              --ss     Display  rreeaaddlliinnee  key  sequences bound to macros and the
                     strings they output in such a way that they  can  be  re-
                     read.
              --SS     Display  rreeaaddlliinnee  key  sequences bound to macros and the
                     strings they output.
              --vv     Display rreeaaddlliinnee variable names and values in such a  way
                     that they can be re-read.
              --VV     List current rreeaaddlliinnee variable names and values.
              --ff _f_i_l_e_n_a_m_e
                     Read key bindings from _f_i_l_e_n_a_m_e.
              --qq _f_u_n_c_t_i_o_n
                     Query about which keys invoke the named _f_u_n_c_t_i_o_n.
              --uu _f_u_n_c_t_i_o_n
                     Unbind all keys bound to the named _f_u_n_c_t_i_o_n.
              --rr _k_e_y_s_e_q
                     Remove any current binding for _k_e_y_s_e_q.
              --xx _k_e_y_s_e_q::_s_h_e_l_l_-_c_o_m_m_a_n_d
                     Cause _s_h_e_l_l_-_c_o_m_m_a_n_d to be executed whenever _k_e_y_s_e_q is en-
                     tered.  When _s_h_e_l_l_-_c_o_m_m_a_n_d is executed,  the  shell  sets
                     the  RREEAADDLLIINNEE__LLIINNEE  variable to the contents of the rreeaadd--
                     lliinnee line buffer and the RREEAADDLLIINNEE__PPOOIINNTT and RREEAADDLLIINNEE__MMAARRKK
                     variables  to the current location of the insertion point
                     and the saved insertion point (the  mark),  respectively.
                     If the executed command changes the value of any of RREEAADD--
                     LLIINNEE__LLIINNEE, RREEAADDLLIINNEE__PPOOIINNTT, or  RREEAADDLLIINNEE__MMAARRKK,  those  new
                     values will be reflected in the editing state.
              --XX     List  all  key  sequences bound to shell commands and the
                     associated commands in a format that can be reused as in-
                     put.

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

       bbrreeaakk [_n]
              Exit from within a ffoorr, wwhhiillee, uunnttiill, or sseelleecctt loop.  If  _n  is
              specified,  break  _n  levels.   _n must be >= 1.  If _n is greater
              than the number of enclosing loops, all enclosing loops are  ex-
              ited.   The  return  value  is 0 unless _n is not greater than or
              equal to 1.

       bbuuiillttiinn _s_h_e_l_l_-_b_u_i_l_t_i_n [_a_r_g_u_m_e_n_t_s]
              Execute the specified shell builtin, passing it  _a_r_g_u_m_e_n_t_s,  and
              return its exit status.  This is useful when defining a function
              whose name is the same as a shell builtin, retaining  the  func-
              tionality of the builtin within the function.  The ccdd builtin is
              commonly redefined this way.  The  return  status  is  false  if
              _s_h_e_l_l_-_b_u_i_l_t_i_n is not a shell builtin command.

       ccaalllleerr [_e_x_p_r]
              Returns the context of any active subroutine call (a shell func-
              tion or a script executed with the .. or ssoouurrccee builtins).  With-
              out _e_x_p_r, ccaalllleerr displays the line number and source filename of
              the current subroutine call.  If a non-negative integer is  sup-
              plied as _e_x_p_r, ccaalllleerr displays the line number, subroutine name,
              and source file corresponding to that position  in  the  current
              execution  call  stack.  This extra information may be used, for
              example, to print a stack trace.  The current frame is frame  0.
              The  return  value is 0 unless the shell is not executing a sub-
              routine call or _e_x_p_r does not correspond to a valid position  in
              the call stack.

       ccdd [--LL|[--PP [--ee]] [-@]] [_d_i_r]
              Change  the  current  directory to _d_i_r.  if _d_i_r is not supplied,
              the value of the HHOOMMEE shell variable is the default.  Any  addi-
              tional arguments following _d_i_r are ignored.  The variable CCDDPPAATTHH
              defines the search path for the directory containing  _d_i_r:  each
              directory  name  in CCDDPPAATTHH is searched for _d_i_r.  Alternative di-
              rectory names in CCDDPPAATTHH are separated by a colon  (:).   A  null
              directory  name  in CCDDPPAATTHH is the same as the current directory,
              i.e., ``..''.  If _d_i_r begins with a slash (/), then CCDDPPAATTHH is not
              used.   The  --PP  option  causes ccdd to use the physical directory
              structure by resolving symbolic links while traversing  _d_i_r  and
              before processing instances of _._. in _d_i_r (see also the --PP option
              to the sseett builtin command); the --LL option forces symbolic links
              to  be followed by resolving the link after processing instances
              of _._. in _d_i_r.  If _._. appears in _d_i_r, it is processed by removing
              the  immediately previous pathname component from _d_i_r, back to a
              slash or the beginning of _d_i_r.  If the  --ee  option  is  supplied
              with  --PP,  and  the current working directory cannot be success-
              fully determined after a successful directory  change,  ccdd  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 $$OOLLDDPPWWDD
              before the directory change is attempted.  If a non-empty direc-
              tory  name  from  CCDDPPAATTHH is used, or if -- is the first argument,
              and the directory change is successful, the absolute pathname of
              the  new  working  directory  is written to the standard output.
              The return value is  true  if  the  directory  was  successfully
              changed; false otherwise.

       ccoommmmaanndd [--ppVVvv] _c_o_m_m_a_n_d [_a_r_g ...]
              Run  _c_o_m_m_a_n_d  with  _a_r_g_s  suppressing  the normal shell function
              lookup.  Only builtin commands or commands found in the PPAATTHH are
              executed.   If the --pp option is given, the search for _c_o_m_m_a_n_d is
              performed using a default value for PPAATTHH that is  guaranteed  to
              find  all of the standard utilities.  If either the --VV or --vv op-
              tion is supplied, a description of _c_o_m_m_a_n_d is printed.   The  --vv
              option  causes  a single word indicating the command or filename
              used to invoke _c_o_m_m_a_n_d to be displayed; the --VV option produces a
              more  verbose  description.  If the --VV or --vv option is supplied,
              the exit status is 0 if _c_o_m_m_a_n_d was found, and  1  if  not.   If
              neither option is supplied and an error occurred or _c_o_m_m_a_n_d can-
              not be found, the exit status is 127.  Otherwise, the exit  sta-
              tus of the ccoommmmaanndd builtin is the exit status of _c_o_m_m_a_n_d.

       ccoommppggeenn [_o_p_t_i_o_n] [_w_o_r_d]
              Generate  possible  completion matches for _w_o_r_d according to the
              _o_p_t_i_o_ns, which may  be  any  option  accepted  by  the  ccoommpplleettee
              builtin  with  the exception of --pp and --rr, and write the matches
              to the standard output.  When using the --FF or  --CC  options,  the
              various  shell  variables set by the programmable completion fa-
              cilities, 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 _w_o_r_d  is  specified,
              only those completions matching _w_o_r_d will be displayed.

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

       ccoommpplleettee [--aabbccddeeffggjjkkssuuvv] [--oo _c_o_m_p_-_o_p_t_i_o_n] [--DDEEII] [--AA _a_c_t_i_o_n] [--GG  _g_l_o_b_-
       _p_a_t] [--WW _w_o_r_d_l_i_s_t]
              [--FF  _f_u_n_c_t_i_o_n]  [--CC _c_o_m_m_a_n_d] [--XX _f_i_l_t_e_r_p_a_t] [--PP _p_r_e_f_i_x] [--SS _s_u_f_-
              _f_i_x] _n_a_m_e [_n_a_m_e _._._.]
       ccoommpplleettee --pprr [--DDEEII] [_n_a_m_e ...]
              Specify how arguments to each _n_a_m_e should be completed.  If  the
              --pp  option  is supplied, or if no options are supplied, existing
              completion specifications are printed in a way that allows  them
              to be reused as input.  The --rr option removes a completion spec-
              ification for each _n_a_m_e, or, if no _n_a_m_es are supplied, all  com-
              pletion specifications.  The --DD option indicates that other sup-
              plied options and actions should apply to the  ``default''  com-
              mand  completion; that is, completion attempted on a command for
              which no completion has previously been defined.  The --EE  option
              indicates  that  other supplied options and actions should apply
              to ``empty'' command completion; that is,  completion  attempted
              on  a  blank  line.  The --II option indicates that other supplied
              options and actions should apply to completion  on  the  initial
              non-assignment  word  on  the line, or after a command delimiter
              such as ;; or ||, which is usually command  name  completion.   If
              multiple  options  are  supplied, the --DD option takes precedence
              over --EE, and both take precedence over --II.  If any of --DD, --EE, or
              --II  are  supplied,  any  other _n_a_m_e arguments are ignored; these
              completions only apply to the case specified by the option.

              The process of applying  these  completion  specifications  when
              word  completion  is attempted is described above under PPrrooggrraamm--
              mmaabbllee CCoommpplleettiioonn.

              Other options, if specified, have the following  meanings.   The
              arguments  to the --GG, --WW, and --XX options (and, if necessary, the
              --PP and --SS options) should be quoted to protect them from  expan-
              sion before the ccoommpplleettee builtin is invoked.
              --oo _c_o_m_p_-_o_p_t_i_o_n
                      The  _c_o_m_p_-_o_p_t_i_o_n  controls  several aspects of the comp-
                      spec's behavior beyond the simple generation of  comple-
                      tions.  _c_o_m_p_-_o_p_t_i_o_n may be one of:
                      bbaasshhddeeffaauulltt
                              Perform the rest of the default bbaasshh completions
                              if the compspec generates no matches.
                      ddeeffaauulltt Use readline's default  filename  completion  if
                              the compspec generates no matches.
                      ddiirrnnaammeess
                              Perform  directory  name completion if the comp-
                              spec generates no matches.
                      ffiilleennaammeess
                              Tell readline that the compspec generates  file-
                              names,  so  it can perform any filename-specific
                              processing (like adding  a  slash  to  directory
                              names,  quoting special characters, or suppress-
                              ing trailing spaces).  Intended to be used  with
                              shell functions.
                      nnooqquuoottee Tell  readline  not to quote the completed words
                              if they are filenames (quoting filenames is  the
                              default).
                      nnoossoorrtt  Tell  readline  not to sort the list of possible
                              completions alphabetically.
                      nnoossppaaccee Tell readline not to append  a  space  (the  de-
                              fault)  to  words  completed  at  the end of the
                              line.
                      pplluussddiirrss
                              After any matches defined by  the  compspec  are
                              generated,  directory  name  completion  is  at-
                              tempted and any matches are added to the results
                              of the other actions.
              --AA _a_c_t_i_o_n
                      The  _a_c_t_i_o_n  may  be  one of the following to generate a
                      list of possible completions:
                      aalliiaass   Alias names.  May also be specified as --aa.
                      aarrrraayyvvaarr
                              Array variable names.
                      bbiinnddiinngg RReeaaddlliinnee key binding names.
                      bbuuiillttiinn Names of shell builtin commands.   May  also  be
                              specified as --bb.
                      ccoommmmaanndd Command names.  May also be specified as --cc.
                      ddiirreeccttoorryy
                              Directory names.  May also be specified as --dd.
                      ddiissaabblleedd
                              Names of disabled shell builtins.
                      eennaabblleedd Names of enabled shell builtins.
                      eexxppoorrtt  Names  of exported shell variables.  May also be
                              specified as --ee.
                      ffiillee    File names.  May also be specified as --ff.
                      ffuunnccttiioonn
                              Names of shell functions.
                      ggrroouupp   Group names.  May also be specified as --gg.
                      hheellppttooppiicc
                              Help topics as accepted by the hheellpp builtin.
                      hhoossttnnaammee
                              Hostnames, as taken from the file  specified  by
                              the HHOOSSTTFFIILLEE shell variable.
                      jjoobb     Job  names,  if job control is active.  May also
                              be specified as --jj.
                      kkeeyywwoorrdd Shell reserved words.  May also be specified  as
                              --kk.
                      rruunnnniinngg Names of running jobs, if job control is active.
                      sseerrvviiccee Service names.  May also be specified as --ss.
                      sseettoopptt  Valid  arguments  for  the  --oo option to the sseett
                              builtin.
                      sshhoopptt   Shell option names  as  accepted  by  the  sshhoopptt
                              builtin.
                      ssiiggnnaall  Signal names.
                      ssttooppppeedd Names of stopped jobs, if job control is active.
                      uusseerr    User names.  May also be specified as --uu.
                      vvaarriiaabbllee
                              Names of all shell variables.  May also be spec-
                              ified as --vv.
              --CC _c_o_m_m_a_n_d
                      _c_o_m_m_a_n_d is executed in a subshell environment,  and  its
                      output is used as the possible completions.
              --FF _f_u_n_c_t_i_o_n
                      The  shell  function _f_u_n_c_t_i_o_n is executed in the current
                      shell environment.  When the function is  executed,  the
                      first argument ($$11) is the name of the command whose ar-
                      guments are being completed, the second argument ($$22) is
                      the word being completed, and the third argument ($$33) is
                      the word preceding the word being completed on the  cur-
                      rent  command line.  When it finishes, the possible com-
                      pletions are retrieved from the value of  the  CCOOMMPPRREEPPLLYY
                      array variable.
              --GG _g_l_o_b_p_a_t
                      The  pathname  expansion  pattern _g_l_o_b_p_a_t is expanded to
                      generate the possible completions.
              --PP _p_r_e_f_i_x
                      _p_r_e_f_i_x is added at the beginning of each  possible  com-
                      pletion after all other options have been applied.
              --SS _s_u_f_f_i_x
                      _s_u_f_f_i_x is appended to each possible completion after all
                      other options have been applied.
              --WW _w_o_r_d_l_i_s_t
                      The _w_o_r_d_l_i_s_t is split using the characters  in  the  IIFFSS
                      special  variable as delimiters, and each resultant word
                      is expanded.  Shell quoting is honored within  _w_o_r_d_l_i_s_t,
                      in order to provide a mechanism for the words to contain
                      shell metacharacters or characters in the value of  IIFFSS.
                      The  possible  completions are the members of the resul-
                      tant list which match the word being completed.
              --XX _f_i_l_t_e_r_p_a_t
                      _f_i_l_t_e_r_p_a_t is a pattern as used for  pathname  expansion.
                      It is applied to the list of possible completions gener-
                      ated by the preceding options and  arguments,  and  each
                      completion  matching _f_i_l_t_e_r_p_a_t is removed from the list.
                      A leading !! in _f_i_l_t_e_r_p_a_t negates the  pattern;  in  this
                      case, any completion not matching _f_i_l_t_e_r_p_a_t is removed.

              The  return  value is true unless an invalid option is supplied,
              an option other than --pp or --rr is supplied without a  _n_a_m_e  argu-
              ment,  an  attempt  is made to remove a completion specification
              for a _n_a_m_e for which no specification exists, or an error occurs
              adding a completion specification.

       ccoommppoopptt [--oo _o_p_t_i_o_n] [--DDEEII] [++oo _o_p_t_i_o_n] [_n_a_m_e]
              Modify  completion  options  for  each _n_a_m_e according to the _o_p_-
              _t_i_o_ns, or for the currently-executing completion if no _n_a_m_es are
              supplied.   If  no _o_p_t_i_o_ns are given, display the completion op-
              tions for each _n_a_m_e or the  current  completion.   The  possible
              values  of  _o_p_t_i_o_n  are those valid for the ccoommpplleettee builtin de-
              scribed above.  The --DD option indicates that other supplied  op-
              tions  should  apply to the ``default'' command completion; that
              is, completion attempted on a command for  which  no  completion
              has previously been defined.  The --EE option indicates that other
              supplied options should apply to ``empty''  command  completion;
              that  is,  completion  attempted on a blank line.  The --II option
              indicates that other supplied options should apply to completion
              on  the initial non-assignment word on the line, or after a com-
              mand delimiter such as ;; or ||, which  is  usually  command  name
              completion.

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

       ccoonnttiinnuuee [_n]
              Resume the next iteration of the enclosing ffoorr, wwhhiillee, uunnttiill, or
              sseelleecctt loop.  If _n is specified, resume  at  the  _nth  enclosing
              loop.   _n  must be >= 1.  If _n is greater than the number of en-
              closing 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.

       ddeeccllaarree [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
       ttyyppeesseett [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
              Declare variables and/or give them attributes.  If no _n_a_m_es  are
              given  then display the values of variables.  The --pp option will
              display the attributes and values of each _n_a_m_e.  When --pp is used
              with  _n_a_m_e  arguments, additional options, other than --ff and --FF,
              are ignored.  When --pp is supplied  without  _n_a_m_e  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  --pp,  ddeeccllaarree  will display the at-
              tributes and values of all shell variables.  The --ff option  will
              restrict the display to shell functions.  The --FF option inhibits
              the display of function definitions; only the function name  and
              attributes are printed.  If the eexxttddeebbuugg shell option is enabled
              using sshhoopptt, the source file name and  line  number  where  each
              _n_a_m_e  is  defined  are displayed as well.  The --FF option implies
              --ff.  The --gg option forces variables to be created or modified at
              the global scope, even when ddeeccllaarree is executed in a shell func-
              tion.  It is ignored in all other cases.  The --II  option  causes
              local  variables  to  inherit the attributes (except the _n_a_m_e_r_e_f
              attribute) and value of any existing variable with the same _n_a_m_e
              at  a  surrounding scope.  If there is no existing variable, the
              local variable is initially unset.  The following options can be
              used  to  restrict output to variables with the specified attri-
              bute or to give variables attributes:
              --aa     Each _n_a_m_e  is  an  indexed  array  variable  (see  AArrrraayyss
                     above).
              --AA     Each  _n_a_m_e  is  an associative array variable (see AArrrraayyss
                     above).
              --ff     Use function names only.
              --ii     The variable is treated as an integer; arithmetic evalua-
                     tion  (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN above) is performed when
                     the variable is assigned a value.
              --ll     When the variable is assigned  a  value,  all  upper-case
                     characters  are  converted to lower-case.  The upper-case
                     attribute is disabled.
              --nn     Give each _n_a_m_e the _n_a_m_e_r_e_f attribute, making  it  a  name
                     reference  to  another  variable.  That other variable is
                     defined by the value of _n_a_m_e.   All  references,  assign-
                     ments,  and attribute modifications to _n_a_m_e, except those
                     using or changing the --nn attribute itself, are  performed
                     on  the variable referenced by _n_a_m_e's value.  The nameref
                     attribute cannot be applied to array variables.
              --rr     Make _n_a_m_es readonly.  These names cannot then be assigned
                     values by subsequent assignment statements or unset.
              --tt     Give each _n_a_m_e the _t_r_a_c_e attribute.  Traced functions in-
                     herit the DDEEBBUUGG and RREETTUURRNN traps from the calling  shell.
                     The trace attribute has no special meaning for variables.
              --uu     When  the  variable  is  assigned a value, all lower-case
                     characters are converted to upper-case.   The  lower-case
                     attribute is disabled.
              --xx     Mark  _n_a_m_es for export to subsequent commands via the en-
                     vironment.

              Using `+' instead of `-' turns off the attribute  instead,  with
              the  exceptions  that ++aa and ++AA may not be used to destroy array
              variables and ++rr will not remove the readonly  attribute.   When
              used in a function, ddeeccllaarree and ttyyppeesseett make each _n_a_m_e local, as
              with the llooccaall command, unless the --gg option is supplied.  If  a
              variable  name  is followed by =_v_a_l_u_e, the value of the variable
              is set to _v_a_l_u_e.  When using --aa or --AA and the  compound  assign-
              ment  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 as-
              sign a value to an array variable without using the compound as-
              signment  syntax  (see  AArrrraayyss above), one of the _n_a_m_e_s is not a
              valid shell variable name, an attempt is made to turn off  read-
              only  status for a readonly variable, an attempt is made to turn
              off array status for an array variable, or an attempt is made to
              display a non-existent function with --ff.

       ddiirrss [[--ccllppvv]] [[++_n]] [[--_n]]
              Without  options,  displays the list of currently remembered di-
              rectories.  The default display is on a single line with  direc-
              tory  names  separated  by spaces.  Directories are added to the
              list with the ppuusshhdd command; the ppooppdd  command  removes  entries
              from the list.  The current directory is always the first direc-
              tory in the stack.
              --cc     Clears the directory stack by deleting  all  of  the  en-
                     tries.
              --ll     Produces  a  listing  using  full  pathnames; the default
                     listing format uses a tilde to denote the home directory.
              --pp     Print the directory stack with one entry per line.
              --vv     Print the directory stack with one entry per  line,  pre-
                     fixing each entry with its index in the stack.
              ++_n     Displays the _nth entry counting from the left of the list
                     shown by ddiirrss when invoked without options, starting with
                     zero.
              --_n     Displays  the  _nth  entry  counting from the right of the
                     list shown by ddiirrss when invoked without options, starting
                     with zero.

              The  return value is 0 unless an invalid option is supplied or _n
              indexes beyond the end of the directory stack.

       ddiissoowwnn [--aarr] [--hh] [_j_o_b_s_p_e_c ... | _p_i_d ... ]
              Without options, remove each _j_o_b_s_p_e_c from the  table  of  active
              jobs.   If _j_o_b_s_p_e_c is not present, and neither the --aa nor the --rr
              option is supplied, the _c_u_r_r_e_n_t _j_o_b is used.  If the  --hh  option
              is  given,  each  _j_o_b_s_p_e_c  is not removed from the table, but is
              marked so that SSIIGGHHUUPP is not sent to the job if  the  shell  re-
              ceives a SSIIGGHHUUPP.  If no _j_o_b_s_p_e_c is supplied, the --aa option means
              to remove or mark all jobs; the --rr option without a _j_o_b_s_p_e_c  ar-
              gument restricts operation to running jobs.  The return value is
              0 unless a _j_o_b_s_p_e_c does not specify a valid job.

       eecchhoo [--nneeEE] [_a_r_g ...]
              Output the _a_r_gs, separated by spaces,  followed  by  a  newline.
              The  return  status  is 0 unless a write error occurs.  If --nn is
              specified, the trailing newline is suppressed.  If the --ee option
              is  given,  interpretation  of  the  following backslash-escaped
              characters is enabled.  The --EE option disables  the  interpreta-
              tion  of these escape characters, even on systems where they are
              interpreted by default.  The xxppgg__eecchhoo shell option may  be  used
              to  dynamically  determine whether or not eecchhoo expands these es-
              cape characters by default.  eecchhoo does not interpret ---- to  mean
              the  end  of  options.  eecchhoo interprets the following escape se-
              quences:
              \\aa     alert (bell)
              \\bb     backspace
              \\cc     suppress further output
              \\ee
              \\EE     an escape character
              \\ff     form feed
              \\nn     new line
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\\\     backslash
              \\00_n_n_n  the eight-bit character whose value is  the  octal  value
                     _n_n_n (zero to three octal digits)
              \\xx_H_H   the  eight-bit  character  whose value is the hexadecimal
                     value _H_H (one or two hex digits)
              \\uu_H_H_H_H the Unicode (ISO/IEC 10646) character whose value is  the
                     hexadecimal value _H_H_H_H (one to four hex digits)
              \\UU_H_H_H_H_H_H_H_H
                     the  Unicode (ISO/IEC 10646) character whose value is the
                     hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits)

       eennaabbllee [--aa] [--ddnnppss] [--ff _f_i_l_e_n_a_m_e] [_n_a_m_e ...]
              Enable and disable builtin shell commands.  Disabling a  builtin
              allows a disk command which has the same name as a shell builtin
              to be executed without specifying a full pathname,  even  though
              the  shell  normally searches for builtins before disk commands.
              If --nn is used, each _n_a_m_e is disabled; otherwise, _n_a_m_e_s  are  en-
              abled.   For  example, to use the tteesstt binary found via the PPAATTHH
              instead of the shell builtin version, run  ``enable  -n  test''.
              The  --ff  option  means to load the new builtin command _n_a_m_e from
              shared object _f_i_l_e_n_a_m_e, on systems that support dynamic loading.
              The  --dd  option will delete a builtin previously loaded with --ff.
              If no _n_a_m_e arguments are given, or if the --pp option is supplied,
              a list of shell builtins is printed.  With no other option argu-
              ments, the list consists of all enabled shell builtins.   If  --nn
              is  supplied, only disabled builtins are printed.  If --aa is sup-
              plied, the list printed includes all builtins, with  an  indica-
              tion  of whether or not each is enabled.  If --ss is supplied, the
              output is restricted to the POSIX _s_p_e_c_i_a_l builtins.  The  return
              value  is  0 unless a _n_a_m_e is not a shell builtin or there is an
              error loading a new builtin from a shared object.

       eevvaall [_a_r_g ...]
              The _a_r_gs are read and concatenated together into a  single  com-
              mand.   This command is then read and executed by the shell, and
              its exit status is returned as the value of eevvaall.  If there  are
              no _a_r_g_s, or only null arguments, eevvaall returns 0.

       eexxeecc [--ccll] [--aa _n_a_m_e] [_c_o_m_m_a_n_d [_a_r_g_u_m_e_n_t_s]]
              If  _c_o_m_m_a_n_d is specified, it replaces the shell.  No new process
              is created.  The _a_r_g_u_m_e_n_t_s become the arguments to _c_o_m_m_a_n_d.   If
              the --ll option is supplied, the shell places a dash at the begin-
              ning of the zeroth argument passed to _c_o_m_m_a_n_d.  This is what _l_o_-
              _g_i_n(1)  does.   The --cc option causes _c_o_m_m_a_n_d to be executed with
              an empty environment.  If --aa is supplied, the shell passes  _n_a_m_e
              as the zeroth argument to the executed command.  If _c_o_m_m_a_n_d can-
              not be executed for some reason, a non-interactive shell  exits,
              unless  the  eexxeeccffaaiill shell option is enabled.  In that case, it
              returns failure.  An interactive shell returns  failure  if  the
              file  cannot  be  executed.  A subshell exits unconditionally if
              eexxeecc fails.  If _c_o_m_m_a_n_d is not specified, any redirections  take
              effect  in  the  current  shell, and the return status is 0.  If
              there is a redirection error, the return status is 1.

       eexxiitt [_n]
              Cause the shell to exit with a status of _n.  If  _n  is  omitted,
              the exit status is that of the last command executed.  A trap on
              EEXXIITT is executed before the shell terminates.

       eexxppoorrtt [--ffnn] [_n_a_m_e[=_w_o_r_d]] ...
       eexxppoorrtt --pp
              The supplied _n_a_m_e_s are marked for automatic export to the  envi-
              ronment  of subsequently executed commands.  If the --ff option is
              given, the _n_a_m_e_s refer to functions.  If no _n_a_m_e_s are given,  or
              if  the  --pp  option is supplied, a list of names of all exported
              variables is printed.  The --nn option causes the export  property
              to be removed from each _n_a_m_e.  If a variable name is followed by
              =_w_o_r_d, the value of the variable is set to _w_o_r_d.  eexxppoorrtt returns
              an exit status of 0 unless an invalid option is encountered, one
              of the _n_a_m_e_s is not a valid shell variable name, or --ff  is  sup-
              plied with a _n_a_m_e that is not a function.

       ffcc [--ee _e_n_a_m_e] [--llnnrr] [_f_i_r_s_t] [_l_a_s_t]
       ffcc --ss [_p_a_t=_r_e_p] [_c_m_d]
              The  first  form  selects a range of commands from _f_i_r_s_t to _l_a_s_t
              from the history list and  displays  or  edits  and  re-executes
              them.   _F_i_r_s_t  and  _l_a_s_t may be specified as a string (to locate
              the last command beginning with that string) or as a number  (an
              index  into the history list, where a negative number is used as
              an offset from the current command  number).   When  listing,  a
              _f_i_r_s_t  or  _l_a_s_t of 0 is equivalent to -1 and -0 is equivalent to
              the current command (usually the ffcc  command);  otherwise  0  is
              equivalent  to  -1 and -0 is invalid.  If _l_a_s_t is not specified,
              it is set to the current command for listing (so  that  ``fc  -l
              -10''  prints  the last 10 commands) and to _f_i_r_s_t otherwise.  If
              _f_i_r_s_t is not specified, it is set to the  previous  command  for
              editing and -16 for listing.

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

              In the second form, _c_o_m_m_a_n_d is re-executed after  each  instance
              of  _p_a_t  is replaced by _r_e_p.  _C_o_m_m_a_n_d is interpreted the same as
              _f_i_r_s_t 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  in-
              valid  option  is  encountered  or _f_i_r_s_t or _l_a_s_t specify history
              lines out of range.  If the --ee option is  supplied,  the  return
              value is the value of the last command executed or failure if an
              error occurs with the temporary file of commands.  If the second
              form  is  used, the return status is that of the command re-exe-
              cuted, unless _c_m_d does not specify  a  valid  history  line,  in
              which case ffcc returns failure.

       ffgg [_j_o_b_s_p_e_c]
              Resume  _j_o_b_s_p_e_c  in the foreground, and make it the current job.
              If _j_o_b_s_p_e_c is not present, the shell's notion of the _c_u_r_r_e_n_t _j_o_b
              is  used.   The  return value is that of the command placed into
              the foreground, or failure if run when job control  is  disabled
              or, when run with job control enabled, if _j_o_b_s_p_e_c does not spec-
              ify a valid job or _j_o_b_s_p_e_c specifies  a  job  that  was  started
              without job control.

       ggeettooppttss _o_p_t_s_t_r_i_n_g _n_a_m_e [_a_r_g _._._.]
              ggeettooppttss  is used by shell procedures to parse positional parame-
              ters.  _o_p_t_s_t_r_i_n_g contains the option  characters  to  be  recog-
              nized;  if a character is followed by a colon, the option is ex-
              pected to have an argument, which should be separated from it by
              white  space.  The colon and question mark characters may not be
              used as option characters.  Each time  it  is  invoked,  ggeettooppttss
              places  the next option in the shell variable _n_a_m_e, initializing
              _n_a_m_e if it does not exist, and the index of the next argument to
              be processed into the variable OOPPTTIINNDD.  OOPPTTIINNDD is initialized to
              1 each time the shell or a shell script is invoked.  When an op-
              tion requires an argument, ggeettooppttss places that argument into the
              variable OOPPTTAARRGG.  The shell does not reset OOPPTTIINNDD automatically;
              it  must  be  manually  reset  between multiple calls to ggeettooppttss
              within the same shell invocation if a new set of  parameters  is
              to be used.

              When the end of options is encountered, ggeettooppttss exits with a re-
              turn value greater than zero.  OOPPTTIINNDD is set to the index of the
              first non-option argument, and _n_a_m_e is set to ?.

              ggeettooppttss  normally  parses the positional parameters, but if more
              arguments are supplied as _a_r_g values, ggeettooppttss parses  those  in-
              stead.

              ggeettooppttss  can  report errors in two ways.  If the first character
              of _o_p_t_s_t_r_i_n_g is a colon, _s_i_l_e_n_t error  reporting  is  used.   In
              normal  operation,  diagnostic messages are printed when invalid
              options or missing option arguments  are  encountered.   If  the
              variable  OOPPTTEERRRR  is  set  to  0, no error messages will be dis-
              played, even if the first character of _o_p_t_s_t_r_i_n_g is not a colon.

              If an invalid option is seen, ggeettooppttss places ? into _n_a_m_e and, if
              not  silent,  prints  an  error  message  and unsets OOPPTTAARRGG.  If
              ggeettooppttss is silent, the option character found is placed  in  OOPP--
              TTAARRGG and no diagnostic message is printed.

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

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

       hhaasshh [--llrr] [--pp _f_i_l_e_n_a_m_e] [--ddtt] [_n_a_m_e]
              Each time hhaasshh is invoked, the full pathname of the command _n_a_m_e
              is determined by searching the directories in $$PPAATTHH  and  remem-
              bered.  Any previously-remembered pathname is discarded.  If the
              --pp option is supplied, no path search is performed, and _f_i_l_e_n_a_m_e
              is  used  as  the  full  filename of the command.  The --rr option
              causes the shell to forget all remembered locations.  The --dd op-
              tion  causes the shell to forget the remembered location of each
              _n_a_m_e.  If the --tt option is supplied, the full pathname to  which
              each  _n_a_m_e  corresponds  is printed.  If multiple _n_a_m_e arguments
              are supplied with --tt, the _n_a_m_e is printed before the hashed full
              pathname.  The --ll option causes output to be displayed in a for-
              mat that may be reused as input.  If no arguments are given,  or
              if only --ll is supplied, information about remembered commands is
              printed.  The return status is true unless a _n_a_m_e is  not  found
              or an invalid option is supplied.

       hheellpp [--ddmmss] [_p_a_t_t_e_r_n]
              Display  helpful information about builtin commands.  If _p_a_t_t_e_r_n
              is specified, hheellpp gives detailed help on all commands  matching
              _p_a_t_t_e_r_n;  otherwise  help for all the builtins and shell control
              structures is printed.
              --dd     Display a short description of each _p_a_t_t_e_r_n
              --mm     Display the description of each _p_a_t_t_e_r_n in a manpage-like
                     format
              --ss     Display only a short usage synopsis for each _p_a_t_t_e_r_n

              The return status is 0 unless no command matches _p_a_t_t_e_r_n.

       hhiissttoorryy [[_n]]
       hhiissttoorryy --cc
       hhiissttoorryy --dd _o_f_f_s_e_t
       hhiissttoorryy --dd _s_t_a_r_t-_e_n_d
       hhiissttoorryy --aannrrww [_f_i_l_e_n_a_m_e]
       hhiissttoorryy --pp _a_r_g [_a_r_g _._._.]
       hhiissttoorryy --ss _a_r_g [_a_r_g _._._.]
              With no options, display the command history list with line num-
              bers.  Lines listed with a ** have been modified.  An argument of
              _n  lists only the last _n lines.  If the shell variable HHIISSTTTTIIMMEE--
              FFOORRMMAATT is set and not null, it is used as a  format  string  for
              _s_t_r_f_t_i_m_e(3)  to display the time stamp associated with each dis-
              played history entry.  No intervening blank is  printed  between
              the  formatted  time stamp and the history line.  If _f_i_l_e_n_a_m_e is
              supplied, it is used as the name of the history  file;  if  not,
              the  value  of HHIISSTTFFIILLEE is used.  Options, if supplied, have the
              following meanings:
              --cc     Clear the history list by deleting all the entries.
              --dd _o_f_f_s_e_t
                     Delete the history entry at position _o_f_f_s_e_t.   If  _o_f_f_s_e_t
                     is negative, it is interpreted as relative to one greater
                     than the last history position, so negative indices count
                     back  from  the  end  of  the history, and an index of -1
                     refers to the current hhiissttoorryy --dd command.
              --dd _s_t_a_r_t-_e_n_d
                     Delete the history entries between  positions  _s_t_a_r_t  and
                     _e_n_d,  inclusive.   Positive and negative values for _s_t_a_r_t
                     and _e_n_d are interpreted as described above.
              --aa     Append the ``new'' history lines  to  the  history  file.
                     These  are  history  lines entered since the beginning of
                     the current bbaasshh session, but not already appended to the
                     history file.
              --nn     Read  the history lines not already read from the history
                     file into the current history list.  These are lines  ap-
                     pended  to  the  history  file since the beginning of the
                     current bbaasshh session.
              --rr     Read the contents of the history file and append them  to
                     the current history list.
              --ww     Write the current history list to the history file, over-
                     writing the history file's contents.
              --pp     Perform history substitution on the  following  _a_r_g_s  and
                     display  the  result  on  the  standard output.  Does not
                     store the results in the history list.  Each _a_r_g must  be
                     quoted to disable normal history expansion.
              --ss     Store  the  _a_r_g_s  in  the history list as a single entry.
                     The last command in the history list  is  removed  before
                     the _a_r_g_s are added.

              If  the  HHIISSTTTTIIMMEEFFOORRMMAATT 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 _o_f_f_s_e_t  is  sup-
              plied as an argument to --dd, or the history expansion supplied as
              an argument to --pp fails.

       jjoobbss [--llnnpprrss] [ _j_o_b_s_p_e_c ... ]
       jjoobbss --xx _c_o_m_m_a_n_d [ _a_r_g_s ... ]
              The first form lists the active jobs.  The options have the fol-
              lowing meanings:
              --ll     List process IDs in addition to the normal information.
              --nn     Display  information  only  about  jobs that have changed
                     status since the user was last notified of their status.
              --pp     List only the process  ID  of  the  job's  process  group
                     leader.
              --rr     Display only running jobs.
              --ss     Display only stopped jobs.

              If  _j_o_b_s_p_e_c  is given, output is restricted to information about
              that job.  The return status is 0 unless an  invalid  option  is
              encountered or an invalid _j_o_b_s_p_e_c is supplied.

              If the --xx option is supplied, jjoobbss replaces any _j_o_b_s_p_e_c found in
              _c_o_m_m_a_n_d or _a_r_g_s with the corresponding process group ID, and ex-
              ecutes _c_o_m_m_a_n_d passing it _a_r_g_s, returning its exit status.

       kkiillll [--ss _s_i_g_s_p_e_c | --nn _s_i_g_n_u_m | --_s_i_g_s_p_e_c] [_p_i_d | _j_o_b_s_p_e_c] ...
       kkiillll --ll|--LL [_s_i_g_s_p_e_c | _e_x_i_t___s_t_a_t_u_s]
              Send  the  signal  named  by  _s_i_g_s_p_e_c or _s_i_g_n_u_m to the processes
              named by _p_i_d or _j_o_b_s_p_e_c.  _s_i_g_s_p_e_c is either  a  case-insensitive
              signal  name such as SSIIGGKKIILLLL (with or without the SSIIGG prefix) or
              a signal number; _s_i_g_n_u_m is a signal number.  If _s_i_g_s_p_e_c  is  not
              present,  then  SSIIGGTTEERRMM is assumed.  An argument of --ll lists the
              signal names.  If any arguments are supplied when --ll  is  given,
              the  names  of  the  signals  corresponding to the arguments are
              listed, and the return status is 0.  The _e_x_i_t___s_t_a_t_u_s argument to
              --ll  is  a  number  specifying either a signal number or the exit
              status of a process terminated by a signal.  The  --LL  option  is
              equivalent  to --ll.  kkiillll returns true if at least one signal was
              successfully sent, or false if an error occurs or an invalid op-
              tion is encountered.

       lleett _a_r_g [_a_r_g ...]
              Each _a_r_g is an arithmetic expression to be evaluated (see AARRIITTHH--
              MMEETTIICC EEVVAALLUUAATTIIOONN above).  If the last _a_r_g evaluates  to  0,  lleett
              returns 1; 0 is returned otherwise.

       llooccaall [_o_p_t_i_o_n] [_n_a_m_e[=_v_a_l_u_e] ... | - ]
              For  each  argument, a local variable named _n_a_m_e is created, and
              assigned _v_a_l_u_e.  The _o_p_t_i_o_n can be any of the  options  accepted
              by ddeeccllaarree.  When llooccaall is used within a function, it causes the
              variable _n_a_m_e to have a visible scope restricted to  that  func-
              tion  and  its children.  If _n_a_m_e is -, the set of shell options
              is made local to the function in which llooccaall is  invoked:  shell
              options  changed  using  the sseett builtin inside the function are
              restored to their original values  when  the  function  returns.
              The restore is effected as if a series of sseett commands were exe-
              cuted to restore the values that were in place before the  func-
              tion.   With no operands, llooccaall writes a list of local variables
              to the standard output.  It is an error to use  llooccaall  when  not
              within  a function.  The return status is 0 unless llooccaall is used
              outside a function, an invalid _n_a_m_e is supplied, or  _n_a_m_e  is  a
              readonly variable.

       llooggoouutt Exit a login shell.

       mmaappffiillee  [--dd  _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC
       _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y]
       rreeaaddaarrrraayy [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC
       _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y]
              Read  lines from the standard input into the indexed array vari-
              able _a_r_r_a_y, or from file descriptor _f_d if the --uu option is  sup-
              plied.   The variable MMAAPPFFIILLEE is the default _a_r_r_a_y.  Options, if
              supplied, have the following meanings:
              --dd     The first character of _d_e_l_i_m is used  to  terminate  each
                     input  line,  rather than newline.  If _d_e_l_i_m is the empty
                     string, mmaappffiillee will terminate a line when it reads a NUL
                     character.
              --nn     Copy  at  most _c_o_u_n_t lines.  If _c_o_u_n_t is 0, all lines are
                     copied.
              --OO     Begin assigning to _a_r_r_a_y at index  _o_r_i_g_i_n.   The  default
                     index is 0.
              --ss     Discard the first _c_o_u_n_t lines read.
              --tt     Remove  a trailing _d_e_l_i_m (default newline) from each line
                     read.
              --uu     Read lines from file descriptor _f_d instead of  the  stan-
                     dard input.
              --CC     Evaluate  _c_a_l_l_b_a_c_k each time _q_u_a_n_t_u_m lines are read.  The
                     --cc option specifies _q_u_a_n_t_u_m.
              --cc     Specify the number of lines read  between  each  call  to
                     _c_a_l_l_b_a_c_k.

              If  --CC  is  specified  without  --cc, the default quantum is 5000.
              When _c_a_l_l_b_a_c_k 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.  _c_a_l_l_b_a_c_k  is  evaluated  after
              the line is read but before the array element is assigned.

              If  not supplied with an explicit origin, mmaappffiillee will clear _a_r_-
              _r_a_y before assigning to it.

              mmaappffiillee returns successfully unless an invalid option or  option
              argument  is  supplied,  _a_r_r_a_y is invalid or unassignable, or if
              _a_r_r_a_y is not an indexed array.

       ppooppdd [-nn] [+_n] [-_n]
              Removes entries from the directory stack.   With  no  arguments,
              removes  the  top directory from the stack, and performs a ccdd to
              the new top directory.  Arguments, if supplied, have the follow-
              ing meanings:
              --nn     Suppresses  the  normal change of directory when removing
                     directories from the stack, so that only the stack is ma-
                     nipulated.
              ++_n     Removes  the _nth entry counting from the left of the list
                     shown by ddiirrss, starting with zero.  For  example:  ``popd
                     +0'' removes the first directory, ``popd +1'' the second.
              --_n     Removes the _nth entry counting from the right of the list
                     shown by ddiirrss, starting with zero.  For  example:  ``popd
                     -0''  removes the last directory, ``popd -1'' the next to
                     last.

              If the ppooppdd command is successful, a ddiirrss is performed as  well,
              and  the  return  status is 0.  ppooppdd returns false if an invalid
              option is encountered, the directory stack is empty, a non-exis-
              tent directory stack entry is specified, or the directory change
              fails.

       pprriinnttff [--vv _v_a_r] _f_o_r_m_a_t [_a_r_g_u_m_e_n_t_s]
              Write the formatted _a_r_g_u_m_e_n_t_s to the standard output  under  the
              control  of  the  _f_o_r_m_a_t.  The --vv option causes the output to be
              assigned to the variable _v_a_r rather than being  printed  to  the
              standard output.

              The  _f_o_r_m_a_t  is a character string which contains three types of
              objects: plain characters, which are simply copied  to  standard
              output,  character  escape  sequences,  which  are converted and
              copied to the standard output, and format  specifications,  each
              of  which  causes  printing of the next successive _a_r_g_u_m_e_n_t.  In
              addition to the standard _p_r_i_n_t_f(1) format specifications, pprriinnttff
              interprets the following extensions:
              %%bb     causes pprriinnttff to expand backslash escape sequences in the
                     corresponding _a_r_g_u_m_e_n_t in the same way as eecchhoo --ee.
              %%qq     causes pprriinnttff to output the corresponding _a_r_g_u_m_e_n_t  in  a
                     format that can be reused as shell input.
              %%((_d_a_t_e_f_m_t))TT
                     causes  pprriinnttff  to  output the date-time string resulting
                     from using _d_a_t_e_f_m_t as a format  string  for  _s_t_r_f_t_i_m_e(3).
                     The corresponding _a_r_g_u_m_e_n_t 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  ar-
                     gument is specified, conversion behaves as if -1 had been
                     given.  This is an exception to the usual  pprriinnttff  behav-
                     ior.

              The %b, %q, and %T directives all use the field width and preci-
              sion arguments from the format specification and write that many
              bytes from (or use that wide a field for) the expanded argument,
              which usually contains more characters than the original.

              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  _f_o_r_m_a_t  is  reused as necessary to consume all of the _a_r_g_u_-
              _m_e_n_t_s.  If the _f_o_r_m_a_t requires more _a_r_g_u_m_e_n_t_s than are supplied,
              the  extra  format  specifications  behave as if a zero value or
              null string, as appropriate,  had  been  supplied.   The  return
              value is zero on success, non-zero on failure.

       ppuusshhdd [--nn] [+_n] [-_n]
       ppuusshhdd [--nn] [_d_i_r]
              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, ppuusshhdd exchanges the top two di-
              rectories and returns 0, unless the directory  stack  is  empty.
              Arguments, if supplied, have the following meanings:
              --nn     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  ddiirrss,  starting  with
                     zero) is at the top.
              --_n     Rotates  the  stack  so  that the _nth directory (counting
                     from the right of the list shown by ddiirrss,  starting  with
                     zero) is at the top.
              _d_i_r    Adds _d_i_r 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 ccdd builtin.

              If the ppuusshhdd command is successful, a ddiirrss is performed as well.
              If the first form is used, ppuusshhdd returns 0 unless the cd to  _d_i_r
              fails.   With the second form, ppuusshhdd returns 0 unless the direc-
              tory stack is empty, a non-existent directory stack  element  is
              specified,  or the directory change to the specified new current
              directory fails.

       ppwwdd [--LLPP]
              Print the absolute pathname of the  current  working  directory.
              The pathname printed contains no symbolic links if the --PP option
              is supplied or the --oo pphhyyssiiccaall option to the sseett builtin command
              is  enabled.  If the --LL option is used, the pathname printed may
              contain symbolic links.  The return status is 0 unless an  error
              occurs while reading the name of the current directory or an in-
              valid option is supplied.

       rreeaadd [--eerrss] [--aa _a_n_a_m_e] [--dd _d_e_l_i_m] [--ii _t_e_x_t] [--nn _n_c_h_a_r_s] [--NN _n_c_h_a_r_s] [--pp
       _p_r_o_m_p_t] [--tt _t_i_m_e_o_u_t] [--uu _f_d] [_n_a_m_e ...]
              One  line  is read from the standard input, or from the file de-
              scriptor _f_d supplied as an argument to the --uu option, split into
              words  as  described  above  under WWoorrdd SSpplliittttiinngg, and the first
              word is assigned to the first _n_a_m_e, the second word to the  sec-
              ond  _n_a_m_e,  and  so on.  If there are more words than names, the
              remaining words and their intervening delimiters are assigned to
              the  last  _n_a_m_e.   If  there are fewer words read from the input
              stream than names, the remaining names are assigned  empty  val-
              ues.   The  characters  in  IIFFSS  are used to split the line into
              words using the same rules the shell  uses  for  expansion  (de-
              scribed  above  under  WWoorrdd SSpplliittttiinngg).  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:
              --aa _a_n_a_m_e
                     The words are assigned to sequential indices of the array
                     variable _a_n_a_m_e, starting at 0.  _a_n_a_m_e is unset before any
                     new values are assigned.  Other _n_a_m_e  arguments  are  ig-
                     nored.
              --dd _d_e_l_i_m
                     The first character of _d_e_l_i_m is used to terminate the in-
                     put line, rather than newline.  If  _d_e_l_i_m  is  the  empty
                     string,  rreeaadd  will  terminate a line when it reads a NUL
                     character.
              --ee     If the standard input is coming from a terminal, rreeaaddlliinnee
                     (see  RREEAADDLLIINNEE  above) is used to obtain the line.  Read-
                     line uses the current (or default, if  line  editing  was
                     not  previously  active) editing settings, but uses Read-
                     line's default filename completion.
              --ii _t_e_x_t
                     If rreeaaddlliinnee is being used  to  read  the  line,  _t_e_x_t  is
                     placed into the editing buffer before editing begins.
              --nn _n_c_h_a_r_s
                     rreeaadd  returns after reading _n_c_h_a_r_s characters rather than
                     waiting for a complete line of input, but honors a delim-
                     iter  if fewer than _n_c_h_a_r_s characters are read before the
                     delimiter.
              --NN _n_c_h_a_r_s
                     rreeaadd returns  after  reading  exactly  _n_c_h_a_r_s  characters
                     rather  than waiting for a complete line of input, unless
                     EOF is encountered or rreeaadd times out.  Delimiter  charac-
                     ters  encountered  in the input are not treated specially
                     and do not cause rreeaadd to return until  _n_c_h_a_r_s  characters
                     are  read.   The result is not split on the characters in
                     IIFFSS; the intent is that the variable is assigned  exactly
                     the characters read (with the exception of backslash; see
                     the --rr option below).
              --pp _p_r_o_m_p_t
                     Display _p_r_o_m_p_t on standard error, without a trailing new-
                     line, before attempting to read any input.  The prompt is
                     displayed only if input is coming from a terminal.
              --rr     Backslash does not act as an escape character.  The back-
                     slash  is considered to be part of the line.  In particu-
                     lar, a backslash-newline pair may not then be used  as  a
                     line continuation.
              --ss     Silent mode.  If input is coming from a terminal, charac-
                     ters are not echoed.
              --tt _t_i_m_e_o_u_t
                     Cause rreeaadd to time out and return failure if  a  complete
                     line  of  input  (or a specified number of characters) is
                     not read within _t_i_m_e_o_u_t seconds.  _t_i_m_e_o_u_t may be a  deci-
                     mal  number with a fractional portion following the deci-
                     mal point.  This option is  only  effective  if  rreeaadd  is
                     reading  input  from  a  terminal, pipe, or other special
                     file; it has no effect when reading from  regular  files.
                     If rreeaadd times out, rreeaadd saves any partial input read into
                     the specified variable _n_a_m_e.  If _t_i_m_e_o_u_t is 0,  rreeaadd  re-
                     turns  immediately, without trying to read any data.  The
                     exit status is 0 if input is available on  the  specified
                     file  descriptor, non-zero otherwise.  The exit status is
                     greater than 128 if the timeout is exceeded.
              --uu _f_d  Read input from file descriptor _f_d.

              If no _n_a_m_e_s are supplied, the line read, without the ending  de-
              limiter  but  otherwise  unmodified, is assigned to the variable
              RREEPPLLYY.  The exit status is zero, unless end-of-file  is  encoun-
              tered,  rreeaadd times out (in which case the status is greater than
              128), a variable assignment error (such as assigning to a  read-
              only variable) occurs, or an invalid file descriptor is supplied
              as the argument to --uu.

       rreeaaddoonnllyy [--aaAAff] [--pp] [_n_a_m_e[=_w_o_r_d] ...]
              The given _n_a_m_e_s are marked readonly; the values of  these  _n_a_m_e_s
              may  not  be changed by subsequent assignment.  If the --ff option
              is supplied, the functions corresponding to  the  _n_a_m_e_s  are  so
              marked.   The  --aa  option restricts the variables to indexed ar-
              rays; the --AA option restricts the variables to  associative  ar-
              rays.  If both options are supplied, --AA takes precedence.  If no
              _n_a_m_e arguments are given, or if the --pp  option  is  supplied,  a
              list of all readonly names is printed.  The other options may be
              used to restrict the output to a subset of the set  of  readonly
              names.   The --pp option causes output to be displayed in a format
              that may be reused as input.  If a variable name is followed  by
              =_w_o_r_d,  the  value  of  the variable is set to _w_o_r_d.  The return
              status is 0 unless an invalid option is encountered, one of  the
              _n_a_m_e_s is not a valid shell variable name, or --ff is supplied with
              a _n_a_m_e that is not a function.

       rreettuurrnn [_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  rree--
              ttuurrnn is executed by a trap handler, the last command used to de-
              termine the status is the last command executed before the  trap
              handler.   If  rreettuurrnn  is executed during a DDEEBBUUGG trap, the last
              command used to determine the status is the  last  command  exe-
              cuted  by the trap handler before rreettuurrnn was invoked.  If rreettuurrnn
              is used outside a function, but during execution of a script  by
              the  ..   (ssoouurrccee) command, it causes the shell to stop executing
              that script and return either _n or the exit status of  the  last
              command  executed  within  the  script as the exit status of the
              script.  If _n is supplied, the return value is its least signif-
              icant  8  bits.  The return status is non-zero if rreettuurrnn is sup-
              plied a non-numeric argument, or is used outside a function  and
              not  during  execution  of a script by .. or ssoouurrccee.  Any command
              associated with the RREETTUURRNN trap is executed before execution re-
              sumes after the function or script.

       sseett [----aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [--oo _o_p_t_i_o_n_-_n_a_m_e] [_a_r_g ...]
       sseett [++aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [++oo _o_p_t_i_o_n_-_n_a_m_e] [_a_r_g ...]
              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 _p_o_s_i_x _m_o_d_e, only shell variables  are  listed.
              The  output is sorted according to the current locale.  When op-
              tions 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
              $$11,  $$22,  ......   $$_n.   Options,  if specified, have the following
              meanings:
              --aa      Each variable or function that is created or modified is
                      given  the export attribute and marked for export to the
                      environment of subsequent commands.
              --bb      Report the status of terminated background jobs  immedi-
                      ately, rather than before the next primary prompt.  This
                      is effective only when job control is enabled.
              --ee      Exit immediately if a _p_i_p_e_l_i_n_e (which may consist  of  a
                      single  _s_i_m_p_l_e  _c_o_m_m_a_n_d),  a _l_i_s_t, or a _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d
                      (see SSHHEELLLL GGRRAAMMMMAARR above), exits with a non-zero status.
                      The  shell  does  not  exit if the command that fails is
                      part of the command list immediately following  a  wwhhiillee
                      or  uunnttiill  keyword, part of the test following the iiff or
                      eelliiff 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 --ee was being
                      ignored, the shell does not exit.  A  trap  on  EERRRR,  if
                      set,  is  executed  before the shell exits.  This option
                      applies to the shell environment and each subshell envi-
                      ronment  separately  (see  CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT
                      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 --ee is being ignored, none of the  commands
                      executed  within  the  compound command or function body
                      will be affected by the --ee setting, even if  --ee  is  set
                      and  a  command returns a failure status.  If a compound
                      command or shell function sets --ee while executing  in  a
                      context  where --ee is ignored, that setting will not have
                      any effect until the compound  command  or  the  command
                      containing the function call completes.
              --ff      Disable pathname expansion.
              --hh      Remember  the location of commands as they are looked up
                      for execution.  This is enabled by default.
              --kk      All arguments in the form of assignment  statements  are
                      placed  in the environment for a command, not just those
                      that precede the command name.
              --mm      Monitor mode.  Job control is enabled.  This  option  is
                      on  by  default  for  interactive shells on systems that
                      support it (see JJOOBB CCOONNTTRROOLL above).  All  processes  run
                      in a separate process group.  When a background job com-
                      pletes, the shell prints a line containing its exit sta-
                      tus.
              --nn      Read commands but do not execute them.  This may be used
                      to check a shell script for syntax errors.  This is  ig-
                      nored by interactive shells.
              --oo _o_p_t_i_o_n_-_n_a_m_e
                      The _o_p_t_i_o_n_-_n_a_m_e can be one of the following:
                      aalllleexxppoorrtt
                              Same as --aa.
                      bbrraacceeeexxppaanndd
                              Same as --BB.
                      eemmaaccss   Use  an  emacs-style command line editing inter-
                              face.  This is enabled by default when the shell
                              is interactive, unless the shell is started with
                              the ----nnooeeddiittiinngg option.  This also  affects  the
                              editing interface used for rreeaadd --ee.
                      eerrrreexxiitt Same as --ee.
                      eerrrrttrraaccee
                              Same as --EE.
                      ffuunnccttrraaccee
                              Same as --TT.
                      hhaasshhaallll Same as --hh.
                      hhiisstteexxppaanndd
                              Same as --HH.
                      hhiissttoorryy Enable command history, as described above under
                              HHIISSTTOORRYY.  This option is on by default in inter-
                              active shells.
                      iiggnnoorreeeeooff
                              The  effect  is  as  if  the shell command ``IG-
                              NOREEOF=10'' had been executed (see SShheellll  VVaarrii--
                              aabblleess above).
                      kkeeyywwoorrdd Same as --kk.
                      mmoonniittoorr Same as --mm.
                      nnoocclloobbbbeerr
                              Same as --CC.
                      nnooeexxeecc  Same as --nn.
                      nnoogglloobb  Same as --ff.
                      nnoolloogg   Currently ignored.
                      nnoottiiffyy  Same as --bb.
                      nnoouunnsseett Same as --uu.
                      oonneeccmmdd  Same as --tt.
                      pphhyyssiiccaall
                              Same as --PP.
                      ppiippeeffaaiill
                              If  set,  the  return value of a pipeline is the
                              value of the last (rightmost)  command  to  exit
                              with  a non-zero status, or zero if all commands
                              in the pipeline exit successfully.  This  option
                              is disabled by default.
                      ppoossiixx   Change  the  behavior  of bbaasshh where the default
                              operation differs from  the  POSIX  standard  to
                              match  the  standard (_p_o_s_i_x _m_o_d_e).  See SSEEEE AALLSSOO
                              below for a reference to a document that details
                              how posix mode affects bash's behavior.
                      pprriivviilleeggeedd
                              Same as --pp.
                      vveerrbboossee Same as --vv.
                      vvii      Use  a  vi-style command line editing interface.
                              This also affects the editing interface used for
                              rreeaadd --ee.
                      xxttrraaccee  Same as --xx.
                      If --oo is supplied with no _o_p_t_i_o_n_-_n_a_m_e, the values of the
                      current options are printed.  If ++oo is supplied with  no
                      _o_p_t_i_o_n_-_n_a_m_e,  a  series  of sseett commands to recreate the
                      current option settings is  displayed  on  the  standard
                      output.
              --pp      Turn  on  _p_r_i_v_i_l_e_g_e_d  mode.   In this mode, the $$EENNVV and
                      $$BBAASSHH__EENNVV files are not processed, shell  functions  are
                      not  inherited  from the environment, and the SSHHEELLLLOOPPTTSS,
                      BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they  ap-
                      pear  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 --pp option is not sup-
                      plied, these actions are taken and the effective user id
                      is  set  to  the real user id.  If the --pp 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.
              --tt      Exit after reading and executing one command.
              --uu      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.
              --vv      Print shell input lines as they are read.
              --xx      After  expanding  each _s_i_m_p_l_e _c_o_m_m_a_n_d, ffoorr command, ccaassee
                      command, sseelleecctt command, or arithmetic ffoorr command, dis-
                      play  the expanded value of PPSS44, followed by the command
                      and its expanded arguments or associated word list.
              --BB      The shell performs brace expansion (see BBrraaccee  EExxppaannssiioonn
                      above).  This is on by default.
              --CC      If  set,  bbaasshh  does not overwrite an existing file with
                      the >>, >>&&, and <<>> redirection operators.   This  may  be
                      overridden when creating output files by using the redi-
                      rection operator >>|| instead of >>.
              --EE      If set, any trap on EERRRR is inherited by shell functions,
                      command  substitutions,  and commands executed in a sub-
                      shell environment.  The EERRRR trap is normally not  inher-
                      ited in such cases.
              --HH      Enable !!  style history substitution.  This option is on
                      by default when the shell is interactive.
              --PP      If set, the shell does not resolve symbolic  links  when
                      executing  commands  such  as ccdd that change the current
                      working  directory.   It  uses  the  physical  directory
                      structure instead.  By default, bbaasshh follows the logical
                      chain of  directories  when  performing  commands  which
                      change the current directory.
              --TT      If  set,  any traps on DDEEBBUUGG and RREETTUURRNN are inherited by
                      shell functions, command substitutions, and commands ex-
                      ecuted  in a subshell environment.  The DDEEBBUUGG and RREETTUURRNN
                      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 _a_r_gs, even if  some  of  them  begin
                      with a --.
              --       Signal  the  end of options, cause all remaining _a_r_gs to
                      be assigned to the positional parameters.  The --xx and --vv
                      options are turned off.  If there are no _a_r_gs, the posi-
                      tional parameters remain unchanged.

              The options are off by default unless otherwise noted.  Using  +
              rather  than  -  causes these options to be turned off.  The op-
              tions can also be specified as arguments to an invocation of the
              shell.   The current set of options may be found in $$--.  The re-
              turn status is always true unless an invalid option  is  encoun-
              tered.

       sshhiifftt [_n]
              The  positional  parameters  from _n+1 ... are renamed to $$11 ........
              Parameters represented by the numbers $$## down to $$##-_n+1 are  un-
              set.   _n must be a non-negative number less than or equal to $$##.
              If _n is 0, no parameters are changed.  If _n is not given, it  is
              assumed to be 1.  If _n is greater than $$##, the positional param-
              eters are not changed.  The return status is greater  than  zero
              if _n is greater than $$## or less than zero; otherwise 0.

       sshhoopptt [--ppqqssuu] [--oo] [_o_p_t_n_a_m_e ...]
              Toggle  the values of settings controlling optional shell behav-
              ior.  The settings can be either those listed below, or, if  the
              --oo option is used, those available with the --oo option to the sseett
              builtin command.  With no options, or with the --pp option, a list
              of  all  settable  options  is  displayed, with an indication of
              whether or not each is set; if _o_p_t_n_a_m_e_s are supplied, the output
              is  restricted to those options.  The --pp option causes output to
              be displayed in a form that may be reused as input.   Other  op-
              tions have the following meanings:
              --ss     Enable (set) each _o_p_t_n_a_m_e.
              --uu     Disable (unset) each _o_p_t_n_a_m_e.
              --qq     Suppresses  normal output (quiet mode); the return status
                     indicates whether the _o_p_t_n_a_m_e is set or unset.  If multi-
                     ple  _o_p_t_n_a_m_e arguments are given with --qq, the return sta-
                     tus is zero if all _o_p_t_n_a_m_e_s are enabled; non-zero  other-
                     wise.
              --oo     Restricts  the  values of _o_p_t_n_a_m_e to be those defined for
                     the --oo option to the sseett builtin.

              If either --ss or --uu is used  with  no  _o_p_t_n_a_m_e  arguments,  sshhoopptt
              shows  only  those options which are set or unset, respectively.
              Unless otherwise noted, the sshhoopptt options are  disabled  (unset)
              by default.

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

              The list of sshhoopptt options is:

              aassssoocc__eexxppaanndd__oonnccee
                      If set, the shell suppresses multiple evaluation of  as-
                      sociative  array subscripts during arithmetic expression
                      evaluation, while executing builtins  that  can  perform
                      variable  assignments, and while executing builtins that
                      perform array dereferencing.
              aauuttooccdd  If set, a command name that is the name of  a  directory
                      is  executed  as  if it were the argument to the ccdd com-
                      mand.  This option is only used by interactive shells.
              ccddaabbllee__vvaarrss
                      If set, an argument to the ccdd builtin  command  that  is
                      not  a directory is assumed to be the name of a variable
                      whose value is the directory to change to.
              ccddssppeellll If set, minor errors in the spelling of a directory com-
                      ponent  in  a  ccdd command will be corrected.  The errors
                      checked for are transposed characters, a missing charac-
                      ter,  and  one  character  too many.  If a correction is
                      found, the corrected filename is printed, and  the  com-
                      mand  proceeds.  This option is only used by interactive
                      shells.
              cchheecckkhhaasshh
                      If set, bbaasshh checks that a command found in the hash ta-
                      ble  exists  before  trying  to execute it.  If a hashed
                      command no longer exists, a normal path search  is  per-
                      formed.
              cchheecckkjjoobbss
                      If set, bbaasshh 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 JJOOBB CCOONNTTRROOLL above).  The shell always postpones ex-
                      iting if any jobs are stopped.
              cchheecckkwwiinnssiizzee
                      If set, bbaasshh checks the window size after each  external
                      (non-builtin)  command  and,  if  necessary, updates the
                      values of LLIINNEESS and CCOOLLUUMMNNSS.  This option is enabled  by
                      default.
              ccmmddhhiisstt If  set,  bbaasshh attempts to save all lines of a multiple-
                      line command in the same  history  entry.   This  allows
                      easy  re-editing of multi-line commands.  This option is
                      enabled by default, but only has an  effect  if  command
                      history is enabled, as described above under HHIISSTTOORRYY.
              ccoommppaatt3311
              ccoommppaatt3322
              ccoommppaatt4400
              ccoommppaatt4411
              ccoommppaatt4422
              ccoommppaatt4433
              ccoommppaatt4444
                      These  control aspects of the shell's compatibility mode
                      (see SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below).

              ccoommpplleettee__ffuullllqquuoottee
                      If set, bbaasshh quotes all shell  metacharacters  in  file-
                      names  and  directory  names when performing completion.
                      If not set, bbaasshh 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  ex-
                      pand  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.

              ddiirreexxppaanndd
                      If set, bbaasshh 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,  bbaasshh attempts to preserve what the
                      user typed.

              ddiirrssppeellll
                      If set, bbaasshh attempts spelling correction  on  directory
                      names  during word completion if the directory name ini-
                      tially supplied does not exist.

              ddoottgglloobb If set, bbaasshh includes filenames beginning with a `.'  in
                      the  results of pathname expansion.  The filenames ````..''''
                      and ````....''''  must always be matched explicitly,  even  if
                      ddoottgglloobb is set.

              eexxeeccffaaiill
                      If set, a non-interactive shell will not exit if it can-
                      not execute the file specified as  an  argument  to  the
                      eexxeecc  builtin  command.   An  interactive shell does not
                      exit if eexxeecc fails.

              eexxppaanndd__aalliiaasseess
                      If set, aliases are expanded as  described  above  under
                      AALLIIAASSEESS.  This option is enabled by default for interac-
                      tive shells.

              eexxttddeebbuugg
                      If set at shell invocation, or in a shell startup  file,
                      arrange to execute the debugger profile before the shell
                      starts, identical to the ----ddeebbuuggggeerr option.  If set  af-
                      ter  invocation,  behavior intended for use by debuggers
                      is enabled:

                      11..     The --FF option to the ddeeccllaarree builtin displays the
                             source file name and line number corresponding to
                             each function name supplied as an argument.

                      22..     If the command run by the DDEEBBUUGG  trap  returns  a
                             non-zero  value,  the next command is skipped and
                             not executed.

                      33..     If the command run by the DDEEBBUUGG  trap  returns  a
                             value  of 2, and the shell is executing in a sub-
                             routine (a shell function or a shell script  exe-
                             cuted  by  the  ..  or ssoouurrccee builtins), the shell
                             simulates a call to rreettuurrnn.

                      44..     BBAASSHH__AARRGGCC and BBAASSHH__AARRGGVV are updated as  described
                             in their descriptions above.

                      55..     Function  tracing  is  enabled: command substitu-
                             tion, shell functions, and subshells invoked with
                             (( _c_o_m_m_a_n_d )) inherit the DDEEBBUUGG and RREETTUURRNN traps.

                      66..     Error  tracing  is enabled: command substitution,
                             shell functions, and  subshells  invoked  with  ((
                             _c_o_m_m_a_n_d )) inherit the EERRRR trap.

              eexxttgglloobb If set, the extended pattern matching features described
                      above under PPaatthhnnaammee EExxppaannssiioonn are enabled.

              eexxttqquuoottee
                      If set, $$'_s_t_r_i_n_g' and  $$"_s_t_r_i_n_g"  quoting  is  performed
                      within   $${{_p_a_r_a_m_e_t_e_r}}   expansions  enclosed  in  double
                      quotes.  This option is enabled by default.

              ffaaiillgglloobb
                      If set, patterns which fail to  match  filenames  during
                      pathname expansion result in an expansion error.

              ffoorrccee__ffiiggnnoorree
                      If  set,  the  suffixes  specified  by the FFIIGGNNOORREE shell
                      variable cause words to be ignored when performing  word
                      completion even if the ignored words are the only possi-
                      ble completions.  See SSHHEELLLL VVAARRIIAABBLLEESS above  for  a  de-
                      scription  of  FFIIGGNNOORREE.   This  option is enabled by de-
                      fault.

              gglloobbaasscciiiirraannggeess
                      If set,  range  expressions  used  in  pattern  matching
                      bracket  expressions (see PPaatttteerrnn MMaattcchhiinngg above) behave
                      as if in the traditional C locale when  performing  com-
                      parisons.   That  is, the current locale's collating se-
                      quence is not taken into account, so bb will not  collate
                      between  AA  and  BB,  and upper-case and lower-case ASCII
                      characters will collate together.

              gglloobbssttaarr
                      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.

              ggnnuu__eerrrrffmmtt
                      If set, shell error messages are written in the standard
                      GNU error message format.

              hhiissttaappppeenndd
                      If set, the history list is appended to the  file  named
                      by the value of the HHIISSTTFFIILLEE variable when the shell ex-
                      its, rather than overwriting the file.

              hhiissttrreeeeddiitt
                      If set, and rreeaaddlliinnee is being used, a user is given  the
                      opportunity to re-edit a failed history substitution.

              hhiissttvveerriiffyy
                      If  set, and rreeaaddlliinnee is being used, the results of his-
                      tory substitution are  not  immediately  passed  to  the
                      shell  parser.   Instead,  the  resulting line is loaded
                      into the rreeaaddlliinnee editing buffer, allowing further modi-
                      fication.

              hhoossttccoommpplleettee
                      If set, and rreeaaddlliinnee is being used, bbaasshh will attempt to
                      perform hostname completion when a word containing  a  @@
                      is   being  completed  (see  CCoommpplleettiinngg  under  RREEAADDLLIINNEE
                      above).  This is enabled by default.

              hhuuppoonneexxiitt
                      If set, bbaasshh will send SSIIGGHHUUPP to all jobs when an inter-
                      active login shell exits.

              iinnhheerriitt__eerrrreexxiitt
                      If  set,  command substitution inherits the value of the
                      eerrrreexxiitt option, instead of unsetting it in the  subshell
                      environment.   This option is enabled when _p_o_s_i_x _m_o_d_e is
                      enabled.

              iinntteerraaccttiivvee__ccoommmmeennttss
                      If set, allow a word beginning with ## to cause that word
                      and  all remaining characters on that line to be ignored
                      in an interactive shell (see CCOOMMMMEENNTTSS above).  This  op-
                      tion is enabled by default.

              llaassttppiippee
                      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.

              lliitthhiisstt If  set,  and  the ccmmddhhiisstt option is enabled, multi-line
                      commands are saved to the history with embedded newlines
                      rather than using semicolon separators where possible.

              llooccaallvvaarr__iinnhheerriitt
                      If set, local variables inherit the value and attributes
                      of a variable of the same name that exists at a previous
                      scope before any new value is assigned.  The nameref at-
                      tribute is not inherited.

              llooccaallvvaarr__uunnsseett
                      If set, calling uunnsseett on  local  variables  in  previous
                      function  scopes  marks  them so subsequent lookups find
                      them unset until that function returns. This is  identi-
                      cal  to the behavior of unsetting local variables at the
                      current function scope.

              llooggiinn__sshheellll
                      The shell sets this option if it is started as  a  login
                      shell  (see  IINNVVOOCCAATTIIOONN  above).   The  value may not be
                      changed.

              mmaaiillwwaarrnn
                      If set, and a file that bbaasshh is checking  for  mail  has
                      been  accessed  since  the last time it was checked, the
                      message ``The mail in _m_a_i_l_f_i_l_e has been read''  is  dis-
                      played.

              nnoo__eemmppttyy__ccmmdd__ccoommpplleettiioonn
                      If  set,  and  rreeaaddlliinnee is being used, bbaasshh will not at-
                      tempt to search the PPAATTHH for possible  completions  when
                      completion is attempted on an empty line.

              nnooccaasseegglloobb
                      If  set,  bbaasshh  matches  filenames in a case-insensitive
                      fashion when performing pathname expansion (see PPaatthhnnaammee
                      EExxppaannssiioonn above).

              nnooccaasseemmaattcchh
                      If  set,  bbaasshh  matches  patterns  in a case-insensitive
                      fashion when performing matching while executing ccaassee or
                      [[[[ conditional commands, when performing pattern substi-
                      tution word expansions, or when filtering possible  com-
                      pletions as part of programmable completion.

              nnuullllgglloobb
                      If  set,  bbaasshh allows patterns which match no files (see
                      PPaatthhnnaammee EExxppaannssiioonn above) to expand to  a  null  string,
                      rather than themselves.

              pprrooggccoommpp
                      If set, the programmable completion facilities (see PPrroo--
                      ggrraammmmaabbllee CCoommpplleettiioonn above) are enabled.  This option is
                      enabled by default.

              pprrooggccoommpp__aalliiaass
                      If  set,  and  programmable  completion is enabled, bbaasshh
                      treats a command name that doesn't have any  completions
                      as  a possible alias and attempts alias expansion. If it
                      has an alias, bbaasshh attempts programmable completion  us-
                      ing the command word resulting from the expanded alias.

              pprroommppttvvaarrss
                      If set, prompt strings undergo parameter expansion, com-
                      mand substitution, arithmetic expansion, and  quote  re-
                      moval  after  being  expanded  as described in PPRROOMMPPTTIINNGG
                      above.  This option is enabled by default.

              rreessttrriicctteedd__sshheellll
                      The shell sets this option  if  it  is  started  in  re-
                      stricted  mode  (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).  The value
                      may not be changed.  This is not reset when the  startup
                      files  are  executed, allowing the startup files to dis-
                      cover whether or not a shell is restricted.

              sshhiifftt__vveerrbboossee
                      If set, the sshhiifftt builtin prints an error  message  when
                      the shift count exceeds the number of positional parame-
                      ters.

              ssoouurrcceeppaatthh
                      If set, the ssoouurrccee (..) builtin uses the value of PPAATTHH to
                      find  the  directory  containing the file supplied as an
                      argument.  This option is enabled by default.

              xxppgg__eecchhoo
                      If set, the eecchhoo builtin  expands  backslash-escape  se-
                      quences by default.

       ssuussppeenndd [--ff]
              Suspend  the execution of this shell until it receives a SSIIGGCCOONNTT
              signal.  A login shell cannot be suspended; the --ff 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 --ff  is  not  sup-
              plied, or if job control is not enabled.

       tteesstt _e_x_p_r
       [[ _e_x_p_r ]]
              Return a status of 0 (true) or 1 (false) depending on the evalu-
              ation of the conditional expression _e_x_p_r.  Each operator and op-
              erand  must be a separate argument.  Expressions are composed of
              the primaries described in the bbaasshh  manual  page  under  CCOONNDDII--
              TTIIOONNAALL  EEXXPPRREESSSSIIOONNSS.  tteesstt 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  de-
              pends  on  the  number of arguments; see below.  Operator prece-
              dence is used when there are five or more arguments.
              !! _e_x_p_r True if _e_x_p_r is false.
              (( _e_x_p_r ))
                     Returns the value of _e_x_p_r.  This may be used to  override
                     the normal precedence of operators.
              _e_x_p_r_1 -aa _e_x_p_r_2
                     True if both _e_x_p_r_1 and _e_x_p_r_2 are true.
              _e_x_p_r_1 -oo _e_x_p_r_2
                     True if either _e_x_p_r_1 or _e_x_p_r_2 is true.

              tteesstt and [[ evaluate conditional expressions using a set of rules
              based on the number of arguments.

              0 arguments
                     The expression is false.
              1 argument
                     The expression is true if and only if the argument is not
                     null.
              2 arguments
                     If the first argument is !!, the expression is true if and
                     only if the second argument is null.  If the first  argu-
                     ment  is  one  of  the unary conditional operators listed
                     above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS,  the  expression  is
                     true if the unary test is true.  If the first argument is
                     not a valid unary conditional operator, the expression is
                     false.
              3 arguments
                     The following conditions are applied in the order listed.
                     If the second argument is one of the  binary  conditional
                     operators listed above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the
                     result of the expression is the result of the binary test
                     using  the first and third arguments as operands.  The --aa
                     and --oo 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  tteesstt  or [[, the << and >> operators sort lexico-
              graphically using ASCII ordering.

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

       ttrraapp [--llpp] [[_a_r_g] _s_i_g_s_p_e_c ...]
              The  command  _a_r_g  is to be read and executed when the shell re-
              ceives signal(s) _s_i_g_s_p_e_c.  If _a_r_g is absent (and there is a sin-
              gle  _s_i_g_s_p_e_c) or --, each specified signal is reset to its origi-
              nal disposition (the value it had upon entrance to  the  shell).
              If  _a_r_g  is the null string the signal specified by each _s_i_g_s_p_e_c
              is ignored by the shell and by the commands it invokes.  If  _a_r_g
              is  not present and --pp has been supplied, then the trap commands
              associated with each _s_i_g_s_p_e_c are displayed.  If no arguments are
              supplied  or  if  only --pp is given, ttrraapp prints the list of com-
              mands associated with each signal.  The  --ll  option  causes  the
              shell  to  print  a list of signal names and their corresponding
              numbers.  Each _s_i_g_s_p_e_c is either a signal name defined in  <_s_i_g_-
              _n_a_l_._h>,  or  a signal number.  Signal names are case insensitive
              and the SSIIGG prefix is optional.

              If a _s_i_g_s_p_e_c is EEXXIITT (0) the command _a_r_g  is  executed  on  exit
              from  the shell.  If a _s_i_g_s_p_e_c is DDEEBBUUGG, the command _a_r_g is exe-
              cuted before every _s_i_m_p_l_e _c_o_m_m_a_n_d, _f_o_r  command,  _c_a_s_e  command,
              _s_e_l_e_c_t  command,  every  arithmetic  _f_o_r command, and before the
              first command executes in a shell function  (see  SSHHEELLLL  GGRRAAMMMMAARR
              above).   Refer to the description of the eexxttddeebbuugg option to the
              sshhoopptt builtin for details of its effect on the DDEEBBUUGG trap.  If a
              _s_i_g_s_p_e_c is RREETTUURRNN, the command _a_r_g is executed each time a shell
              function or a script executed with the .. or ssoouurrccee builtins fin-
              ishes executing.

              If  a  _s_i_g_s_p_e_c  is  EERRRR,  the command _a_r_g 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 EERRRR trap is not executed  if  the
              failed command is part of the command list immediately following
              a wwhhiillee or uunnttiill keyword, part of the test in an  _i_f  statement,
              part of a 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 eerrrreexxiitt (--ee) op-
              tion.

              Signals ignored upon entry to the shell cannot be trapped or re-
              set.  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  _s_i_g_s_p_e_c  is
              invalid; otherwise ttrraapp returns true.

       ttyyppee [--aaffttppPP] _n_a_m_e [_n_a_m_e ...]
              With  no options, indicate how each _n_a_m_e would be interpreted if
              used as a command name.  If the --tt option is used, ttyyppee prints a
              string  which  is  one  of _a_l_i_a_s, _k_e_y_w_o_r_d, _f_u_n_c_t_i_o_n, _b_u_i_l_t_i_n, or
              _f_i_l_e if  _n_a_m_e  is  an  alias,  shell  reserved  word,  function,
              builtin,  or disk file, respectively.  If the _n_a_m_e is not found,
              then nothing is printed, and an exit  status  of  false  is  re-
              turned.   If the --pp option is used, ttyyppee either returns the name
              of the disk file that would be executed if _n_a_m_e  were  specified
              as  a command name, or nothing if ``type -t name'' would not re-
              turn _f_i_l_e.  The --PP option forces a PPAATTHH search  for  each  _n_a_m_e,
              even if ``type -t name'' would not return _f_i_l_e.  If a command is
              hashed, --pp and --PP print the hashed value, which is not necessar-
              ily  the  file  that appears first in PPAATTHH.  If the --aa option is
              used, ttyyppee prints all of the places that contain  an  executable
              named _n_a_m_e.  This includes aliases and functions, if and only if
              the --pp option is not also used.  The table of hashed commands is
              not  consulted  when  using  --aa.  The --ff option suppresses shell
              function lookup, as with the ccoommmmaanndd builtin.  ttyyppee returns true
              if all of the arguments are found, false if any are not found.

       uulliimmiitt [--HHSS] --aa
       uulliimmiitt [--HHSS] [--bbccddeeffiikkllmmnnppqqrrssttuuvvxxPPRRTT [_l_i_m_i_t]]
              Provides  control  over the resources available to the shell and
              to processes started by it, on systems that allow such  control.
              The --HH and --SS options specify that the hard or soft limit is set
              for the given resource.  A hard limit cannot be increased  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 --HH nor --SS is  speci-
              fied, both the soft and hard limits are set.  The value of _l_i_m_i_t
              can be a number in the unit specified for the resource or one of
              the special values hhaarrdd, ssoofftt, or uunnlliimmiitteedd, which stand for the
              current hard limit, the current soft limit, and  no  limit,  re-
              spectively.   If _l_i_m_i_t is omitted, the current value of the soft
              limit of the resource is printed, unless the --HH option is given.
              When  more  than  one  resource is specified, the limit name and
              unit, if appropriate, are printed before the value.   Other  op-
              tions are interpreted as follows:
              --aa     All current limits are reported; no limits are set
              --bb     The maximum socket buffer size
              --cc     The maximum size of core files created
              --dd     The maximum size of a process's data segment
              --ee     The maximum scheduling priority ("nice")
              --ff     The  maximum  size  of files written by the shell and its
                     children
              --ii     The maximum number of pending signals
              --kk     The maximum number of kqueues that may be allocated
              --ll     The maximum size that may be locked into memory
              --mm     The maximum resident set size (many systems do not  honor
                     this limit)
              --nn     The maximum number of open file descriptors (most systems
                     do not allow this value to be set)
              --pp     The pipe size in 512-byte blocks (this may not be set)
              --qq     The maximum number of bytes in POSIX message queues
              --rr     The maximum real-time scheduling priority
              --ss     The maximum stack size
              --tt     The maximum amount of cpu time in seconds
              --uu     The maximum number of processes  available  to  a  single
                     user
              --vv     The  maximum  amount  of  virtual memory available to the
                     shell and, on some systems, to its children
              --xx     The maximum number of file locks
              --PP     The maximum number of pseudoterminals
              --RR     The maximum time  a  real-time  process  can  run  before
                     blocking, in microseconds
              --TT     The maximum number of threads

              If  _l_i_m_i_t  is given, and the --aa option is not used, _l_i_m_i_t is the
              new value of the specified resource.  If  no  option  is  given,
              then  --ff is assumed.  Values are in 1024-byte increments, except
              for --tt, which is in seconds; --RR, which is in  microseconds;  --pp,
              which  is  in  units of 512-byte blocks; --PP, --TT, --bb, --kk, --nn, and
              --uu, which are unscaled values; and, when in posix mode,  --cc  and
              --ff,  which  are  in 512-byte increments.  The return status is 0
              unless an invalid option or argument is supplied,  or  an  error
              occurs while setting a new limit.

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

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

       uunnsseett [-ffvv] [-nn] [_n_a_m_e ...]
              For each _n_a_m_e, remove the corresponding  variable  or  function.
              If the --vv option is given, each _n_a_m_e refers to a shell variable,
              and that variable is removed.  Read-only variables  may  not  be
              unset.   If  --ff  is specified, each _n_a_m_e refers to a shell func-
              tion, and the function definition is removed.  If the --nn  option
              is  supplied, and _n_a_m_e is a variable with the _n_a_m_e_r_e_f attribute,
              _n_a_m_e will be unset rather than the variable it  references.   --nn
              has  no  effect if the --ff option is supplied.  If no options are
              supplied, each _n_a_m_e refers to a variable; if there is  no  vari-
              able  by that name, a function with that name, if any, is unset.
              Each unset variable or function is removed from the  environment
              passed   to   subsequent  commands.   If  any  of  BBAASSHH__AALLIIAASSEESS,
              BBAASSHH__AARRGGVV00,  BBAASSHH__CCMMDDSS,  BBAASSHH__CCOOMMMMAANNDD,  BBAASSHH__SSUUBBSSHHEELLLL,  BBAASSHHPPIIDD,
              CCOOMMPP__WWOORRDDBBRREEAAKKSS,  DDIIRRSSTTAACCKK,  EEPPOOCCHHRREEAALLTTIIMMEE,  EEPPOOCCHHSSEECCOONNDDSS, FFUUNNCC--
              NNAAMMEE, GGRROOUUPPSS, HHIISSTTCCMMDD, LLIINNEENNOO, RRAANNDDOOMM, SSEECCOONNDDSS, or  SSRRAANNDDOOMM  are
              unset, they lose their special properties, even if they are sub-
              sequently reset.  The exit status is true unless a _n_a_m_e is read-
              only.

       wwaaiitt [--ffnn] [--pp _v_a_r_n_a_m_e] [_i_d _._._.]
              Wait for each specified child process and return its termination
              status.  Each _i_d 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 _i_d is not given,  wwaaiitt  waits  for  all  running
              background  jobs  and the last-executed process substitution, if
              its process id is the same as $$!!, and the return status is zero.
              If  the  --nn option is supplied, wwaaiitt waits for a single job from
              the list of _i_ds or, if no _i_ds are supplied, any job, to complete
              and  returns its exit status.  If none of the supplied arguments
              is a child of the shell, or if no arguments are supplied and the
              shell  has no unwaited-for children, the exit status is 127.  If
              the --pp option is supplied, the process or job identifier of  the
              job  for  which  the  exit status is returned is assigned to the
              variable _v_a_r_n_a_m_e named by the  option  argument.   The  variable
              will  be unset initially, before any assignment.  This is useful
              only when the --nn option is supplied.  Supplying the  --ff  option,
              when  job control is enabled, forces wwaaiitt to wait for _i_d to ter-
              minate before returning its status, instead of returning when it
              changes  status.  If _i_d 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.

SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE
       Bash-4.0 introduced the concept of a `shell compatibility level', spec-
       ified as a set of options to the shopt builtin ccoommppaatt3311, ccoommppaatt3322, ccoomm--
       ppaatt4400,  ccoommppaatt4411,  and so on).  There is only one current compatibility
       level -- each option is mutually exclusive.  The compatibility level is
       intended  to allow users to select behavior from previous versions that
       is incompatible with newer versions while they migrate scripts  to  use
       current  features  and  behavior. It's intended to be a temporary solu-
       tion.

       This section does not mention behavior that is standard for a  particu-
       lar  version  (e.g., setting ccoommppaatt3322 means that quoting the rhs of the
       regexp matching operator quotes special regexp characters in the  word,
       which is default behavior in bash-3.2 and above).

       If  a  user enables, say, ccoommppaatt3322, it may affect the behavior of other
       compatibility levels up to  and  including  the  current  compatibility
       level.   The  idea  is  that each compatibility level controls behavior
       that changed in that version of bbaasshh, but that behavior may  have  been
       present  in  earlier versions.  For instance, the change to use locale-
       based comparisons with the [[[[ command came  in  bash-4.1,  and  earlier
       versions used ASCII-based comparisons, so enabling ccoommppaatt3322 will enable
       ASCII-based comparisons as well.  That granularity may  not  be  suffi-
       cient  for  all uses, and as a result users should employ compatibility
       levels carefully.  Read the documentation for a particular  feature  to
       find out the current behavior.

       Bash-4.3  introduced  a new shell variable: BBAASSHH__CCOOMMPPAATT.  The value as-
       signed to this variable (a decimal version number like 4.2, or an inte-
       ger  corresponding to the ccoommppaatt_N_N option, like 42) determines the com-
       patibility level.

       Starting with bash-4.4, Bash has begun deprecating older  compatibility
       levels.   Eventually, the options will be removed in favor of BBAASSHH__CCOOMM--
       PPAATT.

       Bash-5.0 is the final version for which there  will  be  an  individual
       shopt  option for the previous version. Users should use BBAASSHH__CCOOMMPPAATT on
       bash-5.0 and later versions.

       The following table describes the behavior changes controlled  by  each
       compatibility level setting.  The ccoommppaatt_N_N tag is used as shorthand for
       setting the compatibility level to _N_N using one of the following mecha-
       nisms.   For versions prior to bash-5.0, the compatibility level may be
       set using the corresponding ccoommppaatt_N_N shopt option.   For  bash-4.3  and
       later  versions,  the  BBAASSHH__CCOOMMPPAATT variable is preferred, and it is re-
       quired for bash-5.1 and later versions.

       ccoommppaatt3311
              +o      quoting the rhs of the [[[[ command's regexp matching oper-
                     ator (=~) has no special effect

       ccoommppaatt3322
              +o      interrupting  a  command  list such as "a ; b ; c" causes
                     the execution  of  the  next  command  in  the  list  (in
                     bash-4.0  and later versions, the shell acts as if it re-
                     ceived the interrupt, so interrupting one  command  in  a
                     list aborts the execution of the entire list)

       ccoommppaatt4400
              +o      the  <<  and >> operators to the [[[[ command do not consider
                     the current locale when comparing strings; they use ASCII
                     ordering.  Bash versions prior to bash-4.1 use ASCII col-
                     lation and _s_t_r_c_m_p(3); bash-4.1 and later use the  current
                     locale's collation sequence and _s_t_r_c_o_l_l(3).

       ccoommppaatt4411
              +o      in  _p_o_s_i_x mode, ttiimmee may be followed by options and still
                     be recognized as a reserved word (this is POSIX interpre-
                     tation 267)
              +o      in _p_o_s_i_x mode, the parser requires that an even number of
                     single quotes occur in the  _w_o_r_d  portion  of  a  double-
                     quoted  parameter expansion and treats them specially, so
                     that characters within the single quotes  are  considered
                     quoted (this is POSIX interpretation 221)

       ccoommppaatt4422
              +o      the replacement string in double-quoted pattern substitu-
                     tion does not undergo quote removal, as it does  in  ver-
                     sions after bash-4.2
              +o      in  posix mode, single quotes are considered special when
                     expanding the _w_o_r_d portion of a  double-quoted  parameter
                     expansion  and  can  be  used to quote a closing brace or
                     other special character (this is part of POSIX  interpre-
                     tation  221);  in  later  versions, single quotes are not
                     special within double-quoted word expansions

       ccoommppaatt4433
              +o      the shell does not print a warning message if an  attempt
                     is  made  to use a quoted compound assignment as an argu-
                     ment to declare (declare -a foo='(1 2)'). Later  versions
                     warn that this usage is deprecated
              +o      word  expansion  errors  are  considered non-fatal errors
                     that cause the current command to  fail,  even  in  posix
                     mode  (the  default behavior is to make them fatal errors
                     that cause the shell to exit)
              +o      when  executing  a  shell  function,   the   loop   state
                     (while/until/etc.)  is not reset, so bbrreeaakk or ccoonnttiinnuuee in
                     that function will break or continue loops in the calling
                     context.  Bash-4.4 and later reset the loop state to pre-
                     vent this

       ccoommppaatt4444
              +o      the shell sets  up  the  values  used  by  BBAASSHH__AARRGGVV  and
                     BBAASSHH__AARRGGCC  so  they  can expand to the shell's positional
                     parameters even if extended debugging mode is not enabled
              +o      a subshell inherits loops from  its  parent  context,  so
                     bbrreeaakk  or  ccoonnttiinnuuee  will  cause  the  subshell  to exit.
                     Bash-5.0 and later reset the loop state  to  prevent  the
                     exit
              +o      variable  assignments  preceding builtins like eexxppoorrtt and
                     rreeaaddoonnllyy that set attributes continue to affect variables
                     with the same name in the calling environment even if the
                     shell is not in posix mode

       ccoommppaatt5500
              +o      Bash-5.1 changed the way $$RRAANNDDOOMM is generated  to  intro-
                     duce slightly more randomness. If the shell compatibility
                     level is set to 50 or lower, it  reverts  to  the  method
                     from  bash-5.0 and previous versions, so seeding the ran-
                     dom number generator by assigning a value to RRAANNDDOOMM  will
                     produce the same sequence as in bash-5.0
              +o      If  the  command hash table is empty, bash versions prior
                     to bash-5.1 printed an informational message to that  ef-
                     fect,  even  when  producing output that can be reused as
                     input. Bash-5.1 suppresses that message when the  --ll  op-
                     tion is supplied.

SSEEEE AALLSSOO
       bash(1), sh(1)



GNU Bash 5.0                      2004 Apr 20                 BASH_BUILTINS(1)