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NAZWA

       bash-builtins - wbudowane polecenia basha, patrz bash(1)

SKŁADNIA

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

WBUDOWANE POLECENIA BASH

       Unless  otherwise noted, each builtin command documented in this section as accepting options preceded by
       - accepts -- to signify the end of the options.  The :, true, false, and test/[ builtins  do  not  accept
       options  and  do  not  treat  --  specially.   The  exit, logout, return, break, continue, let, and shift
       builtins accept and process arguments beginning with - without requiring --.  Other builtins that  accept
       arguments  but  are  not  specified  as accepting options interpret arguments beginning with - as invalid
       options and require -- to prevent this interpretation.
       : [arguments]
              No effect; the command does nothing  beyond  expanding  arguments  and  performing  any  specified
              redirections.  The return status is zero.

        .  filename [arguments]
       source filename [arguments]
              Read  and  execute  commands  from  filename  in the current shell environment and return the exit
              status of the last command executed  from  filename.   If  filename  does  not  contain  a  slash,
              filenames  in  PATH  are used to find the directory containing filename.  The file searched for in
              PATH need not be executable.  When bash is not in posix mode, the current directory is searched if
              no  file  is  found in PATH.  If the sourcepath option to the shopt builtin command is turned off,
              the PATH is not searched.  If any arguments are supplied, they become  the  positional  parameters
              when  filename  is executed.  Otherwise the positional parameters are unchanged.  If the -T option
              is enabled, source inherits any trap on DEBUG; if it is not, any DEBUG trap string  is  saved  and
              restored  around the call to source, and source unsets the DEBUG trap while it executes.  If -T is
              not set, and the sourced file changes the DEBUG trap,  the  new  value  is  retained  when  source
              completes.   The return status is the status of the last command exited within the script (0 if no
              commands are executed), and false if filename is not found or cannot be read.

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

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

       bind [-m keymap] [-lpsvPSVX]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] -x keyseq:shell-command
       bind [-m keymap] keyseq:function-name
       bind [-m keymap] keyseq:readline-command
              Display current readline key and function bindings, bind a key sequence to a readline function  or
              macro,  or  set  a readline variable.  Each non-option argument is a command as it would appear in
              .inputrc, but each binding or command must be passed as a separate  argument;  e.g.,  '"\C-x\C-r":
              re-read-init-file'.  Options, if supplied, have the following meanings:
              -m keymap
                     Use  keymap  as  the  keymap  to be affected by the subsequent bindings.  Acceptable keymap
                     names are emacs, emacs-standard,  emacs-meta,  emacs-ctlx,  vi,  vi-move,  vi-command,  and
                     vi-insert.  vi is equivalent to vi-command (vi-move is also a synonym); emacs is equivalent
                     to emacs-standard.
              -l     List the names of all readline functions.
              -p     Display readline function names and bindings in such a way that they can be re-read.
              -P     List current readline function names and bindings.
              -s     Display readline key sequences bound to macros and the strings they output in  such  a  way
                     that they can be re-read.
              -S     Display readline key sequences bound to macros and the strings they output.
              -v     Display readline variable names and values in such a way that they can be re-read.
              -V     List current readline variable names and values.
              -f filename
                     Read key bindings from filename.
              -q function
                     Query about which keys invoke the named function.
              -u function
                     Unbind all keys bound to the named function.
              -r keyseq
                     Remove any current binding for keyseq.
              -x keyseq:shell-command
                     Cause  shell-command  to  be  executed  whenever  keyseq is entered.  When shell-command is
                     executed, the shell sets the READLINE_LINE variable to the contents of  the  readline  line
                     buffer  and the READLINE_POINT variable to the current location of the insertion point.  If
                     the executed command changes the value of READLINE_LINE or READLINE_POINT, those new values
                     will be reflected in the editing state.
              -X     List all key sequences bound to shell commands and the associated commands in a format that
                     can be reused as input.

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

       break [n]
              Exit from within a for, while, until, or select loop.  If n is specified, break n levels.  n  must
              be  ≥ 1.  If n is greater than the number of enclosing loops, all enclosing loops are exited.  The
              return value is 0 unless n is not greater than or equal to 1.

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

       caller [expr]
              Returns  the context of any active subroutine call (a shell function or a script executed with the
              . or source builtins).  Without expr, caller displays the line number and source filename  of  the
              current  subroutine call.  If a non-negative integer is supplied as expr, caller displays the line
              number, subroutine name, and source file corresponding to that position in the  current  execution
              call stack.  This extra information may be used, for example, to print a stack trace.  The current
              frame is frame 0.  The return value is 0 unless the shell is not executing a  subroutine  call  or
              expr does not correspond to a valid position in the call stack.

       cd [-L|[-P [-e]] [-@]] [dir]
              Change the current directory to dir.  if dir is not supplied, the value of the HOME shell variable
              is the default.  Any additional arguments following dir are ignored.  The variable CDPATH  defines
              the  search  path  for the directory containing dir: each directory name in CDPATH is searched for
              dir.  Alternative directory names in CDPATH are separated by a colon (:).  A null  directory  name
              in CDPATH is the same as the current directory, i.e., ``.''.  If dir begins with a slash (/), then
              CDPATH is not used.  The -P option causes cd to use the physical directory structure by  resolving
              symbolic  links while traversing dir and before processing instances of .. in dir (see also the -P
              option to the set builtin command); the  -L  option  forces  symbolic  links  to  be  followed  by
              resolving the link after processing instances of .. in dir.  If .. appears in dir, it is processed
              by removing the immediately previous pathname component from dir, back to a slash or the beginning
              of  dir.   If  the  -e  option  is  supplied  with -P, and the current working directory cannot be
              successfully determined after a successful  directory  change,  cd  will  return  an  unsuccessful
              status.   On  systems  that  support it, the -@ option presents the extended attributes associated
              with a file as a directory.  An argument of - is converted to $OLDPWD before the directory  change
              is  attempted.   If a non-empty directory name from CDPATH is used, or if - is the first argument,
              and the directory change is successful, the absolute pathname of  the  new  working  directory  is
              written  to  the  standard  output.   The  return  value is true if the directory was successfully
              changed; false otherwise.

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

       compgen [option] [word]
              Generate possible completion matches for word according to the options, which may  be  any  option
              accepted  by  the  complete  builtin with the exception of -p and -r, and write the matches to the
              standard output.  When using the -F or  -C  options,  the  various  shell  variables  set  by  the
              programmable completion facilities, while available, will not have useful values.

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

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

       complete [-abcdefgjksuv] [-o comp-option] [-DEI] [-A action] [-G globpat] [-W wordlist] [-F function] [-C
       command]
              [-X filterpat] [-P prefix] [-S suffix] name [name ...]
       complete -pr [-DEI] [name ...]
              Specify how arguments to each name should be completed.  If the -p option is supplied,  or  if  no
              options  are supplied, existing completion specifications are printed in a way that allows them to
              be reused as input.  The -r option removes a completion specification for each  name,  or,  if  no
              names  are  supplied,  all completion specifications.  The -D option indicates that other supplied
              options and actions should apply to  the  ``default''  command  completion;  that  is,  completion
              attempted  on  a  command  for  which  no  completion  has previously been defined.  The -E option
              indicates that other supplied options and actions should apply to  ``empty''  command  completion;
              that  is,  completion  attempted  on  a  blank  line.  The -I option indicates that other supplied
              options and actions should apply to completion on the inital 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 -D option takes precedence over -E, and both take  precedence  over  -I.
              If any of -D, -E, or -I are supplied, any other name 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 Programmable Completion.

              Other  options,  if  specified,  have the following meanings.  The arguments to the -G, -W, and -X
              options (and, if necessary, the -P and -S options) should be quoted to protect them from expansion
              before the complete builtin is invoked.
              -o comp-option
                      The  comp-option  controls  several  aspects  of the compspec's behavior beyond the simple
                      generation of completions.  comp-option may be one of:
                      bashdefault
                              Perform the rest of the default bash completions  if  the  compspec  generates  no
                              matches.
                      default Use readline's default filename completion if the compspec generates no matches.
                      dirnames
                              Perform directory name completion if the compspec generates no matches.
                      filenames
                              Tell  readline  that  the  compspec  generates  filenames,  so  it can perform any
                              filename-specific processing (like adding a  slash  to  directory  names,  quoting
                              special  characters,  or  suppressing  trailing spaces).  Intended to be used with
                              shell functions.
                      noquote Tell readline not to quote the completed words  if  they  are  filenames  (quoting
                              filenames is the default).
                      nosort  Tell readline not to sort the list of possible completions alphabetically.
                      nospace Tell readline not to append a space (the default) to words completed at the end of
                              the line.
                      plusdirs
                              After any matches defined by the compspec are generated, directory name completion
                              is attempted and any matches are added to the results of the other actions.
              -A action
                      The action may be one of the following to generate a list of possible completions:
                      alias   Alias names.  May also be specified as -a.
                      arrayvar
                              Array variable names.
                      binding Readline key binding names.
                      builtin Names of shell builtin commands.  May also be specified as -b.
                      command Command names.  May also be specified as -c.
                      directory
                              Directory names.  May also be specified as -d.
                      disabled
                              Names of disabled shell builtins.
                      enabled Names of enabled shell builtins.
                      export  Names of exported shell variables.  May also be specified as -e.
                      file    File names.  May also be specified as -f.
                      function
                              Names of shell functions.
                      group   Group names.  May also be specified as -g.
                      helptopic
                              Help topics as accepted by the help builtin.
                      hostname
                              Hostnames, as taken from the file specified by the HOSTFILE shell variable.
                      job     Job names, if job control is active.  May also be specified as -j.
                      keyword Shell reserved words.  May also be specified as -k.
                      running Names of running jobs, if job control is active.
                      service Service names.  May also be specified as -s.
                      setopt  Valid arguments for the -o option to the set builtin.
                      shopt   Shell option names as accepted by the shopt builtin.
                      signal  Signal names.
                      stopped Names of stopped jobs, if job control is active.
                      user    User names.  May also be specified as -u.
                      variable
                              Names of all shell variables.  May also be specified as -v.
              -C command
                      command  is  executed  in  a  subshell environment, and its output is used as the possible
                      completions.
              -F function
                      The shell function function is executed  in  the  current  shell  environment.   When  the
                      function  is  executed, the first argument ($1) is the name of the command whose arguments
                      are being completed, the second argument ($2) is the word being completed, and  the  third
                      argument  ($3) is the word preceding the word being completed on the current command line.
                      When it finishes, the possible completions are retrieved from the value of  the  COMPREPLY
                      array variable.
              -G globpat
                      The pathname expansion pattern globpat is expanded to generate the possible completions.
              -P prefix
                      prefix  is added at the beginning of each possible completion after all other options have
                      been applied.
              -S suffix
                      suffix is appended to each possible completion after all other options have been applied.
              -W wordlist
                      The wordlist is split using the characters in the IFS special variable as delimiters,  and
                      each  resultant  word  is expanded.  Shell quoting is honored within wordlist, in order to
                      provide a mechanism for the words to contain shell metacharacters  or  characters  in  the
                      value  of IFS.  The possible completions are the members of the resultant list which match
                      the word being completed.
              -X filterpat
                      filterpat is a pattern as used for pathname expansion.  It  is  applied  to  the  list  of
                      possible completions generated by the preceding options and arguments, and each completion
                      matching filterpat is removed from the  list.   A  leading  !  in  filterpat  negates  the
                      pattern; in this case, any completion not matching filterpat is removed.

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

       compopt [-o option] [-DEI] [+o option] [name]
              Modify  completion  options for each name according to the options, or for the currently-executing
              completion if no names are supplied.  If no options are given, display the completion options  for
              each  name  or  the  current  completion.   The  possible values of option are those valid for the
              complete builtin described above.  The -D option indicates  that  other  supplied  options  should
              apply  to the ``default'' command completion; that is, completion attempted on a command for which
              no completion has previously been defined.  The -E option indicates that  other  supplied  options
              should  apply to ``empty'' command completion; that is, completion attempted on a blank line.  The
              -I option indicates that other supplied options should apply to  completion  on  the  inital  non-
              assignment word on the line, or after a command 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 name for which no completion specification exists, or an output error occurs.

       continue [n]
              Resume  the next iteration of the enclosing for, while, until, or select loop.  If n is specified,
              resume at the nth enclosing loop.  n must be ≥ 1.  If n is greater than the  number  of  enclosing
              loops,  the last enclosing loop (the ``top-level'' loop) is resumed.  The return value is 0 unless
              n is not greater than or equal to 1.

       declare [-aAfFgilnrtux] [-p] [name[=value] ...]
       typeset [-aAfFgilnrtux] [-p] [name[=value] ...]
              Declare variables and/or give them attributes.  If no names are given then display the  values  of
              variables.   The  -p  option will display the attributes and values of each name.  When -p is used
              with name arguments, additional options, other than -f and -F, are ignored.  When -p  is  supplied
              without  name  arguments,  it  will  display the attributes and values of all variables having the
              attributes specified by the additional options.  If no other options are supplied with -p, declare
              will  display  the  attributes and values of all shell variables.  The -f option will restrict the
              display to shell functions.  The -F option inhibits the display of function definitions; only  the
              function  name  and  attributes are printed.  If the extdebug shell option is enabled using shopt,
              the source file name and line number where each name is defined are displayed  as  well.   The  -F
              option  implies -f.  The -g option forces variables to be created or modified at the global scope,
              even when declare is executed in a shell function.   It  is  ignored  in  all  other  cases.   The
              following  options  can be used to restrict output to variables with the specified attribute or to
              give variables attributes:
              -a     Each name is an indexed array variable (see Arrays above).
              -A     Each name is an associative array variable (see Arrays above).
              -f     Use function names only.
              -i     The variable is treated as an integer; arithmetic  evaluation  (see  ARITHMETIC  EVALUATION
                     above) is performed when the variable is assigned a value.
              -l     When  the  variable  is assigned a value, all upper-case characters are converted to lower-
                     case.  The upper-case attribute is disabled.
              -n     Give each name the nameref attribute, making it a name reference to another variable.  That
                     other variable is defined by the value of name.  All references, assignments, and attribute
                     modifications to name, except  those  using  or  changing  the  -n  attribute  itself,  are
                     performed  on  the  variable  referenced  by name's value.  The nameref attribute cannot be
                     applied to array variables.
              -r     Make names readonly.  These names cannot then be assigned values by  subsequent  assignment
                     statements or unset.
              -t     Give  each  name  the trace attribute.  Traced functions inherit the DEBUG and RETURN traps
                     from the calling shell.  The trace attribute has no special meaning for variables.
              -u     When the variable is assigned a value, all lower-case characters are  converted  to  upper-
                     case.  The lower-case attribute is disabled.
              -x     Mark names for export to subsequent commands via the environment.

              Using  `+'  instead of `-' turns off the attribute instead, with the exceptions that +a and +A may
              not be used to destroy array variables and +r will not remove the readonly attribute.   When  used
              in  a function, declare and typeset make each name local, as with the local command, unless the -g
              option is supplied.  If a variable name is followed by =value, the value of the variable is set to
              value.   When  using  -a  or  -A  and  the  compound  assignment syntax to create array variables,
              additional attributes do not take effect until subsequent assignments.   The  return  value  is  0
              unless  an  invalid  option  is  encountered,  an  attempt is made to define a function using ``-f
              foo=bar'', an attempt is made to assign a value to a readonly variable,  an  attempt  is  made  to
              assign  a  value  to  an  array  variable without using the compound assignment syntax (see Arrays
              above), one of the names is not a valid shell variable name,  an  attempt  is  made  to  turn  off
              readonly  status for a readonly variable, an attempt is made to turn off array status for an array
              variable, or an attempt is made to display a non-existent function with -f.

       dirs [-clpv] [+n] [-n]
              Without options, displays the list of currently remembered directories.  The default display is on
              a  single  line  with directory names separated by spaces.  Directories are added to the list with
              the pushd command; the popd command removes entries from  the  list.   The  current  directory  is
              always the first directory in the stack.
              -c     Clears the directory stack by deleting all of the entries.
              -l     Produces  a listing using full pathnames; the default listing format uses a tilde to denote
                     the home directory.
              -p     Print the directory stack with one entry per line.
              -v     Print the directory stack with one entry per line, prefixing each entry with its  index  in
                     the stack.
              +n     Displays  the  nth  entry  counting  from  the  left of the list shown by dirs when invoked
                     without options, starting with zero.
              -n     Displays the nth entry counting from the right of the  list  shown  by  dirs  when  invoked
                     without options, starting with zero.

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

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

       echo [-neE] [arg ...]
              Output  the  args,  separated  by  spaces, followed by a newline.  The return status is 0 unless a
              write error occurs.  If -n is specified, the trailing newline is suppressed.  If the -e option  is
              given,  interpretation  of  the  following backslash-escaped characters is enabled.  The -E option
              disables the interpretation of these escape characters, even on systems where they are interpreted
              by  default.   The  xpg_echo shell option may be used to dynamically determine whether or not echo
              expands these escape characters by default.  echo does  not  interpret  --  to  mean  the  end  of
              options.  echo interprets the following escape sequences:
              \a     alert (bell)
              \b     backspace
              \c     suppress further output
              \e
              \E     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\     backslash
              \0nnn  the eight-bit character whose value is the octal value nnn (zero to three octal digits)
              \xHH   the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)
              \uHHHH the  Unicode  (ISO/IEC  10646)  character whose value is the hexadecimal value HHHH (one to
                     four hex digits)
              \UHHHHHHHH
                     the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHHHHHH (one to
                     eight hex digits)

       enable [-a] [-dnps] [-f filename] [name ...]
              Enable  and  disable  builtin shell commands.  Disabling a builtin allows a disk command which has
              the same name as a shell builtin to be executed without specifying a full  pathname,  even  though
              the  shell  normally  searches  for  builtins  before  disk commands.  If -n is used, each name is
              disabled; otherwise, names are enabled.  For example, to use the test binary found  via  the  PATH
              instead of the shell builtin version, run ``enable -n test''.  The -f option means to load the new
              builtin command name from shared object filename, on systems that support dynamic loading.  The -d
              option will delete a builtin previously loaded with -f.  If no name arguments are given, or if the
              -p option is supplied, a list of shell builtins is printed.  With no other option  arguments,  the
              list  consists  of  all  enabled  shell  builtins.   If -n is supplied, only disabled builtins are
              printed.  If -a is supplied, the list printed includes all builtins, with an indication of whether
              or  not  each  is  enabled.   If  -s  is  supplied,  the output is restricted to the POSIX special
              builtins.  The return value is 0 unless a name is not a shell builtin or there is an error loading
              a new builtin from a shared object.

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

       exec [-cl] [-a name] [command [arguments]]
              If  command is specified, it replaces the shell.  No new process is created.  The arguments become
              the arguments to command.  If the -l option is supplied, the shell places a dash at the  beginning
              of  the  zeroth  argument  passed  to  command.  This is what login(1) does.  The -c option causes
              command to be executed with an empty environment.  If -a is supplied, the shell passes name as the
              zeroth  argument  to  the executed command.  If command cannot be executed for some reason, a non-
              interactive shell exits, unless the execfail shell option is enabled.  In that  case,  it  returns
              failure.   An  interactive shell returns failure if the file cannot be executed.  A subshell exits
              unconditionally if exec fails.  If command is not specified, any redirections take effect  in  the
              current  shell, and the return status is 0.  If there is a redirection error, the return status is
              1.

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

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

       fc [-e ename] [-lnr] [first] [last]
       fc -s [pat=rep] [cmd]
              The  first  form selects a range of commands from first to last from the history list and displays
              or edits and re-executes them.  First and last may be specified as a string (to  locate  the  last
              command  beginning  with  that  string)  or  as  a number (an index into the history list, where a
              negative number is used as an offset from the current command number).  If last is not  specified,
              it  is  set to the current command for listing (so that ``fc -l -10'' prints the last 10 commands)
              and to first otherwise.  If first is not specified, it is set to the previous command for  editing
              and -16 for listing.

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

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

              If  the first form is used, the return value is 0 unless an invalid option is encountered or first
              or last specify history lines out of range.  If the -e option is supplied, the return value is the
              value  of  the  last  command  executed  or  failure if an error occurs with the temporary file of
              commands.  If the second form is used, the return status  is  that  of  the  command  re-executed,
              unless cmd does not specify a valid history line, in which case fc returns failure.

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

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

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

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

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

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

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

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

       hash [-lr] [-p filename] [-dt] [name]
              Each time hash is invoked, the full pathname of the command name is determined  by  searching  the
              directories  in $PATH and remembered.  Any previously-remembered pathname is discarded.  If the -p
              option is supplied, no path search is performed, and filename is used as the full filename of  the
              command.  The -r option causes the shell to forget all remembered locations.  The -d option causes
              the shell to forget the remembered location of each name.  If the -t option is supplied, the  full
              pathname  to which each name corresponds is printed.  If multiple name arguments are supplied with
              -t, the name is printed before the hashed full pathname.   The  -l  option  causes  output  to  be
              displayed  in  a  format that may be reused as input.  If no arguments are given, or if only -l is
              supplied, information about remembered commands is printed.  The return status is  true  unless  a
              name is not found or an invalid option is supplied.

       help [-dms] [pattern]
              Display  helpful information about builtin commands.  If pattern is specified, help gives detailed
              help on all commands matching pattern; otherwise help for  all  the  builtins  and  shell  control
              structures is printed.
              -d     Display a short description of each pattern
              -m     Display the description of each pattern in a manpage-like format
              -s     Display only a short usage synopsis for each pattern

              The return status is 0 unless no command matches pattern.

       history [n]
       history -c
       history -d offset
       history -d start-end
       history -anrw [filename]
       history -p arg [arg ...]
       history -s arg [arg ...]
              With  no  options, display the command history list with line numbers.  Lines listed with a * have
              been modified.   An  argument  of  n  lists  only  the  last  n  lines.   If  the  shell  variable
              HISTTIMEFORMAT  is  set and not null, it is used as a format string for strftime(3) to display the
              time stamp associated with each displayed history entry.  No intervening blank is printed  between
              the formatted time stamp and the history line.  If filename is supplied, it is used as the name of
              the history file; if not, the value of HISTFILE is used.  Options, if supplied, have the following
              meanings:
              -c     Clear the history list by deleting all the entries.
              -d offset
                     Delete  the  history entry at position offset.  If offset 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 history -d command.
              -d start-end
                     Delete  the  history  entries  between  positions  start  and end, inclusive.  Positive and
                     negative values for start and end are interpreted as described above.
              -a     Append the ``new'' history lines to the history file.   These  are  history  lines  entered
                     since  the  beginning  of the current bash session, but not already appended to the history
                     file.
              -n     Read the history lines not already read from the history  file  into  the  current  history
                     list.  These are lines appended to the history file since the beginning of the current bash
                     session.
              -r     Read the contents of the history file and append them to the current history list.
              -w     Write the current history  list  to  the  history  file,  overwriting  the  history  file's
                     contents.
              -p     Perform  history  substitution on the following args and display the result on the standard
                     output.  Does not store the results in the history  list.   Each  arg  must  be  quoted  to
                     disable normal history expansion.
              -s     Store the args in the history list as a single entry.  The last command in the history list
                     is removed before the args are added.

              If the HISTTIMEFORMAT variable is set, the time stamp information  associated  with  each  history
              entry is written to the history file, marked with the history comment character.  When the history
              file is read, lines beginning with the history comment character followed immediately by  a  digit
              are  interpreted  as  timestamps for the following history entry.  The return value is 0 unless an
              invalid option is encountered, an error occurs while reading  or  writing  the  history  file,  an
              invalid  offset is supplied as an argument to -d, or the history expansion supplied as an argument
              to -p fails.

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

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

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

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

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

       local [option] [name[=value] ... | - ]
              For  each argument, a local variable named name is created, and assigned value.  The option can be
              any of the options accepted by declare.  When local is used  within  a  function,  it  causes  the
              variable name to have a visible scope restricted to that function and its children.  If name is -,
              the set of shell options is made local to the function in which local is  invoked:  shell  options
              changed  using  the set builtin inside the function are restored to their original values when the
              function returns.  With no operands, local writes a  list  of  local  variables  to  the  standard
              output.   It  is  an error to use local when not within a function.  The return status is 0 unless
              local is used outside a function, an invalid name is supplied, or name is a readonly variable.

       logout Exit a login shell.

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

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

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

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

       popd [-n] [+n] [-n]
              Removes  entries  from the directory stack.  With no arguments, removes the top directory from the
              stack, and performs a cd to the new top directory.  Arguments, if  supplied,  have  the  following
              meanings:
              -n     Suppresses the normal change of directory when removing directories from the stack, so that
                     only the stack is manipulated.
              +n     Removes the nth entry counting from the left of the list shown by dirs, starting with zero.
                     For example: ``popd +0'' removes the first directory, ``popd +1'' the second.
              -n     Removes  the  nth  entry  counting  from the right of the list shown by dirs, starting with
                     zero.  For example: ``popd -0'' removes the last directory, ``popd -1'' the next to last.

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

       printf [-v var] format [arguments]
              Write the formatted arguments to the standard output under the control  of  the  format.   The  -v
              option  causes  the  output  to  be  assigned to the variable var rather than being printed to the
              standard output.

              The format is a character string which contains three types of objects:  plain  characters,  which
              are  simply  copied to standard output, character escape sequences, which are converted and copied
              to the standard output, and format specifications, each of  which  causes  printing  of  the  next
              successive  argument.   In  addition  to  the  standard  printf(1)  format  specifications, printf
              interprets the following extensions:
              %b     causes printf to expand backslash escape sequences in the  corresponding  argument  in  the
                     same way as echo -e.
              %q     causes  printf to output the corresponding argument in a format that can be reused as shell
                     input.
              %(datefmt)T
                     causes printf to output the date-time string resulting  from  using  datefmt  as  a  format
                     string  for  strftime(3).  The corresponding argument is an integer representing the number
                     of seconds since the epoch.  Two special argument values may be  used:  -1  represents  the
                     current  time,  and  -2  represents  the  time  the  shell  was invoked.  If no argument is
                     specified, conversion behaves as if -1 had been given.  This is an exception to  the  usual
                     printf behavior.

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

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

       pushd [-n] [+n] [-n]
       pushd [-n] [dir]
              Adds a directory to the top of the directory stack, or rotates the stack, making the  new  top  of
              the  stack  the  current  working  directory.   With  no  arguments,  pushd  exchanges the top two
              directories and returns 0, unless the directory stack is empty.  Arguments, if supplied, have  the
              following meanings:
              -n     Suppresses the normal change of directory when rotating or adding directories to the stack,
                     so that only the stack is manipulated.
              +n     Rotates the stack so that the nth directory (counting from the left of the  list  shown  by
                     dirs, starting with zero) is at the top.
              -n     Rotates  the  stack so that the nth directory (counting from the right of the list shown by
                     dirs, starting with zero) is at the top.
              dir    Adds dir to the directory stack at the top, making it the new current working directory  as
                     if it had been supplied as the argument to the cd builtin.

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

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

       read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p  prompt]  [-t  timeout]  [-u  fd]
       [name ...]
              One  line  is read from the standard input, or from the file descriptor fd supplied as an argument
              to the -u option, split into words as described above under Word Splitting, and the first word  is
              assigned  to  the  first  name,  the second word to the second name, and so on.  If there are more
              words than names, the remaining words and their intervening delimiters are assigned  to  the  last
              name.   If  there  are  fewer words read from the input stream than names, the remaining names are
              assigned empty values.  The characters in IFS are used to split the line into words using the same
              rules  the  shell  uses  for  expansion  (described  above  under  Word Splitting).  The backslash
              character (\) may be used to remove any special meaning for the next character read and  for  line
              continuation.  Options, if supplied, have the following meanings:
              -a aname
                     The  words  are  assigned to sequential indices of the array variable aname, starting at 0.
                     aname is unset before any new values are assigned.  Other name arguments are ignored.
              -d delim
                     The first character of delim is used to terminate the input line, rather than newline.   If
                     delim is the empty string, read will terminate a line when it reads a NUL character.
              -e     If  the  standard input is coming from a terminal, readline (see READLINE above) is used to
                     obtain the line.  Readline uses the current (or default, if line editing was not previously
                     active) editing settings, but uses Readline's default filename completion.
              -i text
                     If  readline  is being used to read the line, text is placed into the editing buffer before
                     editing begins.
              -n nchars
                     read returns after reading nchars characters rather than waiting for  a  complete  line  of
                     input,  but  honors  a  delimiter  if  fewer  than  nchars  characters  are read before the
                     delimiter.
              -N nchars
                     read returns after reading exactly nchars characters rather than  waiting  for  a  complete
                     line  of  input,  unless  EOF  is  encountered  or  read  times  out.  Delimiter characters
                     encountered in the input are not treated specially and do not cause read  to  return  until
                     nchars  characters  are read.  The result is not split on the characters in IFS; the intent
                     is that the variable is assigned  exactly  the  characters  read  (with  the  exception  of
                     backslash; see the -r option below).
              -p prompt
                     Display prompt on standard error, without a trailing newline, before attempting to read any
                     input.  The prompt is displayed only if input is coming from a terminal.
              -r     Backslash does not act as an escape character.  The backslash is considered to be  part  of
                     the  line.   In  particular,  a  backslash-newline  pair  may  not  then  be used as a line
                     continuation.
              -s     Silent mode.  If input is coming from a terminal, characters are not echoed.
              -t timeout
                     Cause read to time out and return failure if a complete  line  of  input  (or  a  specified
                     number  of characters) is not read within timeout seconds.  timeout may be a decimal number
                     with a fractional portion following the decimal point.  This option is  only  effective  if
                     read  is  reading input from a terminal, pipe, or other special file; it has no effect when
                     reading from regular files.  If read times out, read saves any partial input read into  the
                     specified variable name.  If timeout is 0, read returns immediately, without trying to read
                     any data.  The exit status is 0 if input is available on  the  specified  file  descriptor,
                     non-zero otherwise.  The exit status is greater than 128 if the timeout is exceeded.
              -u fd  Read input from file descriptor fd.

              If  no  names  are  supplied, the line read is assigned to the variable REPLY.  The exit status is
              zero, unless end-of-file is encountered, read times out (in which case the status is greater  than
              128), a variable assignment error (such as assigning to a readonly variable) occurs, or an invalid
              file descriptor is supplied as the argument to -u.

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

       return [n]
              Causes  a  function  to stop executing and return the value specified by n to its caller.  If n is
              omitted, the return status is that of the last command executed in the function body.   If  return
              is  executed  by a trap handler, the last command used to determine the status is the last command
              executed before the trap handler.  If return is executed during a DEBUG  trap,  the  last  command
              used  to  determine  the status is the last command executed by the trap handler before return was
              invoked.  If return is used outside a function,  but  during  execution  of  a  script  by  the  .
              (source)  command,  it  causes  the shell to stop executing that script and return either n or the
              exit status of the last command executed within the script as the exit status of the script.  If n
              is  supplied,  the return value is its least significant 8 bits.  The return status is non-zero if
              return is supplied a non-numeric argument, or is used outside a function and not during  execution
              of  a  script  by  .  or  source.   Any command associated with the RETURN trap is executed before
              execution resumes after the function or script.

       set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]
       set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg ...]
              Without options, the name and value of each shell variable are displayed in a format that  can  be
              reused  as input for setting or resetting the currently-set variables.  Read-only variables cannot
              be reset.  In posix mode, only shell variables are listed.  The output is sorted according to  the
              current  locale.   When  options are specified, they set or unset shell attributes.  Any arguments
              remaining after option processing are treated as values for  the  positional  parameters  and  are
              assigned, in order, to $1, $2, ...  $n.  Options, if specified, have the following meanings:
              -a      Each  variable  or  function that is created or modified is given the export attribute and
                      marked for export to the environment of subsequent commands.
              -b      Report the status of terminated background jobs immediately, rather than before  the  next
                      primary prompt.  This is effective only when job control is enabled.
              -e      Exit  immediately if a pipeline (which may consist of a single simple command), a list, or
                      a compound command (see SHELL GRAMMAR above), exits with a  non-zero  status.   The  shell
                      does  not exit if the command that fails is part of the command list immediately following
                      a while or until keyword, part of the test following the if or elif reserved  words,  part
                      of  any  command  executed in a && or || list except the command following the final && or
                      ||, any command in a pipeline but the last, or if the  command's  return  value  is  being
                      inverted  with  !.   If a compound command other than a subshell returns a non-zero status
                      because a command failed while -e was being ignored, the shell does not exit.  A  trap  on
                      ERR,  if  set,  is  executed  before  the  shell  exits.  This option applies to the shell
                      environment and each subshell environment separately (see  COMMAND  EXECUTION  ENVIRONMENT
                      above), and may cause subshells to exit before executing all the commands in the subshell.

                      If  a  compound command or shell function executes in a context where -e is being ignored,
                      none of the commands executed within  the  compound  command  or  function  body  will  be
                      affected  by the -e setting, even if -e is set and a command returns a failure status.  If
                      a compound command or shell function sets -e while executing in  a  context  where  -e  is
                      ignored,  that  setting will not have any effect until the compound command or the command
                      containing the function call completes.
              -f      Disable pathname expansion.
              -h      Remember the location of commands as they are looked up for execution.  This is enabled by
                      default.
              -k      All  arguments  in  the  form of assignment statements are placed in the environment for a
                      command, not just those that precede the command name.
              -m      Monitor mode.  Job control is enabled.  This option  is  on  by  default  for  interactive
                      shells  on  systems  that  support  it  (see  JOB  CONTROL above).  All processes run in a
                      separate process group.  When  a  background  job  completes,  the  shell  prints  a  line
                      containing its exit status.
              -n      Read  commands  but  do  not  execute  them.  This may be used to check a shell script for
                      syntax errors.  This is ignored by interactive shells.
              -o option-name
                      The option-name can be one of the following:
                      allexport
                              Same as -a.
                      braceexpand
                              Same as -B.
                      emacs   Use an emacs-style command line editing interface.  This  is  enabled  by  default
                              when  the  shell  is interactive, unless the shell is started with the --noediting
                              option.  This also affects the editing interface used for read -e.
                      errexit Same as -e.
                      errtrace
                              Same as -E.
                      functrace
                              Same as -T.
                      hashall Same as -h.
                      histexpand
                              Same as -H.
                      history Enable command history, as described above under HISTORY.  This option  is  on  by
                              default in interactive shells.
                      ignoreeof
                              The  effect  is  as  if  the shell command ``IGNOREEOF=10'' had been executed (see
                              Shell Variables above).
                      keyword Same as -k.
                      monitor Same as -m.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Currently ignored.
                      notify  Same as -b.
                      nounset Same as -u.
                      onecmd  Same as -t.
                      physical
                              Same as -P.
                      pipefail
                              If set, the return value of a pipeline  is  the  value  of  the  last  (rightmost)
                              command  to  exit  with a non-zero status, or zero if all commands in the pipeline
                              exit successfully.  This option is disabled by default.
                      posix   Change the behavior of bash where the default operation  differs  from  the  POSIX
                              standard  to  match the standard (posix mode).  See SEE ALSO below for a reference
                              to a document that details how posix mode affects bash's behavior.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      vi      Use a vi-style command line editing interface.   This  also  affects  the  editing
                              interface used for read -e.
                      xtrace  Same as -x.
                      If  -o is supplied with no option-name, the values of the current options are printed.  If
                      +o is supplied with no option-name, a series of  set  commands  to  recreate  the  current
                      option settings is displayed on the standard output.
              -p      Turn  on  privileged  mode.  In this mode, the $ENV and $BASH_ENV files are not processed,
                      shell functions are not inherited from  the  environment,  and  the  SHELLOPTS,  BASHOPTS,
                      CDPATH,  and GLOBIGNORE variables, if they appear in the environment, are ignored.  If the
                      shell is started with the effective user (group) id not equal to the real user (group) id,
                      and  the  -p  option is not supplied, these actions are taken and the effective user id is
                      set to the real user id.  If the -p option is supplied at startup, the effective  user  id
                      is  not  reset.  Turning this option off causes the effective user and group ids to be set
                      to the real user and group ids.
              -t      Exit after reading and executing one command.
              -u      Treat unset variables and parameters other than the special parameters "@" and "*"  as  an
                      error when performing parameter expansion.  If expansion is attempted on an unset variable
                      or parameter, the shell prints an error message, and, if not  interactive,  exits  with  a
                      non-zero status.
              -v      Print shell input lines as they are read.
              -x      After  expanding  each  simple  command,  for  command,  case  command, select command, or
                      arithmetic for command, display the expanded value of PS4, followed by the command and its
                      expanded arguments or associated word list.
              -B      The shell performs brace expansion (see Brace Expansion above).  This is on by default.
              -C      If  set,  bash  does  not  overwrite  an  existing file with the >, >&, and <> redirection
                      operators.  This may be overridden when creating output files  by  using  the  redirection
                      operator >| instead of >.
              -E      If  set,  any  trap  on  ERR  is  inherited by shell functions, command substitutions, and
                      commands executed in a subshell environment.  The ERR trap is normally  not  inherited  in
                      such cases.
              -H      Enable  !   style  history  substitution.   This option is on by default when the shell is
                      interactive.
              -P      If set, the shell does not resolve symbolic links when executing commands such as cd  that
                      change  the  current working directory.  It uses the physical directory structure instead.
                      By default, bash follows the logical chain of directories when performing  commands  which
                      change the current directory.
              -T      If  set,  any  traps  on  DEBUG  and  RETURN  are  inherited  by  shell functions, command
                      substitutions, and commands executed in a subshell  environment.   The  DEBUG  and  RETURN
                      traps are normally not inherited in such cases.
              --      If  no arguments follow this option, then the positional parameters are unset.  Otherwise,
                      the positional parameters are set to the args, even if some of them begin with a -.
              -       Signal the end of options, cause all remaining args  to  be  assigned  to  the  positional
                      parameters.   The  -x and -v options are turned off.  If there are no args, the positional
                      parameters remain unchanged.

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

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

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

              If either -s or -u is used with no optname arguments, shopt shows only those options which are set
              or  unset,  respectively.   Unless  otherwise  noted,  the  shopt  options are disabled (unset) by
              default.

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

              The list of shopt options is:

              assoc_expand_once
                      If set, the shell suppresses multiple evaluation of associative  array  subscripts  during
                      arithmetic  expression  evaluation,  while  executing  builtins  that can perform variable
                      assignments, and while executing builtins that perform array dereferencing.
              autocd  If set, a command name that is the name of a directory is  executed  as  if  it  were  the
                      argument to the cd command.  This option is only used by interactive shells.
              cdable_vars
                      If set, an argument to the cd builtin command that is not a directory is assumed to be the
                      name of a variable whose value is the directory to change to.
              cdspell If set, minor errors in the spelling of a directory component in  a  cd  command  will  be
                      corrected.  The errors checked for are transposed characters, a missing character, and one
                      character too many.  If a correction is found, the corrected filename is printed, and  the
                      command proceeds.  This option is only used by interactive shells.
              checkhash
                      If set, bash checks that a command found in the hash table exists before trying to execute
                      it.  If a hashed command no longer exists, a normal path search is performed.
              checkjobs
                      If set, bash lists  the  status  of  any  stopped  and  running  jobs  before  exiting  an
                      interactive  shell.   If any jobs are running, this causes the exit to be deferred until a
                      second exit is attempted without an intervening command  (see  JOB  CONTROL  above).   The
                      shell always postpones exiting if any jobs are stopped.
              checkwinsize
                      If  set,  bash  checks  the  window size after each external (non-builtin) command and, if
                      necessary, updates the values of LINES and COLUMNS.  This option is enabled by default.
              cmdhist If set, bash attempts to save all lines of a multiple-line command  in  the  same  history
                      entry.   This  allows  easy  re-editing of multi-line commands.  This option is enabled by
                      default, but only has an effect if command history is enabled, as  described  above  under
                      HISTORY.
              compat31
                      If  set, bash changes its behavior to that of version 3.1 with respect to quoted arguments
                      to the [[ conditional command's =~ operator and  locale-specific  string  comparison  when
                      using the [[ conditional command's < and > operators.  Bash versions prior to bash-4.1 use
                      ASCII collation and strcmp(3); bash-4.1 and  later  use  the  current  locale's  collation
                      sequence and strcoll(3).
              compat32
                      If  set,  bash changes its behavior to that of version 3.2 with respect to locale-specific
                      string comparison when using the [[ conditional command's < and > operators (see  previous
                      item)  and  the  effect  of  interrupting  a  command list.  Bash versions 3.2 and earlier
                      continue with the next command in the list after one terminates due to an interrupt.
              compat40
                      If set, bash changes its behavior to that of version 4.0 with respect  to  locale-specific
                      string  comparison  when  using  the  [[  conditional  command's  <  and  > operators (see
                      description of compat31) and the effect of interrupting a command list.  Bash versions 4.0
                      and  later  interrupt  the  list as if the shell received the interrupt; previous versions
                      continue with the next command in the list.
              compat41
                      If set, bash, when in posix mode, treats a  single  quote  in  a  double-quoted  parameter
                      expansion  as  a special character.  The single quotes must match (an even number) and the
                      characters between the single quotes are considered quoted.  This is the behavior of posix
                      mode through version 4.1.  The default bash behavior remains as in previous versions.
              compat42
                      If  set,  bash  does  not  process the replacement string in the pattern substitution word
                      expansion using quote removal.
              compat43
                      If set, bash does not print a warning message if an  attempt  is  made  to  use  a  quoted
                      compound array assignment as an argument to declare, makes word expansion errors non-fatal
                      errors that cause the current command to fail (the default behavior is to make them  fatal
                      errors  that  cause  the  shell  to  exit), and does not reset the loop state when a shell
                      function is executed (this allows break or continue in a shell function to affect loops in
                      the caller's context).
              compat44
                      If  set,  bash  saves the positional parameters to BASH_ARGV and BASH_ARGC before they are
                      used, regardless of whether or not extended debugging mode is enabled.
              complete_fullquote
                      If set, bash quotes all  shell  metacharacters  in  filenames  and  directory  names  when
                      performing  completion.   If  not set, bash removes metacharacters such as the dollar sign
                      from the set of  characters  that  will  be  quoted  in  completed  filenames  when  these
                      metacharacters  appear  in shell variable references in words to be completed.  This means
                      that dollar signs in variable names  that  expand  to  directories  will  not  be  quoted;
                      however,  any  dollar  signs  appearing  in filenames will not be quoted, either.  This is
                      active only when bash is using backslashes to quote completed filenames.  This variable is
                      set by default, which is the default bash behavior in versions through 4.2.
              direxpand
                      If  set,  bash replaces directory names with the results of word expansion when performing
                      filename completion.  This changes the contents of the readline editing  buffer.   If  not
                      set, bash attempts to preserve what the user typed.
              dirspell
                      If set, bash attempts spelling correction on directory names during word completion if the
                      directory name initially supplied does not exist.
              dotglob If set, bash includes filenames beginning with a `.' in the results of pathname expansion.
                      The  filenames  ``.''   and  ``..''  must always be matched explicitly, even if dotglob is
                      set.
              execfail
                      If set, a non-interactive shell will not exit if it cannot execute the file  specified  as
                      an  argument  to  the  exec  builtin  command.  An interactive shell does not exit if exec
                      fails.
              expand_aliases
                      If set, aliases are expanded as described above under ALIASES.  This option is enabled  by
                      default for interactive shells.
              extdebug
                      If  set  at  shell  invocation,  arrange  to execute the debugger profile before the shell
                      starts, identical to the --debugger option.  If set after  invocation,  behavior  intended
                      for use by debuggers is enabled:
                      1.     The  -F option to the declare builtin displays the source file name and line number
                             corresponding to each function name supplied as an argument.
                      2.     If the command run by the DEBUG trap returns a non-zero value, the next command  is
                             skipped and not executed.
                      3.     If  the  command  run  by  the  DEBUG  trap  returns a value of 2, and the shell is
                             executing in a subroutine (a shell function or a shell script executed by the .  or
                             source builtins), the shell simulates a call to return.
                      4.     BASH_ARGC and BASH_ARGV are updated as described in their descriptions above.
                      5.     Function  tracing  is enabled: command substitution, shell functions, and subshells
                             invoked with ( command ) inherit the DEBUG and RETURN traps.
                      6.     Error tracing is enabled: command  substitution,  shell  functions,  and  subshells
                             invoked with ( command ) inherit the ERR trap.
              extglob If  set,  the  extended pattern matching features described above under Pathname Expansion
                      are enabled.
              extquote
                      If set, $'string' and  $"string"  quoting  is  performed  within  ${parameter}  expansions
                      enclosed in double quotes.  This option is enabled by default.
              failglob
                      If  set,  patterns  which  fail  to match filenames during pathname expansion result in an
                      expansion error.
              force_fignore
                      If set, the suffixes specified by the FIGNORE shell variable cause  words  to  be  ignored
                      when  performing  word  completion  even  if  the  ignored  words  are  the  only possible
                      completions.  See SHELL VARIABLES above for a description  of  FIGNORE.   This  option  is
                      enabled by default.
              globasciiranges
                      If  set,  range  expressions  used  in  pattern  matching bracket expressions (see Pattern
                      Matching above) behave as if in the traditional  C  locale  when  performing  comparisons.
                      That  is, the current locale's collating sequence is not taken into account, so b will not
                      collate between A and B, and upper-case  and  lower-case  ASCII  characters  will  collate
                      together.
              globstar
                      If  set, the pattern ** used in a pathname expansion context will match all files and zero
                      or more directories and  subdirectories.   If  the  pattern  is  followed  by  a  /,  only
                      directories and subdirectories match.
              gnu_errfmt
                      If set, shell error messages are written in the standard GNU error message format.
              histappend
                      If  set,  the  history  list  is  appended  to the file named by the value of the HISTFILE
                      variable when the shell exits, rather than overwriting the file.
              histreedit
                      If set, and readline is being used, a user is given the opportunity to  re-edit  a  failed
                      history substitution.
              histverify
                      If  set,  and  readline  is  being  used,  the  results  of  history  substitution are not
                      immediately passed to the shell parser.  Instead, the resulting line is  loaded  into  the
                      readline editing buffer, allowing further modification.
              hostcomplete
                      If  set, and readline is being used, bash will attempt to perform hostname completion when
                      a word containing a @ is being completed (see Completing under READLINE above).   This  is
                      enabled by default.
              huponexit
                      If set, bash will send SIGHUP to all jobs when an interactive login shell exits.
              inherit_errexit
                      If  set,  command  substitution  inherits  the  value  of  the  errexit option, instead of
                      unsetting it in the subshell environment.  This option  is  enabled  when  posix  mode  is
                      enabled.
              interactive_comments
                      If  set,  allow a word beginning with # to cause that word and all remaining characters on
                      that line to be ignored in an interactive shell (see  COMMENTS  above).   This  option  is
                      enabled by default.
              lastpipe
                      If  set,  and job control is not active, the shell runs the last command of a pipeline not
                      executed in the background in the current shell environment.
              lithist If set, and the cmdhist option is enabled, multi-line commands are saved  to  the  history
                      with embedded newlines rather than using semicolon separators where possible.
              localvar_inherit
                      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  attribute
                      is not inherited.
              localvar_unset
                      If  set,  calling  unset  on  local  variables  in  previous function scopes marks them so
                      subsequent lookups find them unset until that function returns. This is identical  to  the
                      behavior of unsetting local variables at the current function scope.
              login_shell
                      The  shell sets this option if it is started as a login shell (see INVOCATION above).  The
                      value may not be changed.
              mailwarn
                      If set, and a file that bash is checking for mail has been accessed since the last time it
                      was checked, the message ``The mail in mailfile has been read'' is displayed.
              no_empty_cmd_completion
                      If  set, and readline is being used, bash will not attempt to search the PATH for possible
                      completions when completion is attempted on an empty line.
              nocaseglob
                      If set, bash matches filenames in a  case-insensitive  fashion  when  performing  pathname
                      expansion (see Pathname Expansion above).
              nocasematch
                      If set, bash matches patterns in a case-insensitive fashion when performing matching while
                      executing case or [[ conditional  commands,  when  performing  pattern  substitution  word
                      expansions, or when filtering possible completions as part of programmable completion.
              nullglob
                      If set, bash allows patterns which match no files (see Pathname Expansion above) to expand
                      to a null string, rather than themselves.
              progcomp
                      If set, the programmable completion facilities (see  Programmable  Completion  above)  are
                      enabled.  This option is enabled by default.
              progcomp_alias
                      If  set,  and  programmable completion is enabled, bash treats a command name that doesn't
                      have any completions as a possible alias and attempts alias expansion. If it has an alias,
                      bash  attempts  programmable completion using the command word resulting from the expanded
                      alias.
              promptvars
                      If set, prompt strings  undergo  parameter  expansion,  command  substitution,  arithmetic
                      expansion,  and  quote removal after being expanded as described in PROMPTING above.  This
                      option is enabled by default.
              restricted_shell
                      The shell sets this option if it is started  in  restricted  mode  (see  RESTRICTED  SHELL
                      below).   The  value  may  not  be  changed.  This is not reset when the startup files are
                      executed, allowing the startup files to discover whether or not a shell is restricted.
              shift_verbose
                      If set, the shift builtin prints an error message when the shift count exceeds the  number
                      of positional parameters.
              sourcepath
                      If set, the source (.) builtin uses the value of PATH to find the directory containing the
                      file supplied as an argument.  This option is enabled by default.
              xpg_echo
                      If set, the echo builtin expands backslash-escape sequences by default.

       suspend [-f]
              Suspend the execution of this shell until it receives a SIGCONT signal.  A login shell  cannot  be
              suspended; the -f option can be used to override this and force the suspension.  The return status
              is 0 unless the shell is a login shell and -f is not supplied, or if job control is not enabled.

       test expr
       [ expr ]
              Return a status of 0 (true) or 1 (false) depending on the evaluation of the conditional expression
              expr.   Each  operator  and  operand must be a separate argument.  Expressions are composed of the
              primaries described above under CONDITIONAL EXPRESSIONS.  test does not accept  any  options,  nor
              does it accept and ignore an argument of -- as signifying the end of options.

              Expressions  may  be  combined  using  the  following  operators,  listed  in  decreasing order of
              precedence.  The evaluation depends on the number of arguments; see below.  Operator precedence is
              used when there are five or more arguments.
              ! expr True if expr is false.
              ( expr )
                     Returns  the  value  of  expr.   This  may  be  used  to  override the normal precedence of
                     operators.
              expr1 -a expr2
                     True if both expr1 and expr2 are true.
              expr1 -o expr2
                     True if either expr1 or expr2 is true.

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

              0 arguments
                     The expression is false.
              1 argument
                     The expression is true if and only if the argument is not null.
              2 arguments
                     If the first argument is !, the expression is true if and only if the  second  argument  is
                     null.   If  the first argument is one of the unary conditional operators listed above under
                     CONDITIONAL EXPRESSIONS, the expression is true if the unary test is true.   If  the  first
                     argument is not a valid unary conditional operator, the expression is false.
              3 arguments
                     The following conditions are applied in the order listed.  If the second argument is one of
                     the binary conditional operators listed above under CONDITIONAL EXPRESSIONS, the result  of
                     the  expression  is  the  result  of the binary test using the first and third arguments as
                     operands.  The -a and -o operators are considered binary operators  when  there  are  three
                     arguments.   If the first argument is !, the value is the negation of the two-argument test
                     using the second and third arguments.  If the first argument is exactly  (  and  the  third
                     argument  is  exactly  ),  the  result  is  the  one-argument  test of the second argument.
                     Otherwise, the expression is false.
              4 arguments
                     If the first argument is !, the result is the negation  of  the  three-argument  expression
                     composed  of  the  remaining  arguments.  Otherwise, the expression is parsed and evaluated
                     according to precedence using the rules listed above.
              5 or more arguments
                     The expression is parsed and evaluated according  to  precedence  using  the  rules  listed
                     above.

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

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

       trap [-lp] [[arg] sigspec ...]
              The command arg is to be read and executed when the shell receives signal(s) sigspec.  If  arg  is
              absent  (and  there  is  a  single  sigspec)  or -, each specified signal is reset to its original
              disposition (the value it had upon entrance to the shell).  If arg is the null string  the  signal
              specified  by  each sigspec is ignored by the shell and by the commands it invokes.  If arg is not
              present and -p has been supplied,  then  the  trap  commands  associated  with  each  sigspec  are
              displayed.   If no arguments are supplied or if only -p is given, trap prints the list of commands
              associated with each signal.  The -l option causes the shell to print a list of signal  names  and
              their  corresponding  numbers.   Each  sigspec is either a signal name defined in <signal.h>, or a
              signal number.  Signal names are case insensitive and the SIG prefix is optional.

              If a sigspec is EXIT (0) the command arg is executed on exit from the  shell.   If  a  sigspec  is
              DEBUG,  the command arg is executed before every simple command, for command, case command, select
              command, every arithmetic for command, and before the first command executes in a  shell  function
              (see  SHELL  GRAMMAR above).  Refer to the description of the extdebug option to the shopt builtin
              for details of its effect on the DEBUG trap.  If a sigspec is RETURN, the command arg is  executed
              each time a shell function or a script executed with the . or source builtins finishes executing.

              If  a  sigspec  is  ERR,  the  command arg is executed whenever a pipeline (which may consist of a
              single simple command), a list, or a compound command returns a non-zero exit status,  subject  to
              the  following  conditions.   The  ERR  trap  is not executed if the failed command is part of the
              command list immediately following a while or until keyword, part of the test in an if  statement,
              part of a command executed in a && or || list except the command following the final && or ||, any
              command in a pipeline but the last, or if the command's return value is being  inverted  using  !.
              These are the same conditions obeyed by the errexit (-e) option.

              Signals  ignored upon entry to the shell cannot be trapped or reset.  Trapped signals that are not
              being ignored are reset to their original values in a subshell or subshell environment when one is
              created.  The return status is false if any sigspec is invalid; otherwise trap returns true.

       type [-aftpP] name [name ...]
              With no options, indicate how each name would be interpreted if used as a command name.  If the -t
              option is used, type prints a string which is one of alias, keyword, function, builtin, or file if
              name is an alias, shell reserved word, function, builtin, or disk file, respectively.  If the name
              is not found, then nothing is printed, and an exit status of false is returned.  If the -p  option
              is  used,  type  either  returns  the  name  of  the disk file that would be executed if name were
              specified as a command name, or nothing if ``type -t name'' would not return file.  The -P  option
              forces  a PATH search for each name, even if ``type -t name'' would not return file.  If a command
              is hashed, -p and -P print the hashed value, which is not necessarily the file that appears  first
              in PATH.  If the -a option is used, type prints all of the places that contain an executable named
              name.  This includes aliases and functions, if and only if the -p option is not  also  used.   The
              table  of hashed commands is not consulted when using -a.  The -f option suppresses shell function
              lookup, as with the command builtin.  type returns true if all of the arguments are  found,  false
              if any are not found.

       ulimit [-HSabcdefiklmnpqrstuvxPT [limit]]
              Provides  control  over  the  resources  available to the shell and to processes started by it, on
              systems that allow such control.  The -H and -S options specify that the hard or soft limit is set
              for  the  given  resource.   A hard limit cannot be increased by a non-root user once it is set; a
              soft limit may be increased up to the value of the hard limit.  If neither -H nor -S is specified,
              both  the  soft and hard limits are set.  The value of limit can be a number in the unit specified
              for the resource or one of the special values hard,  soft,  or  unlimited,  which  stand  for  the
              current  hard limit, the current soft limit, and no limit, respectively.  If limit is omitted, the
              current value of the soft limit of the resource is printed, unless the -H option is  given.   When
              more  than one resource is specified, the limit name and unit are printed before the value.  Other
              options are interpreted as follows:
              -a     All current limits are reported
              -b     The maximum socket buffer size
              -c     The maximum size of core files created
              -d     The maximum size of a process's data segment
              -e     The maximum scheduling priority ("nice")
              -f     The maximum size of files written by the shell and its children
              -i     The maximum number of pending signals
              -k     The maximum number of kqueues that may be allocated
              -l     The maximum size that may be locked into memory
              -m     The maximum resident set size (many systems do not honor this limit)
              -n     The maximum number of open file descriptors (most systems do not allow  this  value  to  be
                     set)
              -p     The pipe size in 512-byte blocks (this may not be set)
              -q     The maximum number of bytes in POSIX message queues
              -r     The maximum real-time scheduling priority
              -s     The maximum stack size
              -t     The maximum amount of cpu time in seconds
              -u     The maximum number of processes available to a single user
              -v     The  maximum  amount  of virtual memory available to the shell and, on some systems, to its
                     children
              -x     The maximum number of file locks
              -P     The maximum number of pseudoterminals
              -T     The maximum number of threads

              If limit is given, and the -a option is not  used,  limit  is  the  new  value  of  the  specified
              resource.   If no option is given, then -f is assumed.  Values are in 1024-byte increments, except
              for -t, which is in seconds; -p, which is in units of 512-byte blocks; -P, -T, -b, -k, -n, and -u,
              which  are  unscaled values; and, when in posix mode, -c and -f, which are in 512-byte increments.
              The return status is 0 unless an invalid option or argument is supplied, or an error occurs  while
              setting a new limit.

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

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

       unset [-fv] [-n] [name ...]
              For each name, remove the corresponding variable or function.  If the -v  option  is  given,  each
              name  refers  to  a  shell variable, and that variable is removed.  Read-only variables may not be
              unset.  If -f is specified, each name refers to a shell function, and the function  definition  is
              removed.   If  the  -n option is supplied, and name is a variable with the nameref attribute, name
              will be unset rather than the variable it references.  -n has  no  effect  if  the  -f  option  is
              supplied.   If no options are supplied, each name refers to a variable; if there is no variable by
              that name, any function with that name is unset.  Each unset variable or function is removed  from
              the  environment  passed  to  subsequent  commands.   If  any of COMP_WORDBREAKS, RANDOM, SECONDS,
              LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their special properties, even
              if they are subsequently reset.  The exit status is true unless a name is readonly.

       wait [-fn] [id ...]
              Wait for each specified child process and return its termination status.  Each id 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  id  is  not  given, all currently active child processes are waited for, and the return
              status is zero.  If the -n option is supplied, wait waits for any job to terminate and returns its
              exit  status.   If  the  -f  option  is  supplied,  and  job control is enabled, wait forces id to
              terminate before returning its status, instead  of  returning  when  it  changes  status.   If  id
              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.

ZOBACZ TAKŻE

       bash(1), sh(1)