GNU.WIKI: The GNU/Linux Knowledge Base

  [HOME] [PHP Manual] [HowTo] [ABS] [MAN1] [MAN2] [MAN3] [MAN4] [MAN5] [MAN6] [MAN7] [MAN8] [MAN9]

  [0-9] [Aa] [Bb] [Cc] [Dd] [Ee] [Ff] [Gg] [Hh] [Ii] [Jj] [Kk] [Ll] [Mm] [Nn] [Oo] [Pp] [Qq] [Rr] [Ss] [Tt] [Uu] [Vv] [Ww] [Xx] [Yy] [Zz]


NAME

       bash - GNU Bourne-Again SHell

SYNOPSIS

       bash [options] [command_string | file]

COPYRIGHT

       Bash is Copyright (C) 1989-2013 by the Free Software Foundation, Inc.

DESCRIPTION

       Bash  is  an  sh-compatible  command language interpreter that executes
       commands read from the standard  input  or  from  a  file.   Bash  also
       incorporates useful features from the Korn and C shells (ksh and csh).

       Bash  is  intended  to  be a conformant implementation of the Shell and
       Utilities portion  of  the  IEEE  POSIX  specification  (IEEE  Standard
       1003.1).  Bash can be configured to be POSIX-conformant by default.

OPTIONS

       All   of   the    single-character  shell  options  documented  in  the
       description of the set builtin command can be used as options when  the
       shell  is  invoked.  In addition, bash interprets the following options
       when it is invoked:

       -c        If the -c option is present, then commands are read from  the
                 first  non-option  argument  command_string.   If  there  are
                 arguments after the command_string, they are assigned to  the
                 positional parameters, starting with $0.
       -i        If the -i option is present, the shell is interactive.
       -l        Make bash act as if it had been invoked as a login shell (see
                 INVOCATION below).
       -r        If the -r option is present,  the  shell  becomes  restricted
                 (see RESTRICTED SHELL below).
       -s        If  the -s option is present, or if no arguments remain after
                 option processing, then commands are read from  the  standard
                 input.   This  option  allows the positional parameters to be
                 set when invoking an interactive shell.
       -D        A list of all double-quoted strings preceded by $ is  printed
                 on  the  standard  output.   These  are  the strings that are
                 subject to language translation when the  current  locale  is
                 not C or POSIX.  This implies the -n option; no commands will
                 be executed.
       [-+]O [shopt_option]
                 shopt_option is one of the  shell  options  accepted  by  the
                 shopt   builtin  (see  SHELL  BUILTIN  COMMANDS  below).   If
                 shopt_option is present, -O sets the value of that option; +O
                 unsets  it.   If  shopt_option is not supplied, the names and
                 values of the shell options accepted by shopt are printed  on
                 the  standard  output.   If  the invocation option is +O, the
                 output is displayed in a format that may be reused as input.
       --        A -- signals the end of options and disables  further  option
                 processing.   Any  arguments  after  the  --  are  treated as
                 filenames and arguments.  An argument of - is  equivalent  to
                 --.

       Bash  also  interprets  a  number  of  multi-character  options.  These
       options must appear on the command  line  before  the  single-character
       options to be recognized.

       --debugger
              Arrange for the debugger profile to be executed before the shell
              starts.  Turns on extended debugging mode (see  the  description
              of the extdebug option to the shopt builtin below).
       --dump-po-strings
              Equivalent  to  -D,  but  the  output  is  in the GNU gettext po
              (portable object) file format.
       --dump-strings
              Equivalent to -D.
       --help Display  a  usage  message   on   standard   output   and   exit
              successfully.
       --init-file file
       --rcfile file
              Execute   commands   from   file  instead  of  the  system  wide
              initialization file /etc/bash.bashrc and the  standard  personal
              initialization  file  ~/.bashrc if the shell is interactive (see
              INVOCATION below).

       --login
              Equivalent to -l.

       --noediting
              Do not use the GNU readline library to read command  lines  when
              the shell is interactive.

       --noprofile
              Do  not read either the system-wide startup file /etc/profile or
              any  of  the  personal  initialization  files   ~/.bash_profile,
              ~/.bash_login,  or  ~/.profile.   By  default,  bash reads these
              files when it is  invoked  as  a  login  shell  (see  INVOCATION
              below).

       --norc Do  not  read  and  execute  the system wide initialization file
              /etc/bash.bashrc and the personal initialization file  ~/.bashrc
              if  the  shell  is interactive.  This option is on by default if
              the shell is invoked as sh.

       --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.

       --restricted
              The shell becomes restricted (see RESTRICTED SHELL below).

       --verbose
              Equivalent to  -v.

       --version
              Show  version  information  for  this  instance  of  bash on the
              standard output and exit successfully.

ARGUMENTS

       If arguments remain after option processing, and neither the -c nor the
       -s  option  has  been supplied, the first argument is assumed to be the
       name of a file containing shell commands.  If bash is invoked  in  this
       fashion,  $0  is  set  to  the  name  of  the  file, and the positional
       parameters are set to the remaining arguments.  Bash reads and executes
       commands  from  this  file, then exits.  Bash's exit status is the exit
       status of the last command executed in the script.  If no commands  are
       executed,  the  exit status is 0.  An attempt is first made to open the
       file in the current directory, and, if no file is found, then the shell
       searches the directories in PATH for the script.

INVOCATION

       A  login shell is one whose first character of argument zero is a -, or
       one started with the --login option.

       An interactive shell is one started without  non-option  arguments  and
       without the -c option whose standard input and error are both connected
       to terminals (as determined by isatty(3)), or one started with  the  -i
       option.   PS1 is set and $- includes i if bash is interactive, allowing
       a shell script or a startup file to test this state.

       The following paragraphs describe how bash executes its startup  files.
       If  any  of  the files exist but cannot be read, bash reports an error.
       Tildes are  expanded  in  filenames  as  described  below  under  Tilde
       Expansion in the EXPANSION section.

       When  bash  is  invoked  as  an  interactive  login shell, or as a non-
       interactive shell with the --login option, it first reads and  executes
       commands  from  the  file  /etc/profile,  if  that  file exists.  After
       reading that file, it looks  for  ~/.bash_profile,  ~/.bash_login,  and
       ~/.profile,  in  that  order,  and reads and executes commands from the
       first one that exists and is readable.  The --noprofile option  may  be
       used when the shell is started to inhibit this behavior.

       When  a  login  shell  exits, bash reads and executes commands from the
       file ~/.bash_logout, if it exists.

       When an interactive shell that is not a login shell  is  started,  bash
       reads  and  executes  commands  from /etc/bash.bashrc and ~/.bashrc, if
       these files exist.  This may be inhibited by using the  --norc  option.
       The  --rcfile  file option will force bash to read and execute commands
       from file instead of /etc/bash.bashrc and ~/.bashrc.

       When bash is started non-interactively, to  run  a  shell  script,  for
       example, it looks for the variable BASH_ENV in the environment, expands
       its value if it appears there, and uses the expanded value as the  name
       of  a  file  to  read  and  execute.   Bash behaves as if the following
       command were executed:
              if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
       but the value of the PATH variable  is  not  used  to  search  for  the
       filename.

       If  bash  is  invoked  with  the name sh, it tries to mimic the startup
       behavior of historical versions of sh as  closely  as  possible,  while
       conforming  to  the  POSIX  standard  as  well.   When  invoked  as  an
       interactive login shell, or a non-interactive shell  with  the  --login
       option,   it   first   attempts  to  read  and  execute  commands  from
       /etc/profile and ~/.profile, in that order.  The --noprofile option may
       be used to inhibit this behavior.  When invoked as an interactive shell
       with the name sh, bash looks for the variable ENV, expands its value if
       it  is  defined,  and  uses the expanded value as the name of a file to
       read and execute.  Since a shell invoked as sh does not attempt to read
       and  execute commands from any other startup files, the --rcfile option
       has no effect.  A non-interactive shell invoked with the name  sh  does
       not  attempt to read any other startup files.  When invoked as sh, bash
       enters posix mode after the startup files are read.

       When bash is started in posix mode, as with the  --posix  command  line
       option, it follows the POSIX standard for startup files.  In this mode,
       interactive shells expand the ENV variable and commands  are  read  and
       executed  from  the  file  whose  name is the expanded value.  No other
       startup files are read.

       Bash attempts to determine when it is being run with its standard input
       connected to a network connection, as when executed by the remote shell
       daemon, usually rshd,  or  the  secure  shell  daemon  sshd.   If  bash
       determines  it  is  being  run  in  this fashion, it reads and executes
       commands from ~/.bashrc and ~/.bashrc, if these  files  exist  and  are
       readable.  It will not do this if invoked as sh.  The --norc option may
       be used to inhibit this behavior, and the --rcfile option may  be  used
       to  force  another file to be read, but neither rshd nor sshd generally
       invoke the shell with those options or allow them to be specified.

       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, no startup
       files are read, shell functions are not inherited from the environment,
       the  SHELLOPTS,  BASHOPTS,  CDPATH,  and  GLOBIGNORE variables, if they
       appear in the environment, are ignored, and the effective  user  id  is
       set  to  the real user id.  If the -p option is supplied at invocation,
       the startup behavior is the same, but the  effective  user  id  is  not
       reset.

DEFINITIONS

       The  following  definitions  are  used  throughout  the  rest  of  this
       document.
       blank  A space or tab.
       word   A sequence of characters considered as  a  single  unit  by  the
              shell.  Also known as a token.
       name   A   word   consisting   only   of  alphanumeric  characters  and
              underscores, and beginning with an alphabetic  character  or  an
              underscore.  Also referred to as an identifier.
       metacharacter
              A  character  that,  when unquoted, separates words.  One of the
              following:
              |  & ; ( ) < > space tab
       control operator
              A token that performs a control function.   It  is  one  of  the
              following symbols:
              || & && ; ;; ( ) | |& <newline>

RESERVED WORDS

       Reserved words are words that have a special meaning to the shell.  The
       following words are recognized as reserved when unquoted and either the
       first  word  of a simple command (see SHELL GRAMMAR below) or the third
       word of a case or for command:

       ! case  coproc  do done elif else esac fi for  function  if  in  select
       then until while { } time [[ ]]

SHELL GRAMMAR

   Simple Commands
       A  simple  command  is  a  sequence  of  optional  variable assignments
       followed by blank-separated words and redirections, and terminated by a
       control operator.  The first word specifies the command to be executed,
       and is passed as argument zero.  The  remaining  words  are  passed  as
       arguments to the invoked command.

       The  return  value  of a simple command is its exit status, or 128+n if
       the command is terminated by signal n.

   Pipelines
       A pipeline is a sequence of one or more commands separated  by  one  of
       the control operators | or |&.  The format for a pipeline is:

              [time [-p]] [ ! ] command [ [|⎪|&] command2 ... ]

       The  standard output of command is connected via a pipe to the standard
       input  of  command2.   This  connection   is   performed   before   any
       redirections  specified  by the command (see REDIRECTION below).  If |&
       is used, command's standard error, in addition to its standard  output,
       is  connected  to  command2's  standard  input  through the pipe; it is
       shorthand for 2>&1 |.  This implicit redirection of the standard  error
       to the standard output is performed after any redirections specified by
       the command.

       The return status of a pipeline is the exit status of the last command,
       unless  the  pipefail  option  is enabled.  If pipefail is enabled, the
       pipeline's return status is the value of the last  (rightmost)  command
       to  exit  with  a  non-zero  status,  or  zero  if  all  commands  exit
       successfully.  If the reserved word !  precedes a  pipeline,  the  exit
       status  of  that pipeline is the logical negation of the exit status as
       described above.  The shell waits for all commands in the  pipeline  to
       terminate before returning a value.

       If  the  time reserved word precedes a pipeline, the elapsed as well as
       user and system time consumed by its execution are  reported  when  the
       pipeline  terminates.   The -p option changes the output format to that
       specified by POSIX.  When the shell is  in  posix  mode,  it  does  not
       recognize  time as a reserved word if the next token begins with a `-'.
       The TIMEFORMAT variable may be set to a format  string  that  specifies
       how  the timing information should be displayed; see the description of
       TIMEFORMAT under Shell Variables below.

       When the shell is in posix mode, time may be followed by a newline.  In
       this  case,  the shell displays the total user and system time consumed
       by the shell and its children.  The TIMEFORMAT variable may be used  to
       specify the format of the time information.

       Each  command in a pipeline is executed as a separate process (i.e., in
       a subshell).

   Lists
       A list is a sequence of one or more pipelines separated by one  of  the
       operators ;, &, &&, or ||, and optionally terminated by one of ;, &, or
       <newline>.

       Of these list operators, && and || have equal precedence, followed by ;
       and &, which have equal precedence.

       A  sequence  of  one or more newlines may appear in a list instead of a
       semicolon to delimit commands.

       If a command is  terminated  by  the  control  operator  &,  the  shell
       executes  the  command in the background in a subshell.  The shell does
       not wait for the command  to  finish,  and  the  return  status  is  0.
       Commands  separated  by  a ; are executed sequentially; the shell waits
       for each command to terminate in turn.  The return status is  the  exit
       status of the last command executed.

       AND  and  OR  lists are sequences of one of more pipelines separated by
       the && and || control operators, respectively.  AND and  OR  lists  are
       executed with left associativity.  An AND list has the form

              command1 && command2

       command2  is  executed if, and only if, command1 returns an exit status
       of zero.

       An OR list has the form

              command1 || command2

       command2 is executed if and only if command1 returns  a  non-zero  exit
       status.   The  return  status of AND and OR lists is the exit status of
       the last command executed in the list.

   Compound Commands
       A compound command is one of the following.  In most cases a list in  a
       command's  description may be separated from the rest of the command by
       one or more newlines, and may be followed by a newline in  place  of  a
       semicolon.

       (list) list   is  executed  in  a  subshell  environment  (see  COMMAND
              EXECUTION ENVIRONMENT below).  Variable assignments and  builtin
              commands  that  affect  the shell's environment do not remain in
              effect after the command completes.  The return  status  is  the
              exit status of list.

       { list; }
              list  is simply executed in the current shell environment.  list
              must be terminated with a newline or semicolon.  This  is  known
              as  a  group  command.   The return status is the exit status of
              list.  Note that unlike the metacharacters ( and ), { and }  are
              reserved words and must occur where a reserved word is permitted
              to be recognized.  Since they do not cause a  word  break,  they
              must  be  separated  from  list  by  whitespace or another shell
              metacharacter.

       ((expression))
              The expression is evaluated according  to  the  rules  described
              below   under  ARITHMETIC  EVALUATION.   If  the  value  of  the
              expression is non-zero, the return status is  0;  otherwise  the
              return   status  is  1.   This  is  exactly  equivalent  to  let
              "expression".

       [[ expression ]]
              Return a status of 0 or 1 depending on  the  evaluation  of  the
              conditional  expression expression.  Expressions are composed of
              the primaries described  below  under  CONDITIONAL  EXPRESSIONS.
              Word  splitting  and pathname expansion are not performed on the
              words between the [[ and  ]];  tilde  expansion,  parameter  and
              variable  expansion, arithmetic expansion, command substitution,
              process  substitution,  and   quote   removal   are   performed.
              Conditional  operators  such  as  -f  must  be  unquoted  to  be
              recognized as primaries.

              When used with [[, the < and > operators sort  lexicographically
              using the current locale.

       See  the description of the test builtin command (section SHELL BUILTIN
       COMMANDS  below)  for  the  handling  of  parameters   (i.e.    missing
       parameters).

       When  the  == and != operators are used, the string to the right of the
       operator is considered a pattern and matched  according  to  the  rules
       described  below under Pattern Matching, as if the extglob shell option
       were enabled.  The = operator is equivalent to ==.  If the shell option
       nocasematch  is  enabled,  the match is performed without regard to the
       case of alphabetic characters.  The return value is  0  if  the  string
       matches  (==) or does not match (!=) the pattern, and 1 otherwise.  Any
       part of the pattern may be quoted to force the  quoted  portion  to  be
       matched as a string.

       An  additional  binary  operator,  =~,  is  available,  with  the  same
       precedence as == and !=.  When it is used, the string to the  right  of
       the  operator  is considered an extended regular expression and matched
       accordingly (as in regex(3)).  The return value  is  0  if  the  string
       matches  the  pattern,  and  1 otherwise.  If the regular expression is
       syntactically incorrect, the conditional expression's return  value  is
       2.   If the shell option nocasematch is enabled, the match is performed
       without regard to the case of alphabetic characters.  Any part  of  the
       pattern  may  be  quoted to force the quoted portion to be matched as a
       string.  Bracket expressions in regular  expressions  must  be  treated
       carefully,  since normal quoting characters lose their meanings between
       brackets.  If the pattern is stored in a shell  variable,  quoting  the
       variable expansion forces the entire pattern to be matched as a string.
       Substrings matched by parenthesized subexpressions within  the  regular
       expression  are  saved in the array variable BASH_REMATCH.  The element
       of BASH_REMATCH with index 0 is the portion of the string matching  the
       entire regular expression.  The element of BASH_REMATCH with index n is
       the portion of the string matching the nth parenthesized subexpression.

       Expressions may be combined using the following  operators,  listed  in
       decreasing order of precedence:

              ( expression )
                     Returns  the  value  of  expression.  This may be used to
                     override the normal precedence of operators.
              ! expression
                     True if expression is false.
              expression1 && expression2
                     True if both expression1 and expression2 are true.
              expression1 || expression2
                     True if either expression1 or expression2 is true.

              The && and || operators do not evaluate expression2 if the value
              of  expression1  is  sufficient to determine the return value of
              the entire conditional expression.

       for name [ [ in [ word ... ] ] ; ] do list ; done
              The list of words following in is expanded, generating a list of
              items.  The variable name is set to each element of this list in
              turn, and list is  executed  each  time.   If  the  in  word  is
              omitted,  the for command executes list once for each positional
              parameter that is set (see PARAMETERS below).  The return status
              is  the  exit  status of the last command that executes.  If the
              expansion of the items following in results in an empty list, no
              commands are executed, and the return status is 0.

       for (( expr1 ; expr2 ; expr3 )) ; do list ; done
              First, the arithmetic expression expr1 is evaluated according to
              the rules described  below  under  ARITHMETIC  EVALUATION.   The
              arithmetic  expression  expr2 is then evaluated repeatedly until
              it evaluates to zero.  Each time expr2 evaluates to  a  non-zero
              value,  list  is executed and the arithmetic expression expr3 is
              evaluated.  If any expression is omitted, it behaves  as  if  it
              evaluates to 1.  The return value is the exit status of the last
              command in list that  is  executed,  or  false  if  any  of  the
              expressions is invalid.

       select name [ in word ] ; do list ; done
              The list of words following in is expanded, generating a list of
              items.  The set of expanded words is  printed  on  the  standard
              error,  each  preceded  by a number.  If the in word is omitted,
              the positional parameters are printed  (see  PARAMETERS  below).
              The  PS3  prompt  is  then  displayed  and  a line read from the
              standard input.  If the line consists of a number  corresponding
              to  one of the displayed words, then the value of name is set to
              that word.  If the line is  empty,  the  words  and  prompt  are
              displayed  again.   If  EOF is read, the command completes.  Any
              other value read causes name to be set to null.  The  line  read
              is saved in the variable REPLY.  The list is executed after each
              selection until a break command is executed.  The exit status of
              select  is the exit status of the last command executed in list,
              or zero if no commands were executed.

       case word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac
              A case command first expands word, and tries to match it against
              each  pattern  in  turn,  using  the  same matching rules as for
              pathname expansion (see Pathname Expansion below).  The word  is
              expanded   using   tilde   expansion,   parameter  and  variable
              expansion,  arithmetic   substitution,   command   substitution,
              process  substitution  and quote removal.  Each pattern examined
              is  expanded  using  tilde  expansion,  parameter  and  variable
              expansion,  arithmetic  substitution,  command substitution, and
              process  substitution.   If  the  shell  option  nocasematch  is
              enabled,  the  match  is performed without regard to the case of
              alphabetic characters.  When a match is found, the corresponding
              list  is  executed.   If  the ;; operator is used, no subsequent
              matches are attempted after the first pattern match.   Using  ;&
              in  place  of  ;;  causes  execution  to  continue with the list
              associated with the next set of patterns.  Using ;;& in place of
              ;;  causes  the  shell  to  test  the  next  pattern list in the
              statement,  if  any,  and  execute  any  associated  list  on  a
              successful  match.   The  exit  status  is  zero  if  no pattern
              matches.  Otherwise, it is the exit status of the  last  command
              executed in list.

       if list; then list; [ elif list; then list; ] ... [ else list; ] fi
              The  if  list is executed.  If its exit status is zero, the then
              list is executed.  Otherwise, each  elif  list  is  executed  in
              turn,  and  if  its  exit status is zero, the corresponding then
              list is executed and the command completes.  Otherwise, the else
              list  is  executed,  if  present.   The  exit status is the exit
              status of the last command executed, or  zero  if  no  condition
              tested true.

       while list-1; do list-2; done
       until list-1; do list-2; done
              The  while command continuously executes the list list-2 as long
              as the last command in the list list-1 returns an exit status of
              zero.   The  until  command  is  identical to the while command,
              except that the test is negated; list-2 is executed as  long  as
              the  last command in list-1 returns a non-zero exit status.  The
              exit status of the while and until commands is the  exit  status
              of  the  last  command  executed  in list-2, or zero if none was
              executed.

   Coprocesses
       A coprocess is a shell command preceded by the coproc reserved word.  A
       coprocess  is  executed asynchronously in a subshell, as if the command
       had been terminated with the & control operator, with  a  two-way  pipe
       established between the executing shell and the coprocess.

       The format for a coprocess is:

              coproc [NAME] command [redirections]

       This  creates  a  coprocess  named  NAME.  If NAME is not supplied, the
       default name is COPROC.  NAME must not be  supplied  if  command  is  a
       simple  command  (see above); otherwise, it is interpreted as the first
       word of the simple command.  When the coprocess is executed, the  shell
       creates  an array variable (see Arrays below) named NAME in the context
       of the executing shell.  The standard output of  command  is  connected
       via  a  pipe to a file descriptor in the executing shell, and that file
       descriptor is assigned to NAME[0].  The standard input  of  command  is
       connected  via  a pipe to a file descriptor in the executing shell, and
       that file descriptor is assigned to NAME[1].  This pipe is  established
       before  any  redirections  specified  by  the  command (see REDIRECTION
       below).  The file descriptors can be utilized  as  arguments  to  shell
       commands  and  redirections  using  standard word expansions.  The file
       descriptors are not available in subshells.   The  process  ID  of  the
       shell spawned to execute the coprocess is available as the value of the
       variable NAME_PID.  The wait builtin command may be used  to  wait  for
       the coprocess to terminate.

       Since  the  coprocess is created as an asynchronous command, the coproc
       command always returns success.  The return status of  a  coprocess  is
       the exit status of command.

   Shell Function Definitions
       A  shell function is an object that is called like a simple command and
       executes a compound command with a new set  of  positional  parameters.
       Shell functions are declared as follows:

       name () compound-command [redirection]
       function name [()] compound-command [redirection]
              This  defines a function named name.  The reserved word function
              is optional.  If the function reserved  word  is  supplied,  the
              parentheses  are  optional.   The  body  of  the function is the
              compound command compound-command (see Compound Commands above).
              That  command is usually a list of commands between { and }, but
              may  be  any  command  listed  under  Compound  Commands  above.
              compound-command  is  executed whenever name is specified as the
              name of a simple command.  When in posix mode, name may  not  be
              the name of one of the POSIX special builtins.  Any redirections
              (see REDIRECTION below) specified when a function is defined are
              performed  when  the function is executed.  The exit status of a
              function definition is zero unless a syntax error  occurs  or  a
              readonly  function  with  the  same  name  already exists.  When
              executed, the exit status of a function is the  exit  status  of
              the last command executed in the body.  (See FUNCTIONS below.)

COMMENTS

       In  a  non-interactive  shell,  or  an  interactive  shell in which the
       interactive_comments option to the shopt builtin is enabled (see  SHELL
       BUILTIN  COMMANDS  below), a word beginning with # causes that word and
       all remaining characters on that line to be  ignored.   An  interactive
       shell  without  the  interactive_comments option enabled does not allow
       comments.   The  interactive_comments  option  is  on  by  default   in
       interactive shells.

QUOTING

       Quoting  is used to remove the special meaning of certain characters or
       words to the shell.  Quoting can be used to disable  special  treatment
       for special characters, to prevent reserved words from being recognized
       as such, and to prevent parameter expansion.

       Each of the metacharacters listed above under DEFINITIONS  has  special
       meaning to the shell and must be quoted if it is to represent itself.

       When  the  command  history  expansion  facilities  are being used (see
       HISTORY EXPANSION below), the history expansion character,  usually  !,
       must be quoted to prevent history expansion.

       There  are  three  quoting  mechanisms:  the  escape  character, single
       quotes, and double quotes.

       A non-quoted backslash (\) is the escape character.  It  preserves  the
       literal value of the next character that follows, with the exception of
       <newline>.  If a \<newline> pair appears,  and  the  backslash  is  not
       itself  quoted,  the \<newline> is treated as a line continuation (that
       is, it is removed from the input stream and effectively ignored).

       Enclosing characters in single quotes preserves the  literal  value  of
       each character within the quotes.  A single quote may not occur between
       single quotes, even when preceded by a backslash.

       Enclosing characters in double quotes preserves the  literal  value  of
       all  characters  within the quotes, with the exception of $, `, \, and,
       when history expansion is enabled, !.  The characters $  and  `  retain
       their  special meaning within double quotes.  The backslash retains its
       special meaning only when followed by one of the following  characters:
       $,  `,  ", \, or <newline>.  A double quote may be quoted within double
       quotes by preceding it with a backslash.  If enabled, history expansion
       will  be  performed  unless an !  appearing in double quotes is escaped
       using a backslash.  The backslash preceding the !  is not removed.

       The special parameters * and @ have  special  meaning  when  in  double
       quotes (see PARAMETERS below).

       Words of the form $'string' are treated specially.  The word expands to
       string, with backslash-escaped characters replaced as specified by  the
       ANSI  C  standard.  Backslash escape sequences, if present, are decoded
       as follows:
              \a     alert (bell)
              \b     backspace
              
              \E     an escape character
                   form feed
              
     new line
              
     carriage return
              	     horizontal tab
                   vertical tab
              \     backslash
              \'     single quote
              \"     double quote
              \nnn   the eight-bit character whose value is  the  octal  value
                     nnn (one to three 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)
              \cx    a control-x character

       The expanded result is single-quoted, as if the  dollar  sign  had  not
       been present.

       A double-quoted string preceded by a dollar sign ($"string") will cause
       the string to be translated according to the current  locale.   If  the
       current  locale  is  C  or  POSIX,  the dollar sign is ignored.  If the
       string is translated and replaced, the replacement is double-quoted.

PARAMETERS

       A parameter is an entity that stores values.   It  can  be  a  name,  a
       number,  or  one  of  the special characters listed below under Special
       Parameters.  A variable is a parameter denoted by a name.   A  variable
       has a value and zero or more attributes.  Attributes are assigned using
       the declare  builtin  command  (see  declare  below  in  SHELL  BUILTIN
       COMMANDS).

       A parameter is set if it has been assigned a value.  The null string is
       a valid value.  Once a variable is set, it may be unset only  by  using
       the unset builtin command (see SHELL BUILTIN COMMANDS below).

       A variable may be assigned to by a statement of the form

              name=[value]

       If  value  is not given, the variable is assigned the null string.  All
       values undergo  tilde  expansion,  parameter  and  variable  expansion,
       command  substitution,  arithmetic  expansion,  and  quote removal (see
       EXPANSION below).  If the variable has its integer attribute set,  then
       value  is  evaluated  as  an arithmetic expression even if the $((...))
       expansion is not used (see Arithmetic Expansion below).  Word splitting
       is  not  performed, with the exception of "$@" as explained below under
       Special Parameters.  Pathname expansion is not  performed.   Assignment
       statements may also appear as arguments to the alias, declare, typeset,
       export, readonly, and local builtin  commands.   When  in  posix  mode,
       these  builtins  may appear in a command after one or more instances of
       the command builtin and retain these assignment statement properties.

       In the context where an assignment statement is assigning a value to  a
       shell variable or array index, the += operator can be used to append to
       or add to the variable's previous value.   When  +=  is  applied  to  a
       variable  for  which  the  integer  attribute  has  been  set, value is
       evaluated as an arithmetic  expression  and  added  to  the  variable's
       current value, which is also evaluated.  When += is applied to an array
       variable using compound assignment (see Arrays below),  the  variable's
       value is not unset (as it is when using =), and new values are appended
       to the array beginning at one greater than the  array's  maximum  index
       (for  indexed  arrays)  or  added  as  additional key-value pairs in an
       associative array.  When applied to a string-valued variable, value  is
       expanded and appended to the variable's value.

       A variable can be assigned the nameref attribute using the -n option to
       the declare or local builtin commands (see the descriptions of  declare
       and  local  below)  to  create  a  nameref,  or  a reference to another
       variable.   This  allows  variables  to  be   manipulated   indirectly.
       Whenever  the  nameref  variable  is  referenced  or  assigned  to, the
       operation is actually  performed  on  the  variable  specified  by  the
       nameref  variable's  value.   A  nameref  is commonly used within shell
       functions to refer to a variable whose name is passed as an argument to
       the  function.   For  instance, if a variable name is passed to a shell
       function as its first argument, running
              declare -n ref=$1
       inside the function creates a nameref variable ref whose value  is  the
       variable name passed as the first argument.  References and assignments
       to ref are treated as references and assignments to the variable  whose
       name  was  passed as $1.  If the control variable in a for loop has the
       nameref attribute, the list of words can be a list of shell  variables,
       and  a name reference will be established for each word in the list, in
       turn, when the loop is executed.  Array variables cannot be  given  the
       -n attribute.  However, nameref variables can reference array variables
       and subscripted array variables.  Namerefs can be unset  using  the  -n
       option  to the unset builtin.  Otherwise, if unset is executed with the
       name of a nameref variable as an argument, the variable  referenced  by
       the nameref variable will be unset.

   Positional Parameters
       A  positional  parameter  is a parameter denoted by one or more digits,
       other than the single digit 0.  Positional parameters are assigned from
       the  shell's  arguments when it is invoked, and may be reassigned using
       the set builtin command.  Positional parameters may not be assigned  to
       with  assignment statements.  The positional parameters are temporarily
       replaced when a shell function is executed (see FUNCTIONS below).

       When a positional parameter consisting of more than a single  digit  is
       expanded, it must be enclosed in braces (see EXPANSION below).

   Special Parameters
       The  shell  treats  several parameters specially.  These parameters may
       only be referenced; assignment to them is not allowed.
       *      Expands to the positional parameters, starting from  one.   When
              the  expansion  is  not  within  double  quotes, each positional
              parameter expands to a separate word.  In contexts where  it  is
              performed, those words are subject to further word splitting and
              pathname expansion.  When the  expansion  occurs  within  double
              quotes,  it  expands  to  a  single  word with the value of each
              parameter separated by the first character of  the  IFS  special
              variable.   That  is, "$*" is equivalent to "$1c$2c...", where c
              is the first character of the value of the IFS variable.  If IFS
              is  unset,  the  parameters  are separated by spaces.  If IFS is
              null, the parameters are joined without intervening separators.
       @      Expands to the positional parameters, starting from  one.   When
              the  expansion  occurs  within  double  quotes,  each  parameter
              expands to a separate word.  That is, "$@" is equivalent to "$1"
              "$2"  ...   If the double-quoted expansion occurs within a word,
              the  expansion  of  the  first  parameter  is  joined  with  the
              beginning  part  of  the original word, and the expansion of the
              last parameter is joined with the  last  part  of  the  original
              word.   When  there  are  no  positional parameters, "$@" and $@
              expand to nothing (i.e., they are removed).
       #      Expands to the number of positional parameters in decimal.
       ?      Expands to  the  exit  status  of  the  most  recently  executed
              foreground pipeline.
       -      Expands   to   the   current  option  flags  as  specified  upon
              invocation, by the set builtin command,  or  those  set  by  the
              shell itself (such as the -i option).
       $      Expands  to  the  process ID of the shell.  In a () subshell, it
              expands to  the  process  ID  of  the  current  shell,  not  the
              subshell.
       !      Expands  to  the process ID of the job most recently placed into
              the background, whether executed as an asynchronous  command  or
              using the bg builtin (see JOB CONTROL below).
       0      Expands  to  the name of the shell or shell script.  This is set
              at shell initialization.  If bash is  invoked  with  a  file  of
              commands,  $0  is  set  to  the  name  of that file.  If bash is
              started with the -c option, then $0 is set to the first argument
              after  the string to be executed, if one is present.  Otherwise,
              it is set to the filename used  to  invoke  bash,  as  given  by
              argument zero.
       _      At  shell  startup,  set to the absolute pathname used to invoke
              the shell or shell  script  being  executed  as  passed  in  the
              environment or argument list.  Subsequently, expands to the last
              argument to the previous command, after expansion.  Also set  to
              the  full  pathname  used  to  invoke  each command executed and
              placed in  the  environment  exported  to  that  command.   When
              checking  mail,  this  parameter holds the name of the mail file
              currently being checked.

   Shell Variables
       The following variables are set by the shell:

       BASH   Expands to the full filename used to  invoke  this  instance  of
              bash.
       BASHOPTS
              A  colon-separated  list of enabled shell options.  Each word in
              the list is a valid argument for the  -s  option  to  the  shopt
              builtin command (see SHELL BUILTIN COMMANDS below).  The options
              appearing in BASHOPTS are those reported as  on  by  shopt.   If
              this  variable  is  in the environment when bash starts up, each
              shell option in the list will  be  enabled  before  reading  any
              startup files.  This variable is read-only.
       BASHPID
              Expands  to  the  process  ID of the current bash process.  This
              differs from $$ under certain circumstances, such  as  subshells
              that do not require bash to be re-initialized.
       BASH_ALIASES
              An  associative  array  variable whose members correspond to the
              internal list of aliases as maintained  by  the  alias  builtin.
              Elements added to this array appear in the alias list; unsetting
              array elements cause aliases to be removed from the alias list.
       BASH_ARGC
              An array variable whose values are the number of  parameters  in
              each frame of the current bash execution call stack.  The number
              of parameters to  the  current  subroutine  (shell  function  or
              script  executed  with  . or source) is at the top of the stack.
              When a subroutine is executed, the number of  parameters  passed
              is pushed onto BASH_ARGC.  The shell sets BASH_ARGC only when in
              extended debugging mode (see the  description  of  the  extdebug
              option to the shopt builtin below)
       BASH_ARGV
              An  array  variable  containing  all  of  the  parameters in the
              current bash execution call stack.  The final parameter  of  the
              last  subroutine  call  is  at  the  top of the stack; the first
              parameter of  the  initial  call  is  at  the  bottom.   When  a
              subroutine  is executed, the parameters supplied are pushed onto
              BASH_ARGV.  The shell  sets  BASH_ARGV  only  when  in  extended
              debugging  mode  (see  the description of the extdebug option to
              the shopt builtin below)
       BASH_CMDS
              An associative array variable whose members  correspond  to  the
              internal  hash  table  of  commands  as  maintained  by the hash
              builtin.  Elements added to this array appear in the hash table;
              unsetting  array  elements cause commands to be removed from the
              hash table.
       BASH_COMMAND
              The command currently being executed or about  to  be  executed,
              unless the shell is executing a command as the result of a trap,
              in which case it is the command executing at  the  time  of  the
              trap.
       BASH_EXECUTION_STRING
              The command argument to the -c invocation option.
       BASH_LINENO
              An  array  variable whose members are the line numbers in source
              files where each corresponding member of FUNCNAME  was  invoked.
              ${BASH_LINENO[$i]}  is  the  line  number  in  the  source  file
              (${BASH_SOURCE[$i+1]})  where  ${FUNCNAME[$i]}  was  called  (or
              ${BASH_LINENO[$i-1]}   if   referenced   within   another  shell
              function).  Use LINENO to obtain the current line number.
       BASH_REMATCH
              An array variable whose members are assigned by  the  =~  binary
              operator  to the [[ conditional command.  The element with index
              0 is the portion of  the  string  matching  the  entire  regular
              expression.   The  element  with  index  n is the portion of the
              string  matching  the  nth  parenthesized  subexpression.   This
              variable is read-only.
       BASH_SOURCE
              An  array  variable whose members are the source filenames where
              the corresponding shell function names  in  the  FUNCNAME  array
              variable  are  defined.   The  shell function ${FUNCNAME[$i]} is
              defined  in  the  file  ${BASH_SOURCE[$i]}   and   called   from
              ${BASH_SOURCE[$i+1]}.
       BASH_SUBSHELL
              Incremented  by one within each subshell or subshell environment
              when the  shell  begins  executing  in  that  environment.   The
              initial value is 0.
       BASH_VERSINFO
              A readonly array variable whose members hold version information
              for this instance of bash.  The values  assigned  to  the  array
              members are as follows:
              BASH_VERSINFO[0]        The major version number (the release).
              BASH_VERSINFO[1]        The minor version number (the version).
              BASH_VERSINFO[2]        The patch level.
              BASH_VERSINFO[3]        The build version.
              BASH_VERSINFO[4]        The release status (e.g., beta1).
              BASH_VERSINFO[5]        The value of MACHTYPE.
       BASH_VERSION
              Expands  to  a string describing the version of this instance of
              bash.
       COMP_CWORD
              An index into ${COMP_WORDS} of the word containing  the  current
              cursor  position.   This  variable  is  available  only in shell
              functions invoked by the programmable completion facilities (see
              Programmable Completion below).
       COMP_KEY
              The  key  (or  final  key  of a key sequence) used to invoke the
              current completion function.
       COMP_LINE
              The current command line.  This variable is  available  only  in
              shell   functions   and   external   commands   invoked  by  the
              programmable completion facilities (see Programmable  Completion
              below).
       COMP_POINT
              The  index  of  the  current  cursor  position  relative  to the
              beginning  of  the  current  command.   If  the  current  cursor
              position is at the end of the current command, the value of this
              variable is equal to ${#COMP_LINE}.  This variable is  available
              only  in  shell  functions  and external commands invoked by the
              programmable completion facilities (see Programmable  Completion
              below).
       COMP_TYPE
              Set  to an integer value corresponding to the type of completion
              attempted that caused a completion function to be  called:  TAB,
              for   normal   completion,  ?,  for  listing  completions  after
              successive tabs, !, for listing  alternatives  on  partial  word
              completion,   @,   to  list  completions  if  the  word  is  not
              unmodified,  or  %,  for  menu  completion.   This  variable  is
              available  only in shell functions and external commands invoked
              by the  programmable  completion  facilities  (see  Programmable
              Completion below).
       COMP_WORDBREAKS
              The  set  of characters that the readline library treats as word
              separators when performing word completion.  If  COMP_WORDBREAKS
              is  unset,  it  loses  its  special  properties,  even  if it is
              subsequently reset.
       COMP_WORDS
              An  array  variable  (see  Arrays  below)  consisting   of   the
              individual words in the current command line.  The line is split
              into words as readline would split it, using COMP_WORDBREAKS  as
              described  above.   This  variable  is  available  only in shell
              functions invoked by the programmable completion facilities (see
              Programmable Completion below).
       COPROC An  array  variable  (see Arrays below) created to hold the file
              descriptors for output from and input to  an  unnamed  coprocess
              (see Coprocesses above).
       DIRSTACK
              An  array  variable  (see  Arrays  below) containing the current
              contents of the directory  stack.   Directories  appear  in  the
              stack  in  the  order  they  are  displayed by the dirs builtin.
              Assigning to members of this  array  variable  may  be  used  to
              modify  directories already in the stack, but the pushd and popd
              builtins must be used to add and remove directories.  Assignment
              to  this  variable  will  not  change the current directory.  If
              DIRSTACK is unset, it loses its special properties, even  if  it
              is subsequently reset.
       EUID   Expands   to   the  effective  user  ID  of  the  current  user,
              initialized at shell startup.  This variable is readonly.
       FUNCNAME
              An array variable containing the names of  all  shell  functions
              currently in the execution call stack.  The element with index 0
              is the name of  any  currently-executing  shell  function.   The
              bottom-most  element (the one with the highest index) is "main".
              This variable exists only when a shell  function  is  executing.
              Assignments  to  FUNCNAME  have  no  effect  and return an error
              status.  If FUNCNAME is unset, it loses its special  properties,
              even if it is subsequently reset.

              This  variable  can  be  used  with BASH_LINENO and BASH_SOURCE.
              Each  element  of  FUNCNAME  has   corresponding   elements   in
              BASH_LINENO  and  BASH_SOURCE  to  describe the call stack.  For
              instance,   ${FUNCNAME[$i]}   was   called   from    the    file
              ${BASH_SOURCE[$i+1]}  at  line  number  ${BASH_LINENO[$i]}.  The
              caller builtin  displays  the  current  call  stack  using  this
              information.
       GROUPS An  array  variable  containing  the list of groups of which the
              current user is a member.  Assignments to GROUPS have no  effect
              and  return  an  error status.  If GROUPS is unset, it loses its
              special properties, even if it is subsequently reset.
       HISTCMD
              The history number, or index in the history list, of the current
              command.   If HISTCMD is unset, it loses its special properties,
              even if it is subsequently reset.
       HOSTNAME
              Automatically set to the name of the current host.
       HOSTTYPE
              Automatically set to a string that uniquely describes  the  type
              of  machine  on which bash is executing.  The default is system-
              dependent.
       LINENO Each time this parameter is referenced, the shell substitutes  a
              decimal  number  representing the current sequential line number
              (starting with 1) within a script or function.  When  not  in  a
              script  or  function, the value substituted is not guaranteed to
              be meaningful.   If  LINENO  is  unset,  it  loses  its  special
              properties, even if it is subsequently reset.
       MACHTYPE
              Automatically  set  to  a string that fully describes the system
              type on which bash  is  executing,  in  the  standard  GNU  cpu-
              company-system format.  The default is system-dependent.
       MAPFILE
              An  array  variable  (see Arrays below) created to hold the text
              read by the mapfile builtin when no variable name is supplied.
       OLDPWD The previous working directory as set by the cd command.
       OPTARG The value of the last option argument processed by  the  getopts
              builtin command (see SHELL BUILTIN COMMANDS below).
       OPTIND The  index  of  the next argument to be processed by the getopts
              builtin command (see SHELL BUILTIN COMMANDS below).
       OSTYPE Automatically set to  a  string  that  describes  the  operating
              system  on  which  bash  is  executing.   The default is system-
              dependent.
       PIPESTATUS
              An array variable (see Arrays below) containing a list  of  exit
              status  values  from the processes in the most-recently-executed
              foreground pipeline (which may contain only a single command).
       PPID   The  process  ID  of  the  shell's  parent.   This  variable  is
              readonly.
       PWD    The current working directory as set by the cd command.
       RANDOM Each time this parameter is referenced, a random integer between
              0 and 32767 is generated.  The sequence of random numbers may be
              initialized by assigning a value to RANDOM.  If RANDOM is unset,
              it loses its special properties,  even  if  it  is  subsequently
              reset.
       READLINE_LINE
              The contents of the readline line buffer, for use with "bind -x"
              (see SHELL BUILTIN COMMANDS below).
       READLINE_POINT
              The position of the insertion point in the readline line buffer,
              for use with "bind -x" (see SHELL BUILTIN COMMANDS below).
       REPLY  Set  to  the line of input read by the read builtin command when
              no arguments are supplied.
       SECONDS
              Each time this parameter is referenced, the  number  of  seconds
              since  shell  invocation is returned.  If a value is assigned to
              SECONDS, the value returned upon subsequent  references  is  the
              number  of seconds since the assignment plus the value assigned.
              If SECONDS is unset, it loses its special properties, even if it
              is subsequently reset.
       SHELLOPTS
              A  colon-separated  list of enabled shell options.  Each word in
              the list is a valid argument  for  the  -o  option  to  the  set
              builtin command (see SHELL BUILTIN COMMANDS below).  The options
              appearing in SHELLOPTS are those reported as on by set  -o.   If
              this  variable  is  in the environment when bash starts up, each
              shell option in the list will  be  enabled  before  reading  any
              startup files.  This variable is read-only.
       SHLVL  Incremented by one each time an instance of bash is started.
       UID    Expands to the user ID of the current user, initialized at shell
              startup.  This variable is readonly.

       The following variables are used by the shell.   In  some  cases,  bash
       assigns a default value to a variable; these cases are noted below.

       BASH_COMPAT
              The  value  is used to set the shell's compatibility level.  See
              the description of the shopt builtin below under  SHELL  BUILTIN
              COMMANDS  for  a description of the various compatibility levels
              and their effects.  The value may be  a  decimal  number  (e.g.,
              4.2)  or  an  integer  (e.g.,  42)  corresponding to the desired
              compatibility level.  If BASH_COMPAT is  unset  or  set  to  the
              empty  string, the compatibility level is set to the default for
              the current version.  If BASH_COMPAT is set to a value  that  is
              not  one  of the valid compatibility levels, the shell prints an
              error message and sets the compatibility level  to  the  default
              for   the  current  version.   The  valid  compatibility  levels
              correspond to the compatibility options accepted  by  the  shopt
              builtin  described  below  (for example, compat42 means that 4.2
              and 42 are valid values).  The current version is also  a  valid
              value.
       BASH_ENV
              If  this parameter is set when bash is executing a shell script,
              its value is interpreted as a filename  containing  commands  to
              initialize the shell, as in ~/.bashrc.  The value of BASH_ENV is
              subjected to  parameter  expansion,  command  substitution,  and
              arithmetic  expansion  before  being  interpreted as a filename.
              PATH is not used to search for the resultant filename.
       BASH_XTRACEFD
              If set to an integer corresponding to a valid  file  descriptor,
              bash  will  write  the  trace  output  generated  when set -x is
              enabled to that file descriptor.  The file descriptor is  closed
              when  BASH_XTRACEFD is unset or assigned a new value.  Unsetting
              BASH_XTRACEFD or assigning it the empty string causes the  trace
              output  to  be  sent  to  the standard error.  Note that setting
              BASH_XTRACEFD to 2 (the standard error file descriptor) and then
              unsetting it will result in the standard error being closed.
       CDPATH The  search  path for the cd command.  This is a colon-separated
              list of directories in which the  shell  looks  for  destination
              directories  specified  by  the  cd  command.  A sample value is
              ".:~:/usr".
       CHILD_MAX
              Set the number of exited child status values for  the  shell  to
              remember.   Bash will not allow this value to be decreased below
              a  POSIX-mandated  minimum,  and  there  is  a   maximum   value
              (currently 8192) that this may not exceed.  The minimum value is
              system-dependent.
       COLUMNS
              Used by the select compound command to  determine  the  terminal
              width  when  printing selection lists.  Automatically set if the
              checkwinsize option is enabled or in an interactive  shell  upon
              receipt of a SIGWINCH.
       COMPREPLY
              An array variable from which bash reads the possible completions
              generated by  a  shell  function  invoked  by  the  programmable
              completion  facility  (see Programmable Completion below).  Each
              array element contains one possible completion.
       EMACS  If bash finds this variable in the environment  when  the  shell
              starts  with  value "t", it assumes that the shell is running in
              an Emacs shell buffer and disables line editing.
       ENV    Similar to BASH_ENV; used when the shell  is  invoked  in  POSIX
              mode.
       FCEDIT The default editor for the fc builtin command.
       FIGNORE
              A  colon-separated  list  of  suffixes to ignore when performing
              filename completion (see  READLINE  below).   A  filename  whose
              suffix  matches  one  of the entries in FIGNORE is excluded from
              the list  of  matched  filenames.   A  sample  value  is  ".o:~"
              (Quoting  is  needed  when  assigning  a value to this variable,
              which contains tildes).
       FUNCNEST
              If set to a numeric value greater  than  0,  defines  a  maximum
              function  nesting  level.  Function invocations that exceed this
              nesting level will cause the current command to abort.
       GLOBIGNORE
              A colon-separated list of patterns defining the set of filenames
              to be ignored by pathname expansion.  If a filename matched by a
              pathname expansion pattern also matches one of the  patterns  in
              GLOBIGNORE, it is removed from the list of matches.
       HISTCONTROL
              A  colon-separated  list  of values controlling how commands are
              saved on the history list.   If  the  list  of  values  includes
              ignorespace,  lines  which  begin with a space character are not
              saved in the history list.  A value of ignoredups  causes  lines
              matching the previous history entry to not be saved.  A value of
              ignoreboth is shorthand for ignorespace and ignoredups.  A value
              of erasedups causes all previous lines matching the current line
              to be removed from the history list before that line  is  saved.
              Any  value  not in the above list is ignored.  If HISTCONTROL is
              unset, or does not include a valid value, all lines read by  the
              shell parser are saved on the history list, subject to the value
              of HISTIGNORE.  The second and subsequent lines of a  multi-line
              compound  command  are  not tested, and are added to the history
              regardless of the value of HISTCONTROL.
       HISTFILE
              The name of the file in which  command  history  is  saved  (see
              HISTORY  below).   The  default  value  is  ~/.bash_history.  If
              unset, the command history is not saved when a shell exits.
       HISTFILESIZE
              The maximum number of lines contained in the history file.  When
              this   variable  is  assigned  a  value,  the  history  file  is
              truncated, if necessary, to contain no more than that number  of
              lines  by removing the oldest entries.  The history file is also
              truncated to this size after writing it when a shell exits.   If
              the  value  is  0,  the  history file is truncated to zero size.
              Non-numeric values and numeric values  less  than  zero  inhibit
              truncation.   The  shell  sets the default value to the value of
              HISTSIZE after reading any startup files.
       HISTIGNORE
              A colon-separated list of patterns used to decide which  command
              lines  should  be  saved  on  the history list.  Each pattern is
              anchored at the  beginning  of  the  line  and  must  match  the
              complete  line  (no  implicit `*' is appended).  Each pattern is
              tested  against  the  line  after  the   checks   specified   by
              HISTCONTROL  are  applied.   In  addition  to  the  normal shell
              pattern matching characters, `&' matches  the  previous  history
              line.   `&'  may  be escaped using a backslash; the backslash is
              removed before attempting a match.  The  second  and  subsequent
              lines  of  a multi-line compound command are not tested, and are
              added to the history regardless of the value of HISTIGNORE.
       HISTSIZE
              The number of commands to remember in the command  history  (see
              HISTORY  below).   If  the value is 0, commands are not saved in
              the history list.  Numeric values less than zero result in every
              command  being  saved  on  the history list (there is no limit).
              The shell sets the  default  value  to  500  after  reading  any
              startup files.
       HISTTIMEFORMAT
              If  this  variable  is  set and not null, its value is used as a
              format string for strftime(3) to print the time stamp associated
              with  each  history  entry displayed by the history builtin.  If
              this variable is set, time stamps are  written  to  the  history
              file  so they may be preserved across shell sessions.  This uses
              the history comment character  to  distinguish  timestamps  from
              other history lines.
       HOME   The home directory of the current user; the default argument for
              the cd builtin command.  The value of this variable is also used
              when performing tilde expansion.
       HOSTFILE
              Contains  the  name  of  a file in the same format as /etc/hosts
              that should be read when the shell needs to complete a hostname.
              The  list  of possible hostname completions may be changed while
              the shell is running;  the  next  time  hostname  completion  is
              attempted  after the value is changed, bash adds the contents of
              the new file to the existing list.  If HOSTFILE is set, but  has
              no  value,  or  does  not name a readable file, bash attempts to
              read  /etc/hosts  to  obtain  the  list  of  possible   hostname
              completions.   When  HOSTFILE  is  unset,  the  hostname list is
              cleared.
       IFS    The Internal Field Separator that is  used  for  word  splitting
              after  expansion  and  to  split  lines into words with the read
              builtin      command.       The      default      value       is
              ``<space><tab><newline>''.
       IGNOREEOF
              Controls the action of an interactive shell on receipt of an EOF
              character as the sole input.  If set, the value is the number of
              consecutive  EOF  characters  which  must  be typed as the first
              characters on an input line before bash exits.  If the  variable
              exists  but  does not have a numeric value, or has no value, the
              default value is 10.  If it does not exist,  EOF  signifies  the
              end of input to the shell.
       INPUTRC
              The  filename  for  the  readline  startup  file, overriding the
              default of ~/.inputrc (see READLINE below).
       LANG   Used to determine the  locale  category  for  any  category  not
              specifically selected with a variable starting with LC_.
       LC_ALL This  variable  overrides  the  value  of LANG and any other LC_
              variable specifying a locale category.
       LC_COLLATE
              This variable determines the collation order used  when  sorting
              the  results  of pathname expansion, and determines the behavior
              of  range  expressions,  equivalence  classes,   and   collating
              sequences within pathname expansion and pattern matching.
       LC_CTYPE
              This  variable  determines  the interpretation of characters and
              the behavior of character classes within pathname expansion  and
              pattern matching.
       LC_MESSAGES
              This  variable  determines  the locale used to translate double-
              quoted strings preceded by a $.
       LC_NUMERIC
              This variable determines the locale  category  used  for  number
              formatting.
       LINES  Used  by  the  select  compound  command to determine the column
              length for printing selection lists.  Automatically set  if  the
              checkwinsize  option  is enabled or in an interactive shell upon
              receipt of a SIGWINCH.
       MAIL   If this parameter is set to a file or  directory  name  and  the
              MAILPATH  variable  is  not  set,  bash  informs the user of the
              arrival  of  mail  in  the  specified  file  or   Maildir-format
              directory.
       MAILCHECK
              Specifies  how  often  (in  seconds)  bash checks for mail.  The
              default is 60 seconds.  When it is time to check for  mail,  the
              shell  does  so  before  displaying the primary prompt.  If this
              variable is unset, or set to  a  value  that  is  not  a  number
              greater than or equal to zero, the shell disables mail checking.
       MAILPATH
              A colon-separated list of filenames to be checked for mail.  The
              message to be printed when mail arrives in a particular file may
              be  specified by separating the filename from the message with a
              `?'.  When used in the text of the message, $_  expands  to  the
              name of the current mailfile.  Example:
              MAILPATH='/var/mail/bfox?"You  have  mail":~/shell-mail?"$_  has
              mail!"'
              Bash supplies  a  default  value  for  this  variable,  but  the
              location of the user mail files that it uses is system dependent
              (e.g., /var/mail/$USER).
       OPTERR If set to the value 1, bash displays error messages generated by
              the  getopts builtin command (see SHELL BUILTIN COMMANDS below).
              OPTERR is initialized to 1 each time the shell is invoked  or  a
              shell script is executed.
       PATH   The  search  path for commands.  It is a colon-separated list of
              directories in which the shell looks for commands  (see  COMMAND
              EXECUTION  below).   A  zero-length (null) directory name in the
              value of PATH indicates the current directory.  A null directory
              name  may  appear  as  two  adjacent colons, or as an initial or
              trailing colon.  The default path is  system-dependent,  and  is
              set  by  the administrator who installs bash.  A common value is
              ``/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
       POSIXLY_CORRECT
              If  this  variable  is  in the environment when bash starts, the
              shell enters posix mode before reading the startup files, as  if
              the  --posix  invocation option had been supplied.  If it is set
              while the shell is running, bash enables posix mode, as  if  the
              command set -o posix had been executed.
       PROMPT_COMMAND
              If set, the value is executed as a command prior to issuing each
              primary prompt.
       PROMPT_DIRTRIM
              If set to a number greater than zero, the value is used  as  the
              number of trailing directory components to retain when expanding
              the \w and \W  prompt  string  escapes  (see  PROMPTING  below).
              Characters removed are replaced with an ellipsis.
       PS1    The  value  of  this parameter is expanded (see PROMPTING below)
              and used as the primary prompt string.   The  default  value  is
              ``\s-\$ ''.
       PS2    The  value of this parameter is expanded as with PS1 and used as
              the secondary prompt string.  The default is ``> ''.
       PS3    The value of this parameter is used as the prompt for the select
              command (see SHELL GRAMMAR above).
       PS4    The  value  of  this  parameter  is expanded as with PS1 and the
              value is printed before each command  bash  displays  during  an
              execution  trace.   The  first  character  of  PS4 is replicated
              multiple times, as necessary, to  indicate  multiple  levels  of
              indirection.  The default is ``+ ''.
       SHELL  The  full  pathname  to  the  shell  is kept in this environment
              variable.  If it is not set when the shell starts, bash  assigns
              to it the full pathname of the current user's login shell.
       TIMEFORMAT
              The  value  of  this  parameter  is  used  as  a  format  string
              specifying how the timing  information  for  pipelines  prefixed
              with  the  time  reserved  word  should  be  displayed.   The  %
              character introduces an escape sequence that is  expanded  to  a
              time value or other information.  The escape sequences and their
              meanings are as follows; the braces denote optional portions.
              %%        A literal %.
              %[p][l]R  The elapsed time in seconds.
              %[p][l]U  The number of CPU seconds spent in user mode.
              %[p][l]S  The number of CPU seconds spent in system mode.
              %P        The CPU percentage, computed as (%U + %S) / %R.

              The optional p is a digit specifying the precision,  the  number
              of fractional digits after a decimal point.  A value of 0 causes
              no decimal point or fraction to be output.  At most three places
              after  the  decimal  point may be specified; values of p greater
              than 3 are changed to 3.  If p is not specified, the value 3  is
              used.

              The  optional l specifies a longer format, including minutes, of
              the form MMmSS.FFs.  The value of p determines  whether  or  not
              the fraction is included.

              If  this  variable  is not set, bash acts as if it had the value
              $'
real	%3lR
user	%3lU
sys	%3lS'.  If the value  is  null,
              no timing information is displayed.  A trailing newline is added
              when the format string is displayed.
       TMOUT  If set to a value greater than zero, TMOUT  is  treated  as  the
              default  timeout  for  the  read  builtin.   The  select command
              terminates if input does not arrive  after  TMOUT  seconds  when
              input  is  coming from a terminal.  In an interactive shell, the
              value is interpreted as the number of seconds to wait for a line
              of  input  after  issuing  the  primary prompt.  Bash terminates
              after waiting for that number of seconds if a complete  line  of
              input does not arrive.
       TMPDIR If  set, bash uses its value as the name of a directory in which
              bash creates temporary files for the shell's use.
       auto_resume
              This variable controls how the shell interacts with the user and
              job  control.   If  this  variable  is  set,  single word simple
              commands without redirections  are  treated  as  candidates  for
              resumption  of  an  existing stopped job.  There is no ambiguity
              allowed; if there is more than one job beginning with the string
              typed,  the job most recently accessed is selected.  The name of
              a stopped job, in this context, is  the  command  line  used  to
              start  it.   If set to the value exact, the string supplied must
              match the name of a stopped job exactly; if  set  to  substring,
              the  string supplied needs to match a substring of the name of a
              stopped  job.   The  substring  value   provides   functionality
              analogous to the %?  job identifier (see JOB CONTROL below).  If
              set to any other value, the supplied string must be a prefix  of
              a  stopped  job's name; this provides functionality analogous to
              the %string job identifier.
       histchars
              The two or three characters which control history expansion  and
              tokenization (see HISTORY EXPANSION below).  The first character
              is the history expansion character, the character which  signals
              the  start  of  a  history  expansion, normally `!'.  The second
              character is the quick substitution character, which is used  as
              shorthand   for   re-running   the   previous  command  entered,
              substituting one string for another in the command.  The default
              is  `^'.   The  optional  third character is the character which
              indicates that the remainder of the line is a comment when found
              as  the  first  character  of a word, normally `#'.  The history
              comment character causes history substitution to be skipped  for
              the  remaining words on the line.  It does not necessarily cause
              the shell parser to treat the rest of the line as a comment.

   Arrays
       Bash provides one-dimensional indexed and associative array  variables.
       Any  variable may be used as an indexed array; the declare builtin will
       explicitly declare an array.  There is no maximum limit on the size  of
       an  array,  nor  any  requirement  that  members be indexed or assigned
       contiguously.  Indexed arrays are referenced using integers  (including
       arithmetic  expressions)   and  are  zero-based; associative arrays are
       referenced using arbitrary strings.  Unless  otherwise  noted,  indexed
       array indices must be non-negative integers.

       An  indexed  array is created automatically if any variable is assigned
       to using the syntax name[subscript]=value.  The subscript is treated as
       an arithmetic expression that must evaluate to a number.  To explicitly
       declare an indexed array,  use  declare  -a  name  (see  SHELL  BUILTIN
       COMMANDS  below).   declare  -a  name[subscript]  is also accepted; the
       subscript is ignored.

       Associative arrays are created using declare -A name.

       Attributes may be specified for an array variable using the declare and
       readonly builtins.  Each attribute applies to all members of an array.

       Arrays   are  assigned  to  using  compound  assignments  of  the  form
       name=(value1  ...  valuen),  where  each   value   is   of   the   form
       [subscript]=string.   Indexed array assignments do not require anything
       but string.  When assigning to indexed arrays, if the optional brackets
       and  subscript  are  supplied, that index is assigned to; otherwise the
       index of the element assigned is the last  index  assigned  to  by  the
       statement plus one.  Indexing starts at zero.

       When assigning to an associative array, the subscript is required.

       This  syntax is also accepted by the declare builtin.  Individual array
       elements may be assigned  to  using  the  name[subscript]=value  syntax
       introduced  above.   When  assigning  to  an  indexed array, if name is
       subscripted by  a  negative  number,  that  number  is  interpreted  as
       relative  to  one  greater  than the maximum index of name, so negative
       indices count back from the end of  the  array,  and  an  index  of  -1
       references the last element.

       Any  element  of  an  array may be referenced using ${name[subscript]}.
       The braces are required to avoid conflicts with pathname expansion.  If
       subscript  is  @  or *, the word expands to all members of name.  These
       subscripts differ only when the word appears within double quotes.   If
       the word is double-quoted, ${name[*]} expands to a single word with the
       value of each array member separated by the first character of the  IFS
       special  variable,  and  ${name[@]}  expands  each element of name to a
       separate word.  When there are no array members, ${name[@]} expands  to
       nothing.   If  the  double-quoted  expansion  occurs within a word, the
       expansion of the first parameter is joined with the beginning  part  of
       the  original  word,  and the expansion of the last parameter is joined
       with the last part of the original word.   This  is  analogous  to  the
       expansion  of  the  special  parameters * and @ (see Special Parameters
       above).     ${#name[subscript]}    expands    to    the    length    of
       ${name[subscript]}.   If  subscript  is  *  or  @, the expansion is the
       number of elements in the array.  Referencing an array variable without
       a  subscript is equivalent to referencing the array with a subscript of
       0.  If the subscript used to reference an element of an  indexed  array
       evaluates  to a number less than zero, it is interpreted as relative to
       one greater than the maximum index of the array,  so  negative  indices
       count back from the end of the array, and an index of -1 references the
       last element.

       An array variable is considered set if a subscript has been assigned  a
       value.  The null string is a valid value.

       It  is possible to obtain the keys (indices) of an array as well as the
       values.  ${!name[@]} and ${!name[*]} expand to the indices assigned  in
       array variable name.  The treatment when in double quotes is similar to
       the expansion of the special parameters @ and * within double quotes.

       The unset builtin is used to  destroy  arrays.   unset  name[subscript]
       destroys  the array element at index subscript.  Negative subscripts to
       indexed arrays are interpreted as described above.  Care must be  taken
       to  avoid  unwanted  side  effects caused by pathname expansion.  unset
       name, where name is an array, or unset name[subscript], where subscript
       is * or @, removes the entire array.

       The  declare,  local,  and readonly builtins each accept a -a option to
       specify an indexed array and a -A  option  to  specify  an  associative
       array.   If  both  options are supplied, -A takes precedence.  The read
       builtin accepts a -a option to assign a list of  words  read  from  the
       standard input to an array.  The set and declare builtins display array
       values in a way that allows them to be reused as assignments.

EXPANSION

       Expansion is performed on the command line after it has been split into
       words.   There are seven kinds of expansion performed: brace expansion,
       tilde   expansion,   parameter   and   variable   expansion,    command
       substitution,   arithmetic  expansion,  word  splitting,  and  pathname
       expansion.

       The order of expansions is: brace expansion; tilde expansion, parameter
       and  variable expansion, arithmetic expansion, and command substitution
       (done  in  a  left-to-right  fashion);  word  splitting;  and  pathname
       expansion.

       On  systems  that  can  support  it,  there  is an additional expansion
       available: process substitution.  This is performed at the same time as
       tilde,  parameter,  variable,  and  arithmetic  expansion  and  command
       substitution.

       Only brace expansion, word splitting, and pathname expansion can change
       the  number of words of the expansion; other expansions expand a single
       word to a single word.  The only exceptions to this are the  expansions
       of "$@" and "${name[@]}" as explained above (see PARAMETERS).

   Brace Expansion
       Brace  expansion  is  a  mechanism  by  which  arbitrary strings may be
       generated.  This mechanism is similar to pathname  expansion,  but  the
       filenames generated need not exist.  Patterns to be brace expanded take
       the form of an optional preamble, followed by either a series of comma-
       separated  strings  or  a sequence expression between a pair of braces,
       followed by an optional postscript.  The preamble is prefixed  to  each
       string contained within the braces, and the postscript is then appended
       to each resulting string, expanding left to right.

       Brace expansions may be nested.  The results of  each  expanded  string
       are  not  sorted;  left  to  right  order  is  preserved.  For example,
       a{d,c,b}e expands into `ade ace abe'.

       A sequence expression takes the form {x..y[..incr]}, where x and y  are
       either  integers or single characters, and incr, an optional increment,
       is an integer.  When integers are supplied, the expression  expands  to
       each  number  between  x  and  y,  inclusive.  Supplied integers may be
       prefixed with 0 to force each term to have the same width.  When either
       x  or  y  begins with a zero, the shell attempts to force all generated
       terms  to  contain  the  same  number  of  digits,  zero-padding  where
       necessary.   When  characters  are  supplied, the expression expands to
       each character lexicographically between x and y, inclusive, using  the
       default  C  locale.   Note  that both x and y must be of the same type.
       When the increment is supplied, it is used as  the  difference  between
       each term.  The default increment is 1 or -1 as appropriate.

       Brace  expansion  is  performed  before  any  other expansions, and any
       characters special to other expansions are preserved in the result.  It
       is  strictly textual.  Bash does not apply any syntactic interpretation
       to the context of the expansion or the text between the braces.

       A correctly-formed brace expansion must contain  unquoted  opening  and
       closing  braces,  and  at  least one unquoted comma or a valid sequence
       expression.  Any incorrectly formed brace expansion is left  unchanged.
       A { or , may be quoted with a backslash to prevent its being considered
       part  of  a  brace  expression.   To  avoid  conflicts  with  parameter
       expansion,   the  string  ${  is  not  considered  eligible  for  brace
       expansion.

       This construct is typically used as shorthand when the common prefix of
       the strings to be generated is longer than in the above example:

              mkdir /usr/local/src/bash/{old,new,dist,bugs}
       or
              chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}

       Brace  expansion  introduces  a  slight incompatibility with historical
       versions of sh.  sh does not treat opening or closing braces  specially
       when  they  appear as part of a word, and preserves them in the output.
       Bash removes braces from words as a  consequence  of  brace  expansion.
       For  example,  a word entered to sh as file{1,2} appears identically in
       the output.  The same word is output as file1 file2 after expansion  by
       bash.   If strict compatibility with sh is desired, start bash with the
       +B option or disable brace expansion with the  +B  option  to  the  set
       command (see SHELL BUILTIN COMMANDS below).

   Tilde Expansion
       If  a  word  begins  with an unquoted tilde character (`~'), all of the
       characters preceding the first unquoted slash (or  all  characters,  if
       there  is no unquoted slash) are considered a tilde-prefix.  If none of
       the characters in the tilde-prefix are quoted, the  characters  in  the
       tilde-prefix  following the tilde are treated as a possible login name.
       If this login name is the null string, the tilde is replaced  with  the
       value  of  the  shell  parameter  HOME.   If  HOME  is  unset, the home
       directory of the user  executing  the  shell  is  substituted  instead.
       Otherwise,  the  tilde-prefix  is  replaced  with  the  home  directory
       associated with the specified login name.

       If the tilde-prefix is a `~+', the value  of  the  shell  variable  PWD
       replaces the tilde-prefix.  If the tilde-prefix is a `~-', the value of
       the shell variable OLDPWD, if  it  is  set,  is  substituted.   If  the
       characters  following the tilde in the tilde-prefix consist of a number
       N, optionally prefixed by a `+' or a `-', the tilde-prefix is  replaced
       with the corresponding element from the directory stack, as it would be
       displayed by the dirs builtin  invoked  with  the  tilde-prefix  as  an
       argument.   If  the  characters following the tilde in the tilde-prefix
       consist of a number without a leading `+' or `-', `+' is assumed.

       If the login name is invalid, or the tilde expansion fails, the word is
       unchanged.

       Each   variable  assignment  is  checked  for  unquoted  tilde-prefixes
       immediately following a : or  the  first  =.   In  these  cases,  tilde
       expansion  is also performed.  Consequently, one may use filenames with
       tildes in assignments to PATH, MAILPATH,  and  CDPATH,  and  the  shell
       assigns the expanded value.

   Parameter Expansion
       The `$' character introduces parameter expansion, command substitution,
       or arithmetic expansion.  The parameter name or symbol to  be  expanded
       may  be enclosed in braces, which are optional but serve to protect the
       variable to be expanded from characters immediately following it  which
       could be interpreted as part of the name.

       When  braces  are  used, the matching ending brace is the first `}' not
       escaped by a backslash or within a quoted string,  and  not  within  an
       embedded  arithmetic  expansion,  command  substitution,  or  parameter
       expansion.

       ${parameter}
              The value of parameter is substituted.  The braces are  required
              when  parameter  is  a  positional  parameter with more than one
              digit, or when parameter is followed by a character which is not
              to be interpreted as part of its name.  The parameter is a shell
              parameter as described above PARAMETERS) or an  array  reference
              (Arrays).

       If  the  first  character  of parameter is an exclamation point (!), it
       introduces a level of variable indirection.  Bash uses the value of the
       variable formed from the rest of parameter as the name of the variable;
       this variable is then expanded and that value is used in  the  rest  of
       the  substitution,  rather than the value of parameter itself.  This is
       known as indirect expansion.  The exceptions to this are the expansions
       of  ${!prefix*} and ${!name[@]} described below.  The exclamation point
       must  immediately  follow  the  left  brace  in  order   to   introduce
       indirection.

       In  each  of  the  cases  below,  word  is  subject to tilde expansion,
       parameter expansion, command substitution, and arithmetic expansion.

       When not performing substring expansion,  using  the  forms  documented
       below  (e.g.,  :-),  bash  tests for a parameter that is unset or null.
       Omitting the colon results in a test  only  for  a  parameter  that  is
       unset.

       ${parameter:-word}
              Use  Default  Values.   If  parameter  is  unset  or  null,  the
              expansion of word  is  substituted.   Otherwise,  the  value  of
              parameter is substituted.
       ${parameter:=word}
              Assign  Default  Values.   If  parameter  is  unset or null, the
              expansion of word  is  assigned  to  parameter.   The  value  of
              parameter   is  then  substituted.   Positional  parameters  and
              special parameters may not be assigned to in this way.
       ${parameter:?word}
              Display Error if Null or Unset.  If parameter is null or  unset,
              the  expansion  of  word (or a message to that effect if word is
              not present) is written to the standard error and the shell,  if
              it is not interactive, exits.  Otherwise, the value of parameter
              is substituted.
       ${parameter:+word}
              Use Alternate Value.  If parameter is null or unset, nothing  is
              substituted, otherwise the expansion of word is substituted.
       ${parameter:offset}
       ${parameter:offset:length}
              Substring  Expansion.  Expands to up to length characters of the
              value of  parameter  starting  at  the  character  specified  by
              offset.  If parameter is @, an indexed array subscripted by @ or
              *, or an associative array name, the results differ as described
              below.   If  length  is omitted, expands to the substring of the
              value of parameter starting at the character specified by offset
              and  extending  to  the end of the value.  length and offset are
              arithmetic expressions (see ARITHMETIC EVALUATION below).

              If offset evaluates to a number less than  zero,  the  value  is
              used  as  an  offset  in characters from the end of the value of
              parameter.  If length evaluates to a number less than  zero,  it
              is  interpreted  as  an offset in characters from the end of the
              value of parameter rather than a number of characters,  and  the
              expansion  is  the  characters  between  offset and that result.
              Note that a negative offset must be separated from the colon  by
              at  least  one  space  to  avoid  being  confused  with  the  :-
              expansion.

              If parameter is @, the result is  length  positional  parameters
              beginning at offset.  A negative offset is taken relative to one
              greater than the greatest positional parameter, so an offset  of
              -1  evaluates  to  the  last  positional  parameter.   It  is an
              expansion error if length evaluates to a number less than zero.

              If parameter is an indexed array name subscripted by @ or *, the
              result  is  the  length  members  of  the  array  beginning with
              ${parameter[offset]}.  A negative offset is  taken  relative  to
              one  greater  than the maximum index of the specified array.  It
              is an expansion error if length evaluates to a number less  than
              zero.

              Substring  expansion  applied  to  an associative array produces
              undefined results.

              Substring  indexing  is   zero-based   unless   the   positional
              parameters  are  used, in which case the indexing starts at 1 by
              default.  If offset is 0,  and  the  positional  parameters  are
              used, $0 is prefixed to the list.

       ${!prefix*}
       ${!prefix@}
              Names  matching prefix.  Expands to the names of variables whose
              names begin with prefix, separated by the first character of the
              IFS  special variable.  When @ is used and the expansion appears
              within double quotes, each variable name expands to  a  separate
              word.

       ${!name[@]}
       ${!name[*]}
              List  of  array  keys.  If name is an array variable, expands to
              the list of array indices (keys) assigned in name.  If  name  is
              not  an  array,  expands to 0 if name is set and null otherwise.
              When @ is used and the expansion appears within  double  quotes,
              each key expands to a separate word.

       ${#parameter}
              Parameter  length.   The  length  in  characters of the value of
              parameter is substituted.  If parameter is *  or  @,  the  value
              substituted   is   the  number  of  positional  parameters.   If
              parameter is an array name subscripted by  *  or  @,  the  value
              substituted  is  the  number  of  elements  in  the  array.   If
              parameter is an indexed array name  subscripted  by  a  negative
              number,  that  number  is interpreted as relative to one greater
              than the maximum index of parameter, so negative  indices  count
              back  from  the  end of the array, and an index of -1 references
              the last element.

       ${parameter#word}
       ${parameter##word}
              Remove matching prefix pattern.  The word is expanded to produce
              a pattern just as in pathname expansion.  If the pattern matches
              the beginning of the value of parameter, then the result of  the
              expansion  is  the expanded value of parameter with the shortest
              matching pattern  (the  ``#''  case)  or  the  longest  matching
              pattern  (the ``##'' case) deleted.  If parameter is @ or *, the
              pattern  removal  operation  is  applied  to   each   positional
              parameter  in turn, and the expansion is the resultant list.  If
              parameter is an array variable subscripted  with  @  or  *,  the
              pattern removal operation is applied to each member of the array
              in turn, and the expansion is the resultant list.

       ${parameter%word}
       ${parameter%%word}
              Remove matching suffix pattern.  The word is expanded to produce
              a pattern just as in pathname expansion.  If the pattern matches
              a trailing portion of the expanded value of parameter, then  the
              result  of the expansion is the expanded value of parameter with
              the shortest matching pattern (the ``%'' case)  or  the  longest
              matching  pattern  (the ``%%'' case) deleted.  If parameter is @
              or  *,  the  pattern  removal  operation  is  applied  to   each
              positional parameter in turn, and the expansion is the resultant
              list.  If parameter is an array variable subscripted with  @  or
              *,  the  pattern  removal operation is applied to each member of
              the array in turn, and the expansion is the resultant list.

       ${parameter/pattern/string}
              Pattern substitution.  The pattern  is  expanded  to  produce  a
              pattern  just  as  in pathname expansion.  Parameter is expanded
              and the longest match of pattern against its value  is  replaced
              with  string.   If pattern begins with /, all matches of pattern
              are replaced with string.  Normally  only  the  first  match  is
              replaced.   If  pattern  begins  with  #,  it  must match at the
              beginning of the expanded value of parameter.  If pattern begins
              with  %,  it  must  match  at  the  end of the expanded value of
              parameter.  If string is null, matches of  pattern  are  deleted
              and  the  / following pattern may be omitted.  If parameter is @
              or *, the substitution operation is applied to  each  positional
              parameter  in turn, and the expansion is the resultant list.  If
              parameter is an array variable subscripted  with  @  or  *,  the
              substitution operation is applied to each member of the array in
              turn, and the expansion is the resultant list.

       ${parameter^pattern}
       ${parameter^^pattern}
       ${parameter,pattern}
       ${parameter,,pattern}
              Case  modification.   This  expansion  modifies  the   case   of
              alphabetic  characters in parameter.  The pattern is expanded to
              produce a pattern just as in pathname expansion.  Each character
              in  the  expanded  value of parameter is tested against pattern,
              and, if it matches the pattern,  its  case  is  converted.   The
              pattern  should  not  attempt  to match more than one character.
              The ^ operator converts lowercase letters  matching  pattern  to
              uppercase; the , operator converts matching uppercase letters to
              lowercase.  The  ^^  and  ,,  expansions  convert  each  matched
              character  in  the  expanded value; the ^ and , expansions match
              and convert only the first character in the expanded value.   If
              pattern  is omitted, it is treated like a ?, which matches every
              character.  If parameter  is  @  or  *,  the  case  modification
              operation  is  applied to each positional parameter in turn, and
              the expansion is the resultant list.  If parameter is  an  array
              variable   subscripted  with  @  or  *,  the  case  modification
              operation is applied to each member of the array  in  turn,  and
              the expansion is the resultant list.

   Command Substitution
       Command  substitution  allows  the  output  of a command to replace the
       command name.  There are two forms:

              $(command)
       or
              `command`

       Bash performs the expansion by  executing  command  and  replacing  the
       command  substitution with the standard output of the command, with any
       trailing newlines deleted.  Embedded newlines are not deleted, but they
       may  be  removed during word splitting.  The command substitution $(cat
       file) can be replaced by the equivalent but faster $(< file).

       When the old-style backquote form of substitution  is  used,  backslash
       retains  its  literal  meaning except when followed by $, `, or \.  The
       first backquote not preceded by  a  backslash  terminates  the  command
       substitution.   When  using the $(command) form, all characters between
       the parentheses make up the command; none are treated specially.

       Command substitutions may be nested.  To nest when using the backquoted
       form, escape the inner backquotes with backslashes.

       If  the  substitution  appears within double quotes, word splitting and
       pathname expansion are not performed on the results.

   Arithmetic Expansion
       Arithmetic expansion allows the evaluation of an arithmetic  expression
       and  the  substitution  of  the  result.   The  format  for  arithmetic
       expansion is:

              $((expression))

       The old format $[expression] is  deprecated  and  will  be  removed  in
       upcoming versions of bash.

       The  expression  is  treated  as if it were within double quotes, but a
       double quote inside the parentheses  is  not  treated  specially.   All
       tokens  in  the  expression  undergo  parameter and variable expansion,
       command substitution, and quote removal.  The result is treated as  the
       arithmetic  expression  to  be evaluated.  Arithmetic expansions may be
       nested.

       The evaluation is performed according to the rules listed  below  under
       ARITHMETIC EVALUATION.  If expression is invalid, bash prints a message
       indicating failure and no substitution occurs.

   Process Substitution
       Process substitution is supported on systems that support  named  pipes
       (FIFOs)  or the /dev/fd method of naming open files.  It takes the form
       of <(list) or >(list).  The process list  is  run  with  its  input  or
       output  connected  to a FIFO or some file in /dev/fd.  The name of this
       file is passed as an argument to the current command as the  result  of
       the  expansion.   If the >(list) form is used, writing to the file will
       provide input for list.  If the <(list) form is used, the  file  passed
       as an argument should be read to obtain the output of list.

       When  available,  process substitution is performed simultaneously with
       parameter and variable expansion, command substitution, and  arithmetic
       expansion.

   Word Splitting
       The   shell   scans   the   results  of  parameter  expansion,  command
       substitution, and arithmetic expansion that did not occur within double
       quotes for word splitting.

       The  shell  treats each character of IFS as a delimiter, and splits the
       results of the other expansions into words using  these  characters  as
       field   terminators.   If  IFS  is  unset,  or  its  value  is  exactly
       <space><tab><newline>, the default, then sequences of  <space>,  <tab>,
       and  <newline>  at the beginning and end of the results of the previous
       expansions are ignored, and any sequence of IFS characters not  at  the
       beginning  or  end  serves  to delimit words.  If IFS has a value other
       than the default, then sequences of the whitespace characters space and
       tab  are  ignored  at the beginning and end of the word, as long as the
       whitespace character  is  in  the  value  of  IFS  (an  IFS  whitespace
       character).   Any  character  in  IFS that is not IFS whitespace, along
       with any adjacent IFS  whitespace  characters,  delimits  a  field.   A
       sequence  of  IFS whitespace characters is also treated as a delimiter.
       If the value of IFS is null, no word splitting occurs.

       Explicit null arguments ("" or '')  are  retained.   Unquoted  implicit
       null arguments, resulting from the expansion of parameters that have no
       values, are removed.  If a parameter with no value is  expanded  within
       double quotes, a null argument results and is retained.

       Note that if no expansion occurs, no splitting is performed.

   Pathname Expansion
       After  word  splitting,  unless  the -f option has been set, bash scans
       each word for the characters *, ?, and [.  If one of  these  characters
       appears,  then  the word is regarded as a pattern, and replaced with an
       alphabetically sorted list  of  filenames  matching  the  pattern  (see
       Pattern  Matching  below).  If no matching filenames are found, and the
       shell option nullglob is not enabled, the word is left  unchanged.   If
       the  nullglob  option  is  set,  and  no matches are found, the word is
       removed.  If the failglob shell option  is  set,  and  no  matches  are
       found, an error message is printed and the command is not executed.  If
       the shell option nocaseglob is enabled, the match is performed  without
       regard  to  the  case  of  alphabetic characters.  Note that when using
       range expressions like [a-z] (see below), letters of the other case may
       be included, depending on the setting of LC_COLLATE.  When a pattern is
       used for pathname expansion, the character ``.''  at  the  start  of  a
       name  or  immediately  following  a  slash  must be matched explicitly,
       unless the shell option dotglob is set.  When matching a pathname,  the
       slash character must always be matched explicitly.  In other cases, the
       ``.''  character is not treated  specially.   See  the  description  of
       shopt  below  under  SHELL  BUILTIN  COMMANDS  for a description of the
       nocaseglob, nullglob, failglob, and dotglob shell options.

       The GLOBIGNORE shell variable may  be  used  to  restrict  the  set  of
       filenames  matching  a  pattern.   If  GLOBIGNORE is set, each matching
       filename that also matches one of the patterns in GLOBIGNORE is removed
       from  the list of matches.  The filenames ``.''  and ``..''  are always
       ignored  when  GLOBIGNORE  is  set  and  not  null.   However,  setting
       GLOBIGNORE  to  a non-null value has the effect of enabling the dotglob
       shell option, so all other  filenames  beginning  with  a  ``.''   will
       match.   To get the old behavior of ignoring filenames beginning with a
       ``.'', make ``.*''  one of the patterns  in  GLOBIGNORE.   The  dotglob
       option is disabled when GLOBIGNORE is unset.

       Pattern Matching

       Any character that appears in a pattern, other than the special pattern
       characters described below, matches itself.  The NUL character may  not
       occur  in  a pattern.  A backslash escapes the following character; the
       escaping backslash is discarded when  matching.   The  special  pattern
       characters must be quoted if they are to be matched literally.

       The special pattern characters have the following meanings:

              *      Matches  any string, including the null string.  When the
                     globstar shell option is enabled, and  *  is  used  in  a
                     pathname  expansion  context,  two  adjacent *s used as a
                     single pattern will match all  files  and  zero  or  more
                     directories  and subdirectories.  If followed by a /, two
                     adjacent   *s   will   match   only    directories    and
                     subdirectories.
              ?      Matches any single character.
              [...]  Matches  any  one  of the enclosed characters.  A pair of
                     characters  separated  by  a  hyphen  denotes   a   range
                     expression;  any  character  that falls between those two
                     characters,  inclusive,  using   the   current   locale's
                     collating sequence and character set, is matched.  If the
                     first character following the [ is a !  or a ^  then  any
                     character  not enclosed is matched.  The sorting order of
                     characters in range  expressions  is  determined  by  the
                     current locale and the values of the LC_COLLATE or LC_ALL
                     shell variables,  if  set.   To  obtain  the  traditional
                     interpretation  of  range  expressions,  where  [a-d]  is
                     equivalent to [abcd],  set  value  of  the  LC_ALL  shell
                     variable  to  C,  or  enable  the  globasciiranges  shell
                     option.  A - may be matched by including it as the  first
                     or  last  character  in  the  set.  A ] may be matched by
                     including it as the first character in the set.

                     Within [ and ], character classes can be specified  using
                     the syntax [:class:], where class is one of the following
                     classes defined in the POSIX standard:
                     alnum alpha ascii blank cntrl  digit  graph  lower  print
                     punct space upper word xdigit
                     A character class matches any character belonging to that
                     class.  The word character class matches letters, digits,
                     and the character _.

                     Within  [  and  ],  an equivalence class can be specified
                     using the syntax [=c=], which matches all characters with
                     the  same  collation  weight  (as  defined by the current
                     locale) as the character c.

                     Within  [  and  ],  the  syntax  [.symbol.]  matches  the
                     collating symbol symbol.

       If the extglob shell option is enabled using the shopt builtin, several
       extended pattern matching operators are recognized.  In  the  following
       description, a pattern-list is a list of one or more patterns separated
       by a |.  Composite patterns may be formed using  one  or  more  of  the
       following sub-patterns:

              ?(pattern-list)
                     Matches zero or one occurrence of the given patterns
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns
              +(pattern-list)
                     Matches one or more occurrences of the given patterns
              @(pattern-list)
                     Matches one of the given patterns
              !(pattern-list)
                     Matches anything except one of the given patterns

   Quote Removal
       After  the  preceding  expansions,  all  unquoted  occurrences  of  the
       characters \, ', and " that did  not  result  from  one  of  the  above
       expansions are removed.

REDIRECTION

       Before  a  command  is executed, its input and output may be redirected
       using a special notation interpreted by the shell.  Redirection  allows
       commands'  file handles to be duplicated, opened, closed, made to refer
       to different files, and can change the files the command reads from and
       writes  to.  Redirection may also be used to modify file handles in the
       current  shell  execution  environment.   The   following   redirection
       operators may precede or appear anywhere within a simple command or may
       follow a command.  Redirections are processed in the order they appear,
       from left to right.

       Each  redirection  that may be preceded by a file descriptor number may
       instead be preceded by a word of the form {varname}.  In this case, for
       each redirection operator except >&- and <&-, the shell will allocate a
       file descriptor greater than or equal to 10 and assign it  to  varname.
       If  >&-  or  <&- is preceded by {varname}, the value of varname defines
       the file descriptor to close.

       In the  following  descriptions,  if  the  file  descriptor  number  is
       omitted,  and the first character of the redirection operator is <, the
       redirection refers to the standard input (file descriptor 0).   If  the
       first  character  of  the  redirection  operator  is >, the redirection
       refers to the standard output (file descriptor 1).

       The  word  following  the  redirection  operator   in   the   following
       descriptions,  unless otherwise noted, is subjected to brace expansion,
       tilde   expansion,   parameter   and   variable   expansion,    command
       substitution,  arithmetic expansion, quote removal, pathname expansion,
       and word splitting.  If it expands to more than one word, bash  reports
       an error.

       Note  that  the order of redirections is significant.  For example, the
       command

              ls > dirlist 2>&1

       directs both standard output and standard error to  the  file  dirlist,
       while the command

              ls 2>&1 > dirlist

       directs  only the standard output to file dirlist, because the standard
       error was duplicated from  the  standard  output  before  the  standard
       output was redirected to dirlist.

       Bash  handles  several  filenames  specially  when  they  are  used  in
       redirections, as described in the following table:

              /dev/fd/fd
                     If  fd  is  a  valid  integer,  file  descriptor  fd   is
                     duplicated.
              /dev/stdin
                     File descriptor 0 is duplicated.
              /dev/stdout
                     File descriptor 1 is duplicated.
              /dev/stderr
                     File descriptor 2 is duplicated.
              /dev/tcp/host/port
                     If host is a valid hostname or Internet address, and port
                     is an integer port number or service name, bash  attempts
                     to open the corresponding TCP socket.
              /dev/udp/host/port
                     If host is a valid hostname or Internet address, and port
                     is an integer port number or service name, bash  attempts
                     to open the corresponding UDP socket.

       A failure to open or create a file causes the redirection to fail.

       Redirections  using file descriptors greater than 9 should be used with
       care, as they  may  conflict  with  file  descriptors  the  shell  uses
       internally.

       Note that the exec builtin command can make redirections take effect in
       the current shell.

   Redirecting Input
       Redirection of input causes  the  file  whose  name  results  from  the
       expansion of word to be opened for reading on file descriptor n, or the
       standard input (file descriptor 0) if n is not specified.

       The general format for redirecting input is:

              [n]<word

   Redirecting Output
       Redirection of output causes the  file  whose  name  results  from  the
       expansion of word to be opened for writing on file descriptor n, or the
       standard output (file descriptor 1) if n is not specified.  If the file
       does  not exist it is created; if it does exist it is truncated to zero
       size.

       The general format for redirecting output is:

              [n]>word

       If the redirection operator is >, and the noclobber option to  the  set
       builtin  has  been enabled, the redirection will fail if the file whose
       name results from the expansion of word exists and is a  regular  file.
       If the redirection operator is >|, or the redirection operator is > and
       the noclobber option to the set builtin command  is  not  enabled,  the
       redirection is attempted even if the file named by word exists.

   Appending Redirected Output
       Redirection  of  output  in  this  fashion  causes  the file whose name
       results from the expansion of word to be opened for appending  on  file
       descriptor  n,  or  the standard output (file descriptor 1) if n is not
       specified.  If the file does not exist it is created.

       The general format for appending output is:

              [n]>>word

   Redirecting Standard Output and Standard Error
       This construct allows both the standard output (file descriptor 1)  and
       the  standard  error output (file descriptor 2) to be redirected to the
       file whose name is the expansion of word.

       There are two formats for  redirecting  standard  output  and  standard
       error:

              &>word
       and
              >&word

       Of  the  two  forms,  the  first  is  preferred.   This is semantically
       equivalent to

              >word 2>&1

       When using the second form, word may not expand to a number or  -.   If
       it  does,  other  redirection  operators  apply  (see  Duplicating File
       Descriptors below) for compatibility reasons.

   Appending Standard Output and Standard Error
       This construct allows both the standard output (file descriptor 1)  and
       the  standard  error  output  (file descriptor 2) to be appended to the
       file whose name is the expansion of word.

       The format for appending standard output and standard error is:

              &>>word

       This is semantically equivalent to

              >>word 2>&1

       (see Duplicating File Descriptors below).

   Here Documents
       This type of redirection instructs the shell to  read  input  from  the
       current source until a line containing only delimiter (with no trailing
       blanks) is seen.  All of the lines read up to that point are then  used
       as the standard input for a command.

       The format of here-documents is:

              <<[-]word
                      here-document
              delimiter

       No  parameter  and variable expansion, command substitution, arithmetic
       expansion,  or  pathname  expansion  is  performed  on  word.   If  any
       characters  in  word  are  quoted, the delimiter is the result of quote
       removal on word, and the lines in the here-document are  not  expanded.
       If  word  is  unquoted, all lines of the here-document are subjected to
       parameter expansion, command substitution,  and  arithmetic  expansion,
       the  character  sequence  \<newline>  is ignored, and \ must be used to
       quote the characters \, $, and `.

       If the redirection operator is <<-, then all leading tab characters are
       stripped  from  input  lines  and  the line containing delimiter.  This
       allows here-documents within shell scripts to be indented in a  natural
       fashion.

   Here Strings
       A variant of here documents, the format is:

              <<<word

       The  word  undergoes  brace  expansion,  tilde expansion, parameter and
       variable expansion, command  substitution,  arithmetic  expansion,  and
       quote   removal.    Pathname  expansion  and  word  splitting  are  not
       performed.  The result is supplied as a single string to the command on
       its standard input.

   Duplicating File Descriptors
       The redirection operator

              [n]<&word

       is used to duplicate input file descriptors.  If word expands to one or
       more digits, the file descriptor denoted by n is made to be a  copy  of
       that  file  descriptor.   If  the  digits in word do not specify a file
       descriptor open  for  input,  a  redirection  error  occurs.   If  word
       evaluates  to  -,  file descriptor n is closed.  If n is not specified,
       the standard input (file descriptor 0) is used.

       The operator

              [n]>&word

       is used similarly to duplicate output file descriptors.  If  n  is  not
       specified,  the  standard  output  (file descriptor 1) is used.  If the
       digits in word do not specify a file  descriptor  open  for  output,  a
       redirection error occurs.  If word evaluates to -, file descriptor n is
       closed.  As a special case, if n is omitted, and word does  not  expand
       to  one or more digits or -, the standard output and standard error are
       redirected as described previously.

   Moving File Descriptors
       The redirection operator

              [n]<&digit-

       moves the file descriptor digit to file descriptor n, or  the  standard
       input (file descriptor 0) if n is not specified.  digit is closed after
       being duplicated to n.

       Similarly, the redirection operator

              [n]>&digit-

       moves the file descriptor digit to file descriptor n, or  the  standard
       output (file descriptor 1) if n is not specified.

   Opening File Descriptors for Reading and Writing
       The redirection operator

              [n]<>word

       causes  the  file  whose name is the expansion of word to be opened for
       both reading and writing on file descriptor n, or on file descriptor  0
       if n is not specified.  If the file does not exist, it is created.

ALIASES

       Aliases  allow a string to be substituted for a word when it is used as
       the first word of a simple command.  The  shell  maintains  a  list  of
       aliases  that  may  be set and unset with the alias and unalias builtin
       commands (see SHELL BUILTIN COMMANDS below).  The first  word  of  each
       simple  command, if unquoted, is checked to see if it has an alias.  If
       so, that word is replaced by the text of the alias.  The characters  /,
       $,  `,  and = and any of the shell metacharacters or quoting characters
       listed above may not appear in an alias name.  The replacement text may
       contain  any  valid  shell  input, including shell metacharacters.  The
       first word of the replacement text is tested for aliases,  but  a  word
       that  is  identical to an alias being expanded is not expanded a second
       time.  This means that one may alias ls to ls  -F,  for  instance,  and
       bash  does  not try to recursively expand the replacement text.  If the
       last character of the alias value is a blank,  then  the  next  command
       word following the alias is also checked for alias expansion.

       Aliases are created and listed with the alias command, and removed with
       the unalias command.

       There is no mechanism for using arguments in the replacement text.   If
       arguments  are  needed,  a shell function should be used (see FUNCTIONS
       below).

       Aliases are not expanded when the shell is not interactive, unless  the
       expand_aliases  shell option is set using shopt (see the description of
       shopt under SHELL BUILTIN COMMANDS below).

       The rules concerning the definition and use  of  aliases  are  somewhat
       confusing.   Bash  always  reads  at  least  one complete line of input
       before executing any  of  the  commands  on  that  line.   Aliases  are
       expanded  when  a command is read, not when it is executed.  Therefore,
       an alias definition appearing on the same line as another command  does
       not  take  effect  until  the next line of input is read.  The commands
       following the alias definition on that line are not affected by the new
       alias.   This  behavior  is  also an issue when functions are executed.
       Aliases are expanded when a function definition is read, not  when  the
       function  is  executed,  because  a  function  definition  is  itself a
       compound command.  As a consequence, aliases defined in a function  are
       not  available  until  after  that  function  is executed.  To be safe,
       always put alias definitions on a separate line, and do not  use  alias
       in compound commands.

       For almost every purpose, aliases are superseded by shell functions.

FUNCTIONS

       A  shell  function,  defined  as  described  above under SHELL GRAMMAR,
       stores a series of commands for later execution.  When the  name  of  a
       shell  function  is used as a simple command name, the list of commands
       associated with that function name is executed.  Functions are executed
       in  the  context  of  the  current  shell; no new process is created to
       interpret them (contrast this with the execution of  a  shell  script).
       When  a  function is executed, the arguments to the function become the
       positional parameters during its execution.  The special parameter # is
       updated  to reflect the change.  Special parameter 0 is unchanged.  The
       first element of the FUNCNAME variable  is  set  to  the  name  of  the
       function while the function is executing.

       All  other  aspects  of  the  shell execution environment are identical
       between a function and its caller with these exceptions:  the DEBUG and
       RETURN  traps  (see  the  description  of  the trap builtin under SHELL
       BUILTIN COMMANDS below) are not inherited unless the function has  been
       given  the  trace attribute (see the description of the declare builtin
       below) or the -o functrace shell option has been enabled with  the  set
       builtin  (in  which  case  all  functions  inherit the DEBUG and RETURN
       traps), and the ERR trap is not inherited unless the -o errtrace  shell
       option has been enabled.

       Variables  local to the function may be declared with the local builtin
       command.  Ordinarily, variables and their values are shared between the
       function and its caller.

       The  FUNCNEST  variable,  if  set  to  a  numeric value greater than 0,
       defines a maximum function nesting level.   Function  invocations  that
       exceed the limit cause the entire command to abort.

       If  the  builtin command return is executed in a function, the function
       completes and  execution  resumes  with  the  next  command  after  the
       function call.  Any command associated with the RETURN trap is executed
       before execution resumes.  When a function completes, the values of the
       positional  parameters  and the special parameter # are restored to the
       values they had prior to the function's execution.

       Function names and definitions may be listed with the -f option to  the
       declare  or  typeset  builtin  commands.   The  -F option to declare or
       typeset will list the function names only (and  optionally  the  source
       file  and  line  number,  if  the  extdebug  shell  option is enabled).
       Functions may be exported so that  subshells  automatically  have  them
       defined  with  the  -f  option  to  the  export  builtin.   A  function
       definition may be deleted using the -f option  to  the  unset  builtin.
       Note  that  shell functions and variables with the same name may result
       in multiple identically-named entries in the environment passed to  the
       shell's children.  Care should be taken in cases where this may cause a
       problem.

       Functions may be recursive.  The FUNCNEST variable may be used to limit
       the  depth  of  the  function  call  stack  and  restrict the number of
       function invocations.  By default, no limit is imposed on the number of
       recursive calls.

ARITHMETIC EVALUATION

       The  shell allows arithmetic expressions to be evaluated, under certain
       circumstances (see the let and declare builtin commands and  Arithmetic
       Expansion).   Evaluation  is done in fixed-width integers with no check
       for overflow, though division by 0 is trapped and flagged as an  error.
       The  operators  and their precedence, associativity, and values are the
       same as in the C language.  The following list of operators is  grouped
       into  levels  of  equal-precedence operators.  The levels are listed in
       order of decreasing precedence.

       id++ id--
              variable post-increment and post-decrement
       ++id --id
              variable pre-increment and pre-decrement
       - +    unary minus and plus
       ! ~    logical and bitwise negation
       **     exponentiation
       * / %  multiplication, division, remainder
       + -    addition, subtraction
       << >>  left and right bitwise shifts
       <= >= < >
              comparison
       == !=  equality and inequality
       &      bitwise AND
       ^      bitwise exclusive OR
       |      bitwise OR
       &&     logical AND
       ||     logical OR
       expr?expr:expr
              conditional operator
       = *= /= %= += -= <<= >>= &= ^= |=
              assignment
       expr1 , expr2
              comma

       Shell  variables  are  allowed  as  operands;  parameter  expansion  is
       performed  before  the  expression is evaluated.  Within an expression,
       shell variables may also  be  referenced  by  name  without  using  the
       parameter  expansion  syntax.   A  shell variable that is null or unset
       evaluates to 0 when referenced by  name  without  using  the  parameter
       expansion  syntax.   The  value  of  a  variable  is  evaluated  as  an
       arithmetic expression when it is referenced, or when a  variable  which
       has  been  given  the  integer attribute using declare -i is assigned a
       value.  A null value evaluates to 0.  A shell variable  need  not  have
       its integer attribute turned on to be used in an expression.

       Constants with a leading 0 are interpreted as octal numbers.  A leading
       0x or  0X  denotes  hexadecimal.   Otherwise,  numbers  take  the  form
       [base#]n,  where the optional base is a decimal number between 2 and 64
       representing the arithmetic base, and n is a number in that  base.   If
       base#  is omitted, then base 10 is used.  When specifying n, the digits
       greater< than 9 are represented by the lowercase letters, the uppercase
       letters, @, and _, in that order.  If base is less than or equal to 36,
       lowercase  and  uppercase  letters  may  be  used  interchangeably   to
       represent numbers between 10 and 35.

       Operators  are  evaluated  in  order of precedence.  Sub-expressions in
       parentheses are evaluated first and may override the  precedence  rules
       above.

CONDITIONAL EXPRESSIONS

       Conditional  expressions  are  used  by the [[ compound command and the
       test and [ builtin commands to test file attributes and perform  string
       and  arithmetic comparisons.  Expressions are formed from the following
       unary or binary  primaries.   If  any  file  argument  to  one  of  the
       primaries  is of the form /dev/fd/n, then file descriptor n is checked.
       If the file argument to one of the  primaries  is  one  of  /dev/stdin,
       /dev/stdout,  or /dev/stderr, file descriptor 0, 1, or 2, respectively,
       is checked.

       Unless otherwise specified, primaries  that  operate  on  files  follow
       symbolic  links  and operate on the target of the link, rather than the
       link itself.

       When used with [[, the < and > operators sort  lexicographically  using
       the current locale.  The test command sorts using ASCII ordering.

       -a file
              True if file exists.
       -b file
              True if file exists and is a block special file.
       -c file
              True if file exists and is a character special file.
       -d file
              True if file exists and is a directory.
       -e file
              True if file exists.
       -f file
              True if file exists and is a regular file.
       -g file
              True if file exists and is set-group-id.
       -h file
              True if file exists and is a symbolic link.
       -k file
              True if file exists and its ``sticky'' bit is set.
       -p file
              True if file exists and is a named pipe (FIFO).
       -r file
              True if file exists and is readable.
       -s file
              True if file exists and has a size greater than zero.
       -t fd  True if file descriptor fd is open and refers to a terminal.
       -u file
              True if file exists and its set-user-id bit is set.
       -w file
              True if file exists and is writable.
       -x file
              True if file exists and is executable.
       -G file
              True if file exists and is owned by the effective group id.
       -L file
              True if file exists and is a symbolic link.
       -N file
              True  if  file  exists  and  has been modified since it was last
              read.
       -O file
              True if file exists and is owned by the effective user id.
       -S file
              True if file exists and is a socket.
       file1 -ef file2
              True if file1 and file2 refer  to  the  same  device  and  inode
              numbers.
       file1 -nt file2
              True  if  file1  is  newer (according to modification date) than
              file2, or if file1 exists and file2 does not.
       file1 -ot file2
              True if file1 is older than file2, or if file2 exists and  file1
              does not.
       -o optname
              True  if  the  shell option optname is enabled.  See the list of
              options under the description  of  the  -o  option  to  the  set
              builtin below.
       -v varname
              True  if  the shell variable varname is set (has been assigned a
              value).
       -R varname
              True if the  shell  variable  varname  is  set  and  is  a  name
              reference.
       -z string
              True if the length of string is zero.
       string
       -n string
              True if the length of string is non-zero.

       string1 == string2
       string1 = string2
              True  if  the strings are equal.  = should be used with the test
              command for POSIX conformance.  When used with the  [[  command,
              this  performs  pattern  matching  as  described above (Compound
              Commands).

       string1 != string2
              True if the strings are not equal.

       string1 < string2
              True if string1 sorts before string2 lexicographically.

       string1 > string2
              True if string1 sorts after string2 lexicographically.

       arg1 OP arg2
              OP is one of -eq, -ne, -lt, -le, -gt, or -ge.  These  arithmetic
              binary  operators return true if arg1 is equal to, not equal to,
              less than, less than or equal to, greater than, or greater  than
              or  equal  to arg2, respectively.  Arg1 and arg2 may be positive
              or negative integers.

SIMPLE COMMAND EXPANSION

       When a simple command is executed, the  shell  performs  the  following
       expansions, assignments, and redirections, from left to right.

       1.     The  words  that  the  parser has marked as variable assignments
              (those preceding the command name) and  redirections  are  saved
              for later processing.

       2.     The  words that are not variable assignments or redirections are
              expanded.  If any words remain after expansion, the  first  word
              is  taken  to be the name of the command and the remaining words
              are the arguments.

       3.     Redirections are performed as described above under REDIRECTION.

       4.     The text after the = in each variable assignment undergoes tilde
              expansion, parameter expansion, command substitution, arithmetic
              expansion, and  quote  removal  before  being  assigned  to  the
              variable.

       If no command name results, the variable assignments affect the current
       shell  environment.   Otherwise,  the  variables  are  added   to   the
       environment of the executed command and do not affect the current shell
       environment.  If any of the assignments attempts to assign a value to a
       readonly  variable,  an error occurs, and the command exits with a non-
       zero status.

       If no command name results, redirections  are  performed,  but  do  not
       affect  the  current shell environment.  A redirection error causes the
       command to exit with a non-zero status.

       If there is a command name left after expansion, execution proceeds  as
       described  below.   Otherwise,  the  command  exits.   If  one  of  the
       expansions contained a command substitution, the  exit  status  of  the
       command  is the exit status of the last command substitution performed.
       If there were no command substitutions, the command exits with a status
       of zero.

COMMAND EXECUTION

       After  a  command  has been split into words, if it results in a simple
       command and an optional list of arguments, the  following  actions  are
       taken.

       If  the  command name contains no slashes, the shell attempts to locate
       it.  If there exists a shell function by that name,  that  function  is
       invoked  as described above in FUNCTIONS.  If the name does not match a
       function, the shell searches for it in the list of shell builtins.   If
       a match is found, that builtin is invoked.

       If  the name is neither a shell function nor a builtin, and contains no
       slashes, bash searches  each  element  of  the  PATH  for  a  directory
       containing  an executable file by that name.  Bash uses a hash table to
       remember the full pathnames of executable files (see hash  under  SHELL
       BUILTIN  COMMANDS  below).  A full search of the directories in PATH is
       performed only if the command is not found in the hash table.   If  the
       search is unsuccessful, the shell searches for a defined shell function
       named command_not_found_handle.  If that function exists, it is invoked
       with  the  original command and the original command's arguments as its
       arguments, and the function's exit status becomes the  exit  status  of
       the  shell.  If that function is not defined, the shell prints an error
       message and returns an exit status of 127.

       If the search is successful, or if the command  name  contains  one  or
       more  slashes,  the  shell  executes  the  named  program in a separate
       execution environment.  Argument 0 is set to the name  given,  and  the
       remaining  arguments  to the command are set to the arguments given, if
       any.

       If this execution fails because the file is not in  executable  format,
       and  the file is not a directory, it is assumed to be a shell script, a
       file containing shell commands.  A subshell is spawned to  execute  it.
       This  subshell  reinitializes itself, so that the effect is as if a new
       shell had been invoked to handle the script, with  the  exception  that
       the  locations  of  commands  remembered  by the parent (see hash below
       under SHELL BUILTIN COMMANDS) are retained by the child.

       If the program is a file beginning with #!, the remainder of the  first
       line  specifies an interpreter for the program.  The shell executes the
       specified interpreter on operating systems  that  do  not  handle  this
       executable format themselves.  The arguments to the interpreter consist
       of a single optional argument following the  interpreter  name  on  the
       first  line  of  the  program,  followed  by  the  name of the program,
       followed by the command arguments, if any.

COMMAND EXECUTION ENVIRONMENT

       The  shell  has  an  execution  environment,  which  consists  of   the
       following:

       ·      open  files inherited by the shell at invocation, as modified by
              redirections supplied to the exec builtin

       ·      the current working directory as set by cd, pushd, or  popd,  or
              inherited by the shell at invocation

       ·      the  file  creation  mode mask as set by umask or inherited from
              the shell's parent

       ·      current traps set by trap

       ·      shell parameters that are set by variable assignment or with set
              or inherited from the shell's parent in the environment

       ·      shell  functions  defined during execution or inherited from the
              shell's parent in the environment

       ·      options  enabled  at  invocation  (either  by  default  or  with
              command-line arguments) or by set

       ·      options enabled by shopt

       ·      shell aliases defined with alias

       ·      various  process  IDs,  including  those of background jobs, the
              value of $$, and the value of PPID

       When a simple command other than a builtin or shell function is  to  be
       executed,  it  is  invoked  in  a  separate  execution environment that
       consists of the following.  Unless  otherwise  noted,  the  values  are
       inherited from the shell.

       ·      the  shell's  open  files,  plus any modifications and additions
              specified by redirections to the command

       ·      the current working directory

       ·      the file creation mode mask

       ·      shell variables and functions  marked  for  export,  along  with
              variables exported for the command, passed in the environment

       ·      traps caught by the shell are reset to the values inherited from
              the shell's parent, and traps ignored by the shell are ignored

       A command invoked  in  this  separate  environment  cannot  affect  the
       shell's execution environment.

       Command   substitution,   commands   grouped   with   parentheses,  and
       asynchronous commands are invoked in a subshell environment that  is  a
       duplicate  of  the  shell  environment, except that traps caught by the
       shell are reset to the values that the shell inherited from its  parent
       at invocation.  Builtin commands that are invoked as part of a pipeline
       are also executed in a  subshell  environment.   Changes  made  to  the
       subshell environment cannot affect the shell's execution environment.

       Subshells spawned to execute command substitutions inherit the value of
       the -e option from the parent shell.  When  not  in  posix  mode,  bash
       clears the -e option in such subshells.

       If  a  command  is  followed  by a & and job control is not active, the
       default standard input for the command is  the  empty  file  /dev/null.
       Otherwise,  the  invoked  command  inherits the file descriptors of the
       calling shell as modified by redirections.

ENVIRONMENT

       When a program is invoked it is given an array of  strings  called  the
       environment.   This  is  a  list  of  name-value  pairs,  of  the  form
       name=value.

       The shell provides several ways  to  manipulate  the  environment.   On
       invocation, the shell scans its own environment and creates a parameter
       for each name found, automatically  marking  it  for  export  to  child
       processes.   Executed commands inherit the environment.  The export and
       declare -x commands allow parameters and functions to be added  to  and
       deleted  from  the  environment.   If  the  value of a parameter in the
       environment is modified, the new value becomes part of the environment,
       replacing  the  old.  The environment inherited by any executed command
       consists of the  shell's  initial  environment,  whose  values  may  be
       modified  in  the  shell,  less any pairs removed by the unset command,
       plus any additions via the export and declare -x commands.

       The environment for any simple command or  function  may  be  augmented
       temporarily  by  prefixing  it with parameter assignments, as described
       above in PARAMETERS.   These  assignment  statements  affect  only  the
       environment seen by that command.

       If  the  -k option is set (see the set builtin command below), then all
       parameter assignments are placed in the environment for a command,  not
       just those that precede the command name.

       When  bash  invokes  an  external command, the variable _ is set to the
       full filename of  the  command  and  passed  to  that  command  in  its
       environment.

EXIT STATUS

       The  exit  status  of  an executed command is the value returned by the
       waitpid system call or equivalent function.  Exit statuses fall between
       0  and  255, though, as explained below, the shell may use values above
       125 specially.  Exit statuses from shell builtins and compound commands
       are  also limited to this range. Under certain circumstances, the shell
       will use special values to indicate specific failure modes.

       For the shell's purposes, a command which exits with a zero exit status
       has  succeeded.   An exit status of zero indicates success.  A non-zero
       exit status indicates failure.  When a command terminates  on  a  fatal
       signal N, bash uses the value of 128+N as the exit status.

       If  a  command  is  not  found, the child process created to execute it
       returns a status of 127.  If a command is found but is not  executable,
       the return status is 126.

       If a command fails because of an error during expansion or redirection,
       the exit status is greater than zero.

       Shell builtin commands return a status of 0 (true) if  successful,  and
       non-zero  (false)  if an error occurs while they execute.  All builtins
       return an exit status of 2 to indicate incorrect usage.

       Bash itself returns the exit  status  of  the  last  command  executed,
       unless  a  syntax  error occurs, in which case it exits with a non-zero
       value.  See also the exit builtin command below.

SIGNALS

       When bash is interactive, in the  absence  of  any  traps,  it  ignores
       SIGTERM (so that kill 0 does not kill an interactive shell), and SIGINT
       is caught and handled (so that the wait builtin is interruptible).   In
       all  cases,  bash  ignores  SIGQUIT.  If job control is in effect, bash
       ignores SIGTTIN, SIGTTOU, and SIGTSTP.

       Non-builtin commands run by bash have signal handlers set to the values
       inherited  by  the  shell  from its parent.  When job control is not in
       effect, asynchronous commands ignore SIGINT and SIGQUIT in addition  to
       these  inherited  handlers.   Commands  run  as  a  result  of  command
       substitution ignore the keyboard-generated job control signals SIGTTIN,
       SIGTTOU, and SIGTSTP.

       The  shell  exits by default upon receipt of a SIGHUP.  Before exiting,
       an interactive shell  resends  the  SIGHUP  to  all  jobs,  running  or
       stopped.  Stopped jobs are sent SIGCONT to ensure that they receive the
       SIGHUP.  To prevent the shell from sending the signal to  a  particular
       job,  it  should be removed from the jobs table with the disown builtin
       (see SHELL BUILTIN COMMANDS below) or  marked  to  not  receive  SIGHUP
       using disown -h.

       If  the  huponexit  shell  option has been set with shopt, bash sends a
       SIGHUP to all jobs when an interactive login shell exits.

       If bash is waiting for a command to complete and receives a signal  for
       which  a  trap  has  been  set, the trap will not be executed until the
       command completes.  When bash is waiting for  an  asynchronous  command
       via  the  wait  builtin, the reception of a signal for which a trap has
       been set will cause the wait builtin to return immediately with an exit
       status greater than 128, immediately after which the trap is executed.

JOB CONTROL

       Job  control  refers  to  the ability to selectively stop (suspend) the
       execution of processes and continue (resume) their execution at a later
       point.   A  user  typically  employs  this  facility via an interactive
       interface supplied jointly by the operating  system  kernel's  terminal
       driver and bash.

       The  shell  associates  a  job with each pipeline.  It keeps a table of
       currently executing jobs, which may be listed with  the  jobs  command.
       When  bash starts a job asynchronously (in the background), it prints a
       line that looks like:

              [1] 25647

       indicating that this job is job number 1 and that the process ID of the
       last process in the pipeline associated with this job is 25647.  All of
       the processes in a single pipeline are members of the same  job.   Bash
       uses the job abstraction as the basis for job control.

       To  facilitate the implementation of the user interface to job control,
       the operating system maintains the notion of a current terminal process
       group ID.  Members of this process group (processes whose process group
       ID is equal to the current terminal process group ID) receive keyboard-
       generated  signals  such  as SIGINT.  These processes are said to be in
       the foreground.  Background processes are those whose process group  ID
       differs  from  the  terminal's;  such processes are immune to keyboard-
       generated signals.  Only foreground processes are allowed to read  from
       or,  if  the user so specifies with stty tostop, write to the terminal.
       Background processes which attempt to read from  (write  to  when  stty
       tostop  is  in effect) the terminal are sent a SIGTTIN (SIGTTOU) signal
       by the kernel's terminal driver, which,  unless  caught,  suspends  the
       process.

       If  the operating system on which bash is running supports job control,
       bash contains facilities to  use  it.   Typing  the  suspend  character
       (typically  ^Z,  Control-Z)  while  a  process  is  running causes that
       process to be stopped and returns control to bash.  Typing the  delayed
       suspend  character  (typically  ^Y, Control-Y) causes the process to be
       stopped when it attempts to read input from the terminal,  and  control
       to be returned to bash.  The user may then manipulate the state of this
       job, using the bg command to continue it  in  the  background,  the  fg
       command  to  continue it in the foreground, or the kill command to kill
       it.  A ^Z takes effect immediately, and has the additional side  effect
       of causing pending output and typeahead to be discarded.

       There  are  a  number  of  ways  to  refer  to a job in the shell.  The
       character % introduces a job specification (jobspec).  Job number n may
       be  referred to as %n.  A job may also be referred to using a prefix of
       the name used to start it, or using a substring  that  appears  in  its
       command  line.   For  example,  %ce  refers  to a stopped ce job.  If a
       prefix matches more than one job, bash reports an error.   Using  %?ce,
       on  the  other  hand, refers to any job containing the string ce in its
       command line.  If the substring matches more than one job, bash reports
       an  error.   The  symbols  %% and %+ refer to the shell's notion of the
       current job, which is  the  last  job  stopped  while  it  was  in  the
       foreground  or  started  in  the  background.   The previous job may be
       referenced using %-.  If there is only a single job, %+ and %- can both
       be  used to refer to that job.  In output pertaining to jobs (e.g., the
       output of the jobs command), the current job is always flagged  with  a
       +, and the previous job with a -.  A single % (with no accompanying job
       specification) also refers to the current job.

       Simply naming a job can be used to bring it into the foreground: %1  is
       a  synonym  for  ``fg %1'', bringing job 1 from the background into the
       foreground.  Similarly, ``%1 &''  resumes  job  1  in  the  background,
       equivalent to ``bg %1''.

       The  shell  learns immediately whenever a job changes state.  Normally,
       bash waits until it is about to print a prompt before reporting changes
       in  a  job's status so as to not interrupt any other output.  If the -b
       option to the set builtin command is enabled, bash reports such changes
       immediately.   Any  trap  on  SIGCHLD  is  executed for each child that
       exits.

       If an attempt to exit bash is made while jobs are stopped (or,  if  the
       checkjobs  shell  option  has  been  enabled  using  the shopt builtin,
       running), the shell prints a warning message,  and,  if  the  checkjobs
       option is enabled, lists the jobs and their statuses.  The jobs command
       may then be used to inspect their status.  If a second attempt to  exit
       is  made  without  an  intervening  command,  the  shell does not print
       another warning, and any stopped jobs are terminated.

PROMPTING

       When executing interactively, bash displays the primary prompt PS1 when
       it  is  ready  to  read a command, and the secondary prompt PS2 when it
       needs more input to complete  a  command.   Bash  allows  these  prompt
       strings  to  be  customized  by inserting a number of backslash-escaped
       special characters that are decoded as follows:
              \a     an ASCII bell character (07)
              \d     the date in "Weekday Month Date" format (e.g.,  "Tue  May
                     26")
              \D{format}
                     the  format  is  passed  to strftime(3) and the result is
                     inserted into the prompt string; an empty format  results
                     in a locale-specific time representation.  The braces are
                     required
                   an ASCII escape character (033)
              \h     the hostname up to the first `.'
              \H     the hostname
              \j     the number of jobs currently managed by the shell
              \l     the basename of the shell's terminal device name
              
     newline
              
     carriage return
              \s     the name of the shell, the basename of  $0  (the  portion
                     following the final slash)
              	     the current time in 24-hour HH:MM:SS format
              \T     the current time in 12-hour HH:MM:SS format
              \@     the current time in 12-hour am/pm format
              \A     the current time in 24-hour HH:MM format
              \u     the username of the current user
                   the version of bash (e.g., 2.00)
              \V     the release of bash, version + patch level (e.g., 2.00.0)
              \w     the  current  working  directory,  with $HOME abbreviated
                     with a  tilde  (uses  the  value  of  the  PROMPT_DIRTRIM
                     variable)
              \W     the basename of the current working directory, with $HOME
                     abbreviated with a tilde
              \!     the history number of this command
              \#     the command number of this command
              \$     if the effective UID is 0, a #, otherwise a $
              \nnn   the character corresponding to the octal number nnn
              \     a backslash
              \[     begin a sequence of non-printing characters, which  could
                     be  used  to  embed  a terminal control sequence into the
                     prompt
              \]     end a sequence of non-printing characters

       The command number and the history number are  usually  different:  the
       history  number of a command is its position in the history list, which
       may include commands  restored  from  the  history  file  (see  HISTORY
       below),  while  the  command  number is the position in the sequence of
       commands executed during the current shell session.  After  the  string
       is   decoded,   it   is   expanded  via  parameter  expansion,  command
       substitution, arithmetic expansion, and quote removal, subject  to  the
       value  of the promptvars shell option (see the description of the shopt
       command under SHELL BUILTIN COMMANDS below).

READLINE

       This  is  the  library  that  handles  reading  input  when  using   an
       interactive  shell,  unless  the  --noediting  option is given at shell
       invocation.  Line editing is also used when using the -e option to  the
       read  builtin.   By  default,  the line editing commands are similar to
       those of Emacs.  A vi-style line editing interface is  also  available.
       Line  editing  can  be  enabled at any time using the -o emacs or -o vi
       options to the set builtin (see SHELL BUILTIN COMMANDS below).  To turn
       off  line editing after the shell is running, use the +o emacs or +o vi
       options to the set builtin.

   Readline Notation
       In this section, the Emacs-style notation is used to denote keystrokes.
       Control   keys  are  denoted  by  C-key,  e.g.,  C-n  means  Control-N.
       Similarly, meta keys are denoted by M-key, so M-x  means  Meta-X.   (On
       keyboards  without  a meta key, M-x means ESC x, i.e., press the Escape
       key then the x key.  This makes ESC the meta prefix.   The  combination
       M-C-x  means  ESC-Control-x,  or  press  the  Escape  key then hold the
       Control key while pressing the x key.)

       Readline commands may be given numeric arguments, which normally act as
       a  repeat  count.   Sometimes,  however, it is the sign of the argument
       that is significant.  Passing a negative argument  to  a  command  that
       acts  in the forward direction (e.g., kill-line) causes that command to
       act in a backward direction.  Commands whose  behavior  with  arguments
       deviates from this are noted below.

       When  a command is described as killing text, the text deleted is saved
       for possible future retrieval (yanking).  The killed text is saved in a
       kill ring.  Consecutive kills cause the text to be accumulated into one
       unit, which can be yanked all at once.  Commands which do not kill text
       separate the chunks of text on the kill ring.

   Readline Initialization
       Readline  is  customized  by putting commands in an initialization file
       (the inputrc file).  The name of this file is taken from the  value  of
       the  INPUTRC  variable.   If  that  variable  is  unset, the default is
       ~/.inputrc.  When a program which uses the readline library starts  up,
       the initialization file is read, and the key bindings and variables are
       set.  There are only a few basic constructs  allowed  in  the  readline
       initialization  file.  Blank lines are ignored.  Lines beginning with a
       #  are  comments.   Lines  beginning  with  a  $  indicate  conditional
       constructs.  Other lines denote key bindings and variable settings.

       The  default  key-bindings  may be changed with an inputrc file.  Other
       programs that use this library may add their own commands and bindings.

       For example, placing

              M-Control-u: universal-argument
       or
              C-Meta-u: universal-argument
       into  the  inputrc  would  make  M-C-u  execute  the  readline  command
       universal-argument.

       The  following  symbolic  character  names are recognized: RUBOUT, DEL,
       ESC, LFD, NEWLINE, RET, RETURN, SPC, SPACE, and TAB.

       In addition to command names, readline allows keys to  be  bound  to  a
       string that is inserted when the key is pressed (a macro).

   Readline Key Bindings
       The  syntax for controlling key bindings in the inputrc file is simple.
       All that is required is the name of the command or the text of a  macro
       and  a  key  sequence  to  which  it  should  be bound. The name may be
       specified in one of two ways: as a symbolic  key  name,  possibly  with
       Meta- or Control- prefixes, or as a key sequence.

       When using the form keyname:function-name or macro, keyname is the name
       of a key spelled out in English.  For example:

              Control-u: universal-argument
              Meta-Rubout: backward-kill-word
              Control-o: "> output"

       In the above example, C-u is bound to the function  universal-argument,
       M-DEL  is bound to the function backward-kill-word, and C-o is bound to
       run the macro expressed on the right hand side (that is, to insert  the
       text ``> output'' into the line).

       In  the  second  form,  "keyseq":function-name or macro, keyseq differs
       from keyname above in that strings denoting an entire key sequence  may
       be  specified  by  placing the sequence within double quotes.  Some GNU
       Emacs style key escapes can be used, as in the following  example,  but
       the symbolic character names are not recognized.

              "\C-u": universal-argument
              "\C-x\C-r": re-read-init-file
              "[11~": "Function Key 1"

       In this example, C-u is again bound to the function universal-argument.
       C-x C-r is bound to the function re-read-init-file, and ESC [ 1 1 ~  is
       bound to insert the text ``Function Key 1''.

       The full set of GNU Emacs style escape sequences is
              \C-    control prefix
              \M-    meta prefix
                   an escape character
              \     backslash
              \"     literal "
              \'     literal '

       In  addition  to  the GNU Emacs style escape sequences, a second set of
       backslash escapes is available:
              \a     alert (bell)
              \b     backspace
              \d     delete
                   form feed
              
     newline
              
     carriage return
              	     horizontal tab
                   vertical tab
              \nnn   the eight-bit character whose value is  the  octal  value
                     nnn (one to three digits)
              \xHH   the  eight-bit  character  whose value is the hexadecimal
                     value HH (one or two hex digits)

       When entering the text of a macro, single or double quotes must be used
       to  indicate  a  macro  definition.   Unquoted  text is assumed to be a
       function name.  In the macro  body,  the  backslash  escapes  described
       above  are  expanded.   Backslash will quote any other character in the
       macro text, including " and '.

       Bash allows the current  readline  key  bindings  to  be  displayed  or
       modified  with  the  bind  builtin  command.   The  editing mode may be
       switched during interactive use by using  the  -o  option  to  the  set
       builtin command (see SHELL BUILTIN COMMANDS below).

   Readline Variables
       Readline  has  variables  that  can  be  used  to further customize its
       behavior.  A variable may be set in the inputrc file with  a  statement
       of the form

              set variable-name value

       Except  where  noted,  readline variables can take the values On or Off
       (without regard to case).  Unrecognized  variable  names  are  ignored.
       When  a  variable  value  is  read,  empty  or null values, "on" (case-
       insensitive), and "1" are equivalent  to  On.   All  other  values  are
       equivalent to Off.  The variables and their default values are:

       bell-style (audible)
              Controls  what  happens when readline wants to ring the terminal
              bell.  If set to none, readline never rings the bell.  If set to
              visible,  readline  uses a visible bell if one is available.  If
              set to audible, readline attempts to ring the terminal's bell.
       bind-tty-special-chars (On)
              If set to On, readline attempts to bind the  control  characters
              treated  specially  by  the  kernel's  terminal  driver to their
              readline equivalents.
       colored-stats (Off)
              If set to  On,  readline  displays  possible  completions  using
              different  colors  to  indicate  their  file  type.   The  color
              definitions  are  taken  from  the  value   of   the   LS_COLORS
              environment variable.
       comment-begin (``#'')
              The  string  that  is  inserted when the readline insert-comment
              command is executed.  This command is bound to M-# in emacs mode
              and to # in vi command mode.
       completion-ignore-case (Off)
              If set to On, readline performs filename matching and completion
              in a case-insensitive fashion.
       completion-prefix-display-length (0)
              The length in characters of the  common  prefix  of  a  list  of
              possible  completions  that  is  displayed without modification.
              When set to a value greater than zero,  common  prefixes  longer
              than  this  value  are replaced with an ellipsis when displaying
              possible completions.
       completion-query-items (100)
              This determines when the  user  is  queried  about  viewing  the
              number    of    possible    completions    generated    by   the
              possible-completions command.  It may  be  set  to  any  integer
              value  greater than or equal to zero.  If the number of possible
              completions is greater than  or  equal  to  the  value  of  this
              variable,  the  user  is  asked whether or not he wishes to view
              them; otherwise they are simply listed on the terminal.
       convert-meta (On)
              If set to On, readline will convert characters with  the  eighth
              bit set to an ASCII key sequence by stripping the eighth bit and
              prefixing an escape character (in effect, using  escape  as  the
              meta prefix).
       disable-completion (Off)
              If set to On, readline will inhibit word completion.  Completion
              characters will be inserted into the line as if  they  had  been
              mapped to self-insert.
       editing-mode (emacs)
              Controls  whether  readline  begins  with  a set of key bindings
              similar to Emacs or vi.  editing-mode can be set to either emacs
              or vi.
       echo-control-characters (On)
              When  set to On, on operating systems that indicate they support
              it, readline  echoes  a  character  corresponding  to  a  signal
              generated from the keyboard.
       enable-keypad (Off)
              When  set  to  On,  readline  will try to enable the application
              keypad when it is called.  Some systems need this to enable  the
              arrow keys.
       enable-meta-key (On)
              When  set  to  On, readline will try to enable any meta modifier
              key the terminal claims to support when it is called.   On  many
              terminals, the meta key is used to send eight-bit characters.
       expand-tilde (Off)
              If  set  to  On,  tilde  expansion  is  performed  when readline
              attempts word completion.
       history-preserve-point (Off)
              If set to On, the history code attempts to place  point  at  the
              same  location  on  each  history  line retrieved with previous-
              history or next-history.
       history-size (0)
              Set the maximum number of history entries saved in  the  history
              list.   If set to zero, any existing history entries are deleted
              and no new entries are saved.  If set to a value less than zero,
              the  number  of history entries is not limited.  By default, the
              number of history entries is not limited.
       horizontal-scroll-mode (Off)
              When set to On, makes readline use a single  line  for  display,
              scrolling the input horizontally on a single screen line when it
              becomes longer than the screen width rather than wrapping  to  a
              new line.
       input-meta (Off)
              If  set to On, readline will enable eight-bit input (that is, it
              will not strip the high  bit  from  the  characters  it  reads),
              regardless of what the terminal claims it can support.  The name
              meta-flag is a synonym for this variable.
       isearch-terminators (``C-[C-J'')
              The string of characters that should  terminate  an  incremental
              search   without  subsequently  executing  the  character  as  a
              command.  If this variable has  not  been  given  a  value,  the
              characters ESC and C-J will terminate an incremental search.
       keymap (emacs)
              Set  the current readline keymap.  The set of valid keymap names
              is   emacs,   emacs-standard,   emacs-meta,   emacs-ctlx,    vi,
              vi-command,  and  vi-insert.   vi  is  equivalent to vi-command;
              emacs is equivalent to emacs-standard.   The  default  value  is
              emacs;  the  value  of  editing-mode  also  affects  the default
              keymap.
       keyseq-timeout (500)
              Specifies the duration readline will wait for a  character  when
              reading  an ambiguous key sequence (one that can form a complete
              key sequence using the input read so far, or can take additional
              input  to  complete  a  longer  key  sequence).   If no input is
              received within the timeout, readline will use the  shorter  but
              complete  key sequence.  The value is specified in milliseconds,
              so a value of 1000 means that readline will wait one second  for
              additional  input.  If this variable is set to a value less than
              or equal to zero, or to a non-numeric value, readline will  wait
              until  another  key  is  pressed to decide which key sequence to
              complete.
       mark-directories (On)
              If set to On, completed directory names have a slash appended.
       mark-modified-lines (Off)
              If set  to  On,  history  lines  that  have  been  modified  are
              displayed with a preceding asterisk (*).
       mark-symlinked-directories (Off)
              If  set  to  On,  completed  names  which  are symbolic links to
              directories have a slash  appended  (subject  to  the  value  of
              mark-directories).
       match-hidden-files (On)
              This  variable,  when  set to On, causes readline to match files
              whose names begin with a  `.'  (hidden  files)  when  performing
              filename  completion.   If  set  to Off, the leading `.' must be
              supplied by the user in the filename to be completed.
       menu-complete-display-prefix (Off)
              If set to On, menu completion displays the common prefix of  the
              list of possible completions (which may be empty) before cycling
              through the list.
       output-meta (Off)
              If set to On, readline will display characters with  the  eighth
              bit set directly rather than as a meta-prefixed escape sequence.
       page-completions (On)
              If  set  to  On,  readline  uses  an internal more-like pager to
              display a screenful of possible completions at a time.
       print-completions-horizontally (Off)
              If set to On, readline will  display  completions  with  matches
              sorted  horizontally in alphabetical order, rather than down the
              screen.
       revert-all-at-newline (Off)
              If set to On, readline will undo all changes  to  history  lines
              before  returning  when  accept-line  is  executed.  By default,
              history lines may be modified and retain individual  undo  lists
              across calls to readline.
       show-all-if-ambiguous (Off)
              This  alters  the  default behavior of the completion functions.
              If set to On, words which have more than one possible completion
              cause  the  matches  to be listed immediately instead of ringing
              the bell.
       show-all-if-unmodified (Off)
              This alters the default behavior of the completion functions  in
              a fashion similar to show-all-if-ambiguous.  If set to On, words
              which  have  more  than  one  possible  completion  without  any
              possible  partial  completion  (the  possible  completions don't
              share  a  common  prefix)  cause  the  matches  to   be   listed
              immediately instead of ringing the bell.
       show-mode-in-prompt (Off)
              If  set  to  On,  add a character to the beginning of the prompt
              indicating the editing mode: emacs (@), vi  command  (:)  or  vi
              insertion (+).
       skip-completed-text (Off)
              If  set  to On, this alters the default completion behavior when
              inserting a single match into the line.  It's only  active  when
              performing  completion  in  the  middle  of a word.  If enabled,
              readline does not insert characters  from  the  completion  that
              match  characters  after  point  in the word being completed, so
              portions of the word following the cursor are not duplicated.
       visible-stats (Off)
              If set to On, a character denoting a file's type as reported  by
              stat(2)  is  appended  to  the  filename  when  listing possible
              completions.

   Readline Conditional Constructs
       Readline implements a facility similar in  spirit  to  the  conditional
       compilation  features  of  the C preprocessor which allows key bindings
       and variable settings to be performed as the result  of  tests.   There
       are four parser directives used.

       $if    The  $if  construct  allows  bindings  to  be  made based on the
              editing mode, the terminal being used, or the application  using
              readline.   The text of the test extends to the end of the line;
              no characters are required to isolate it.

              mode   The mode= form of the  $if  directive  is  used  to  test
                     whether  readline  is  in  emacs or vi mode.  This may be
                     used in conjunction with  the  set  keymap  command,  for
                     instance,  to  set  bindings  in  the  emacs-standard and
                     emacs-ctlx keymaps only if readline is  starting  out  in
                     emacs mode.

              term   The  term=  form may be used to include terminal-specific
                     key bindings, perhaps to bind the key sequences output by
                     the terminal's function keys.  The word on the right side
                     of the = is tested against the  both  full  name  of  the
                     terminal  and the portion of the terminal name before the
                     first -.  This allows sun to match both sun and  sun-cmd,
                     for instance.

              application
                     The application construct is used to include application-
                     specific  settings.   Each  program  using  the  readline
                     library  sets the application name, and an initialization
                     file can test for a particular value.  This could be used
                     to  bind key sequences to functions useful for a specific
                     program.  For instance, the following command adds a  key
                     sequence  that  quotes  the  current  or previous word in
                     bash:

                     $if Bash
                     # Quote the current or previous word
                     "\C-xq": "b\"f\""
                     $endif

       $endif This command, as seen in the previous example, terminates an $if
              command.

       $else  Commands in this branch of the $if directive are executed if the
              test fails.

       $include
              This directive takes a single filename as an argument and  reads
              commands   and  bindings  from  that  file.   For  example,  the
              following directive would read /etc/inputrc:

              $include  /etc/inputrc

   Searching
       Readline provides commands for searching through  the  command  history
       (see HISTORY below) for lines containing a specified string.  There are
       two search modes: incremental and non-incremental.

       Incremental searches begin before the  user  has  finished  typing  the
       search  string.   As  each  character  of  the  search string is typed,
       readline displays the next entry from the history matching  the  string
       typed  so  far.  An incremental search requires only as many characters
       as needed to find the desired history entry.  The characters present in
       the  value of the isearch-terminators variable are used to terminate an
       incremental search.  If that variable has not been assigned a value the
       Escape  and  Control-J characters will terminate an incremental search.
       Control-G will abort an incremental search  and  restore  the  original
       line.   When the search is terminated, the history entry containing the
       search string becomes the current line.

       To find other matching entries in the history list, type  Control-S  or
       Control-R  as appropriate.  This will search backward or forward in the
       history for the next entry matching the search  string  typed  so  far.
       Any  other  key sequence bound to a readline command will terminate the
       search  and  execute  that  command.   For  instance,  a  newline  will
       terminate the search and accept the line, thereby executing the command
       from the history list.

       Readline remembers the last incremental search string.  If two Control-
       Rs  are  typed without any intervening characters defining a new search
       string, any remembered search string is used.

       Non-incremental searches read the entire search string before  starting
       to  search  for matching history lines.  The search string may be typed
       by the user or be part of the contents of the current line.

   Readline Command Names
       The following is a list of the names of the commands  and  the  default
       key  sequences  to  which  they  are  bound.   Command names without an
       accompanying key sequence are unbound by  default.   In  the  following
       descriptions,  point  refers  to  the current cursor position, and mark
       refers to a cursor position saved by the set-mark  command.   The  text
       between the point and mark is referred to as the region.

   Commands for Moving
       beginning-of-line (C-a)
              Move to the start of the current line.
       end-of-line (C-e)
              Move to the end of the line.
       forward-char (C-f)
              Move forward a character.
       backward-char (C-b)
              Move back a character.
       forward-word (M-f)
              Move forward to the end of the next word.  Words are composed of
              alphanumeric characters (letters and digits).
       backward-word (M-b)
              Move back to the start of the current or previous  word.   Words
              are composed of alphanumeric characters (letters and digits).
       shell-forward-word
              Move  forward  to the end of the next word.  Words are delimited
              by non-quoted shell metacharacters.
       shell-backward-word
              Move back to the start of the current or previous  word.   Words
              are delimited by non-quoted shell metacharacters.
       clear-screen (C-l)
              Clear  the  screen  leaving  the  current line at the top of the
              screen.  With an argument,  refresh  the  current  line  without
              clearing the screen.
       redraw-current-line
              Refresh the current line.

   Commands for Manipulating the History
       accept-line (Newline, Return)
              Accept the line regardless of where the cursor is.  If this line
              is non-empty, add it to the history list according to the  state
              of  the HISTCONTROL variable.  If the line is a modified history
              line, then restore the history line to its original state.
       previous-history (C-p)
              Fetch the previous command from the history list, moving back in
              the list.
       next-history (C-n)
              Fetch  the next command from the history list, moving forward in
              the list.
       beginning-of-history (M-<)
              Move to the first line in the history.
       end-of-history (M->)
              Move to the end of the input history, i.e., the  line  currently
              being entered.
       reverse-search-history (C-r)
              Search  backward  starting  at  the current line and moving `up'
              through the  history  as  necessary.   This  is  an  incremental
              search.
       forward-search-history (C-s)
              Search  forward  starting  at the current line and moving `down'
              through the  history  as  necessary.   This  is  an  incremental
              search.
       non-incremental-reverse-search-history (M-p)
              Search backward through the history starting at the current line
              using a non-incremental search for  a  string  supplied  by  the
              user.
       non-incremental-forward-search-history (M-n)
              Search  forward  through  the  history  using  a non-incremental
              search for a string supplied by the user.
       history-search-forward
              Search forward through the history for the string of  characters
              between  the start of the current line and the point.  This is a
              non-incremental search.
       history-search-backward
              Search backward through the history for the string of characters
              between  the start of the current line and the point.  This is a
              non-incremental search.
       yank-nth-arg (M-C-y)
              Insert the first argument to the previous command  (usually  the
              second word on the previous line) at point.  With an argument n,
              insert the nth word from the previous command (the words in  the
              previous  command  begin  with  word  0).   A  negative argument
              inserts the nth word from the end of the previous command.  Once
              the  argument n is computed, the argument is extracted as if the
              "!n" history expansion had been specified.
       yank-last-arg (M-., M-_)
              Insert the last argument to the previous command (the last  word
              of the previous history entry).  With a numeric argument, behave
              exactly like yank-nth-arg.  Successive  calls  to  yank-last-arg
              move  back through the history list, inserting the last word (or
              the word specified by the argument to the first  call)  of  each
              line in turn.  Any numeric argument supplied to these successive
              calls determines the direction to move through the  history.   A
              negative  argument  switches  the  direction through the history
              (back or forward).  The history expansion facilities are used to
              extract the last word, as if the "!$" history expansion had been
              specified.
       shell-expand-line (M-C-e)
              Expand the line as the shell  does.   This  performs  alias  and
              history  expansion  as well as all of the shell word expansions.
              See  HISTORY  EXPANSION  below  for  a  description  of  history
              expansion.
       history-expand-line (M-^)
              Perform  history  expansion  on  the  current line.  See HISTORY
              EXPANSION below for a description of history expansion.
       magic-space
              Perform history expansion on  the  current  line  and  insert  a
              space.  See HISTORY EXPANSION below for a description of history
              expansion.
       alias-expand-line
              Perform alias expansion on the current line.  See ALIASES  above
              for a description of alias expansion.
       history-and-alias-expand-line
              Perform history and alias expansion on the current line.
       insert-last-argument (M-., M-_)
              A synonym for yank-last-arg.
       operate-and-get-next (C-o)
              Accept  the  current  line for execution and fetch the next line
              relative to the current line from the history for editing.   Any
              argument is ignored.
       edit-and-execute-command (C-xC-e)
              Invoke  an  editor  on the current command line, and execute the
              result as shell commands.   Bash  attempts  to  invoke  $VISUAL,
              $EDITOR, and emacs as the editor, in that order.

   Commands for Changing Text
       end-of-file (usually C-d)
              The  character  indicating  end-of-file  as set, for example, by
              ``stty''.   If  this  character  is  read  when  there  are   no
              characters  on  the  line,  and point is at the beginning of the
              line, Readline interprets it as the end  of  input  and  returns
              EOF.
       delete-char (C-d)
              Delete the character at point.  If this function is bound to the
              same character as the tty EOF character, as C-d commonly is, see
              above for the effects.
       backward-delete-char (Rubout)
              Delete  the  character  behind the cursor.  When given a numeric
              argument, save the deleted text on the kill ring.
       forward-backward-delete-char
              Delete the character under the cursor, unless the cursor  is  at
              the  end  of  the  line,  in which case the character behind the
              cursor is deleted.
       quoted-insert (C-q, C-v)
              Add the next character typed to the line verbatim.  This is  how
              to insert characters like C-q, for example.
       tab-insert (C-v TAB)
              Insert a tab character.
       self-insert (a, b, A, 1, !, ...)
              Insert the character typed.
       transpose-chars (C-t)
              Drag  the  character  before point forward over the character at
              point, moving point forward as well.  If point is at the end  of
              the  line, then this transposes the two characters before point.
              Negative arguments have no effect.
       transpose-words (M-t)
              Drag the word before point past the  word  after  point,  moving
              point  over  that  word  as well.  If point is at the end of the
              line, this transposes the last two words on the line.
       upcase-word (M-u)
              Uppercase the current (or  following)  word.   With  a  negative
              argument, uppercase the previous word, but do not move point.
       downcase-word (M-l)
              Lowercase  the  current  (or  following)  word.  With a negative
              argument, lowercase the previous word, but do not move point.
       capitalize-word (M-c)
              Capitalize the current (or following)  word.   With  a  negative
              argument, capitalize the previous word, but do not move point.
       overwrite-mode
              Toggle  overwrite  mode.   With  an  explicit  positive  numeric
              argument, switches to overwrite mode.   With  an  explicit  non-
              positive  numeric  argument,  switches  to  insert  mode.   This
              command  affects  only  emacs  mode;  vi  mode  does   overwrite
              differently.  Each call to readline() starts in insert mode.  In
              overwrite mode, characters bound to self-insert replace the text
              at  point rather than pushing the text to the right.  Characters
              bound to backward-delete-char replace the character before point
              with a space.  By default, this command is unbound.

   Killing and Yanking
       kill-line (C-k)
              Kill the text from point to the end of the line.
       backward-kill-line (C-x Rubout)
              Kill backward to the beginning of the line.
       unix-line-discard (C-u)
              Kill  backward  from  point  to  the beginning of the line.  The
              killed text is saved on the kill-ring.
       kill-whole-line
              Kill all characters on the current line, no matter  where  point
              is.
       kill-word (M-d)
              Kill  from  point  to the end of the current word, or if between
              words, to the end of the next word.   Word  boundaries  are  the
              same as those used by forward-word.
       backward-kill-word (M-Rubout)
              Kill  the  word  behind  point.  Word boundaries are the same as
              those used by backward-word.
       shell-kill-word (M-d)
              Kill from point to the end of the current word,  or  if  between
              words,  to  the  end  of the next word.  Word boundaries are the
              same as those used by shell-forward-word.
       shell-backward-kill-word (M-Rubout)
              Kill the word behind point.  Word boundaries  are  the  same  as
              those used by shell-backward-word.
       unix-word-rubout (C-w)
              Kill  the  word  behind  point,  using  white  space  as  a word
              boundary.  The killed text is saved on the kill-ring.
       unix-filename-rubout
              Kill the word behind point, using  white  space  and  the  slash
              character  as  the word boundaries.  The killed text is saved on
              the kill-ring.
       delete-horizontal-space (M-\)
              Delete all spaces and tabs around point.
       kill-region
              Kill the text in the current region.
       copy-region-as-kill
              Copy the text in the region to the kill buffer.
       copy-backward-word
              Copy the word  before  point  to  the  kill  buffer.   The  word
              boundaries are the same as backward-word.
       copy-forward-word
              Copy  the  word  following  point  to the kill buffer.  The word
              boundaries are the same as forward-word.
       yank (C-y)
              Yank the top of the kill ring into the buffer at point.
       yank-pop (M-y)
              Rotate the  kill  ring,  and  yank  the  new  top.   Only  works
              following yank or yank-pop.

   Numeric Arguments
       digit-argument (M-0, M-1, ..., M--)
              Add  this digit to the argument already accumulating, or start a
              new argument.  M-- starts a negative argument.
       universal-argument
              This is another way to specify an argument.  If this command  is
              followed  by one or more digits, optionally with a leading minus
              sign, those digits define  the  argument.   If  the  command  is
              followed  by digits, executing universal-argument again ends the
              numeric argument, but is otherwise ignored.  As a special  case,
              if  this  command is immediately followed by a character that is
              neither a digit or minus sign, the argument count for  the  next
              command  is multiplied by four.  The argument count is initially
              one, so  executing  this  function  the  first  time  makes  the
              argument  count  four,  a  second  time makes the argument count
              sixteen, and so on.

   Completing
       complete (TAB)
              Attempt to perform completion on the text  before  point.   Bash
              attempts completion treating the text as a variable (if the text
              begins with $), username (if the text begins with  ~),  hostname
              (if  the  text begins with @), or command (including aliases and
              functions) in turn.  If none of these produces a match, filename
              completion is attempted.
       possible-completions (M-?)
              List the possible completions of the text before point.
       insert-completions (M-*)
              Insert  all completions of the text before point that would have
              been generated by possible-completions.
       menu-complete
              Similar to complete, but replaces the word to be completed  with
              a  single match from the list of possible completions.  Repeated
              execution of menu-complete steps through the  list  of  possible
              completions,  inserting  each  match in turn.  At the end of the
              list of completions, the bell is rung (subject to the setting of
              bell-style) and the original text is restored.  An argument of n
              moves n positions forward in the list  of  matches;  a  negative
              argument  may  be  used to move backward through the list.  This
              command is intended to be  bound  to  TAB,  but  is  unbound  by
              default.
       menu-complete-backward
              Identical  to menu-complete, but moves backward through the list
              of possible completions, as if menu-complete had  been  given  a
              negative argument.  This command is unbound by default.
       delete-char-or-list
              Deletes  the  character under the cursor if not at the beginning
              or end of the line (like delete-char).  If at  the  end  of  the
              line, behaves identically to possible-completions.  This command
              is unbound by default.
       complete-filename (M-/)
              Attempt filename completion on the text before point.
       possible-filename-completions (C-x /)
              List the possible completions of the text before point, treating
              it as a filename.
       complete-username (M-~)
              Attempt  completion  on  the text before point, treating it as a
              username.
       possible-username-completions (C-x ~)
              List the possible completions of the text before point, treating
              it as a username.
       complete-variable (M-$)
              Attempt  completion  on  the text before point, treating it as a
              shell variable.
       possible-variable-completions (C-x $)
              List the possible completions of the text before point, treating
              it as a shell variable.
       complete-hostname (M-@)
              Attempt  completion  on  the text before point, treating it as a
              hostname.
       possible-hostname-completions (C-x @)
              List the possible completions of the text before point, treating
              it as a hostname.
       complete-command (M-!)
              Attempt  completion  on  the text before point, treating it as a
              command name.  Command completion attempts  to  match  the  text
              against   aliases,   reserved   words,  shell  functions,  shell
              builtins, and finally executable filenames, in that order.
       possible-command-completions (C-x !)
              List the possible completions of the text before point, treating
              it as a command name.
       dynamic-complete-history (M-TAB)
              Attempt  completion on the text before point, comparing the text
              against lines from the  history  list  for  possible  completion
              matches.
       dabbrev-expand
              Attempt  menu completion on the text before point, comparing the
              text against lines from the history list for possible completion
              matches.
       complete-into-braces (M-{)
              Perform  filename  completion  and  insert  the list of possible
              completions enclosed within braces so the list is  available  to
              the shell (see Brace Expansion above).

   Keyboard Macros
       start-kbd-macro (C-x ()
              Begin  saving  the  characters  typed  into the current keyboard
              macro.
       end-kbd-macro (C-x ))
              Stop saving the characters typed into the current keyboard macro
              and store the definition.
       call-last-kbd-macro (C-x e)
              Re-execute  the  last  keyboard  macro  defined,  by  making the
              characters in the macro appear as if typed at the keyboard.
       print-last-kbd-macro ()
              Print the last keyboard macro defined in a format  suitable  for
              the inputrc file.

   Miscellaneous
       re-read-init-file (C-x C-r)
              Read  in  the  contents of the inputrc file, and incorporate any
              bindings or variable assignments found there.
       abort (C-g)
              Abort the current editing command and ring the  terminal's  bell
              (subject to the setting of bell-style).
       do-uppercase-version (M-a, M-b, M-x, ...)
              If  the  metafied character x is lowercase, run the command that
              is bound to the corresponding uppercase character.
       prefix-meta (ESC)
              Metafy the next character typed.  ESC f is equivalent to Meta-f.
       undo (C-_, C-x C-u)
              Incremental undo, separately remembered for each line.
       revert-line (M-r)
              Undo all changes made to this line.  This is like executing  the
              undo  command  enough  times  to  return the line to its initial
              state.
       tilde-expand (M-&)
              Perform tilde expansion on the current word.
       set-mark (C-@, M-<space>)
              Set the mark to the point.  If a numeric argument  is  supplied,
              the mark is set to that position.
       exchange-point-and-mark (C-x C-x)
              Swap  the  point  with the mark.  The current cursor position is
              set to the saved position, and the old cursor position is  saved
              as the mark.
       character-search (C-])
              A character is read and point is moved to the next occurrence of
              that  character.   A  negative  count  searches   for   previous
              occurrences.
       character-search-backward (M-C-])
              A  character  is  read  and  point  is  moved  to  the  previous
              occurrence of that character.  A  negative  count  searches  for
              subsequent occurrences.
       skip-csi-sequence
              Read  enough  characters to consume a multi-key sequence such as
              those defined for keys like Home and End.  Such sequences  begin
              with a Control Sequence Indicator (CSI), usually ESC-[.  If this
              sequence is bound to "\[", keys producing  such  sequences  will
              have  no  effect  unless explicitly bound to a readline command,
              instead of inserting stray characters into the  editing  buffer.
              This is unbound by default, but usually bound to ESC-[.
       insert-comment (M-#)
              Without   a   numeric   argument,  the  value  of  the  readline
              comment-begin variable is  inserted  at  the  beginning  of  the
              current  line.   If a numeric argument is supplied, this command
              acts as a toggle:  if the characters at  the  beginning  of  the
              line  do  not  match  the  value  of comment-begin, the value is
              inserted, otherwise the characters in comment-begin are  deleted
              from  the  beginning  of  the line.  In either case, the line is
              accepted as if a newline had been typed.  The default  value  of
              comment-begin  causes  this  command  to make the current line a
              shell  comment.   If  a  numeric  argument  causes  the  comment
              character to be removed, the line will be executed by the shell.
       glob-complete-word (M-g)
              The  word  before  point  is  treated  as a pattern for pathname
              expansion, with an asterisk implicitly appended.   This  pattern
              is  used  to  generate a list of matching filenames for possible
              completions.
       glob-expand-word (C-x *)
              The word before point is  treated  as  a  pattern  for  pathname
              expansion,  and  the  list  of  matching  filenames is inserted,
              replacing the word.  If  a  numeric  argument  is  supplied,  an
              asterisk is appended before pathname expansion.
       glob-list-expansions (C-x g)
              The  list  of  expansions  that  would  have  been  generated by
              glob-expand-word is displayed, and the line is  redrawn.   If  a
              numeric  argument  is  supplied,  an asterisk is appended before
              pathname expansion.
       dump-functions
              Print all of  the  functions  and  their  key  bindings  to  the
              readline  output stream.  If a numeric argument is supplied, the
              output is formatted in such a way that it can be made part of an
              inputrc file.
       dump-variables
              Print all of the settable readline variables and their values to
              the readline output stream.  If a numeric argument is  supplied,
              the  output  is formatted in such a way that it can be made part
              of an inputrc file.
       dump-macros
              Print all of the readline key sequences bound to macros and  the
              strings  they  output.   If  a numeric argument is supplied, the
              output is formatted in such a way that it can be made part of an
              inputrc file.
       display-shell-version (C-x C-v)
              Display version information about the current instance of bash.

   Programmable Completion
       When  word  completion  is  attempted  for an argument to a command for
       which a completion specification (a compspec) has  been  defined  using
       the   complete   builtin   (see  SHELL  BUILTIN  COMMANDS  below),  the
       programmable completion facilities are invoked.

       First, the command name is identified.  If  the  command  word  is  the
       empty  string (completion attempted at the beginning of an empty line),
       any compspec defined with the -E option to  complete  is  used.   If  a
       compspec  has  been  defined  for that command, the compspec is used to
       generate the list of possible completions for the word.  If the command
       word  is  a full pathname, a compspec for the full pathname is searched
       for first.  If no compspec is found for the full pathname,  an  attempt
       is  made  to find a compspec for the portion following the final slash.
       If those searches do not result in a  compspec,  any  compspec  defined
       with the -D option to complete is used as the default.

       Once  a  compspec  has  been  found, it is used to generate the list of
       matching  words.   If  a  compspec  is  not  found,  the  default  bash
       completion as described above under Completing is performed.

       First,  the  actions  specified by the compspec are used.  Only matches
       which are prefixed by the word being completed are returned.  When  the
       -f  or -d option is used for filename or directory name completion, the
       shell variable FIGNORE is used to filter the matches.

       Any completions specified by a pathname expansion  pattern  to  the  -G
       option are generated next.  The words generated by the pattern need not
       match the word being completed.  The GLOBIGNORE shell variable  is  not
       used to filter the matches, but the FIGNORE variable is used.

       Next,  the  string  specified  as  the  argument  to  the  -W option is
       considered.  The string is first split using the characters in the  IFS
       special  variable  as delimiters.  Shell quoting is honored.  Each word
       is then expanded using brace expansion, tilde expansion, parameter  and
       variable  expansion, command substitution, and arithmetic expansion, as
       described above under EXPANSION.  The results are split using the rules
       described above under Word Splitting.  The results of the expansion are
       prefix-matched against the word being completed, and the matching words
       become the possible completions.

       After  these matches have been generated, any shell function or command
       specified with the -F and -C options is invoked.  When the  command  or
       function is invoked, the COMP_LINE, COMP_POINT, COMP_KEY, and COMP_TYPE
       variables are assigned values as described above under Shell Variables.
       If  a  shell  function  is being invoked, the COMP_WORDS and COMP_CWORD
       variables are also set.  When the function or command is  invoked,  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.  No filtering of  the  generated
       completions against the word being completed is performed; the function
       or command has complete freedom in generating the matches.

       Any function specified with -F is invoked first.  The function may  use
       any  of  the  shell facilities, including the compgen builtin described
       below, to generate the matches.  It must put the  possible  completions
       in the COMPREPLY array variable, one per array element.

       Next,  any  command  specified  with  the  -C  option  is invoked in an
       environment equivalent to command substitution.  It should print a list
       of completions, one per line, to the standard output.  Backslash may be
       used to escape a newline, if necessary.

       After all  of  the  possible  completions  are  generated,  any  filter
       specified  with  the -X option is applied to the list.  The filter is a
       pattern as used for pathname expansion; a & in the pattern is  replaced
       with  the text of the word being completed.  A literal & may be escaped
       with a backslash; the backslash is removed before attempting  a  match.
       Any  completion that matches the pattern will be removed from the list.
       A leading ! negates the  pattern;  in  this  case  any  completion  not
       matching the pattern will be removed.

       Finally, any prefix and suffix specified with the -P and -S options are
       added to each member of the completion list, and the result is returned
       to the readline completion code as the list of possible completions.

       If  the previously-applied actions do not generate any matches, and the
       -o dirnames option was supplied  to  complete  when  the  compspec  was
       defined, directory name completion is attempted.

       If  the  -o  plusdirs option was supplied to complete when the compspec
       was defined, directory name completion is attempted and any matches are
       added to the results of the other actions.

       By  default,  if a compspec is found, whatever it generates is returned
       to the completion code as the full set of  possible  completions.   The
       default bash completions are not attempted, and the readline default of
       filename completion is disabled.  If  the  -o  bashdefault  option  was
       supplied  to  complete  when the compspec was defined, the bash default
       completions are attempted if the compspec generates no matches.  If the
       -o  default  option  was  supplied  to  complete  when the compspec was
       defined,  readline's  default  completion  will  be  performed  if  the
       compspec  (and, if attempted, the default bash completions) generate no
       matches.

       When a compspec indicates that directory name  completion  is  desired,
       the  programmable completion functions force readline to append a slash
       to completed names which are symbolic links to directories, subject  to
       the  value of the mark-directories readline variable, regardless of the
       setting of the mark-symlinked-directories readline variable.

       There is some support for dynamically modifying completions.   This  is
       most  useful  when  used  in  combination  with  a  default  completion
       specified with complete -D.  It's possible for shell functions executed
       as completion handlers to indicate that completion should be retried by
       returning an exit status of 124.  If a shell function returns 124,  and
       changes the compspec associated with the command on which completion is
       being attempted (supplied as the first argument when  the  function  is
       executed), programmable completion restarts from the beginning, with an
       attempt to find a new compspec for that command.  This allows a set  of
       completions  to be built dynamically as completion is attempted, rather
       than being loaded all at once.

       For instance, assuming that there is a library of compspecs, each  kept
       in  a  file  corresponding  to  the  name of the command, the following
       default completion function would load completions dynamically:

       _completion_loader()
       {
            . "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
       }
       complete -D -F _completion_loader -o bashdefault -o default

HISTORY

       When the -o history option to the set builtin  is  enabled,  the  shell
       provides access to the command history, the list of commands previously
       typed.  The value of the HISTSIZE variable is used  as  the  number  of
       commands  to  save  in  a  history list.  The text of the last HISTSIZE
       commands (default 500) is saved.  The shell stores each command in  the
       history  list  prior to parameter and variable expansion (see EXPANSION
       above) but after history expansion is performed, subject to the  values
       of the shell variables HISTIGNORE and HISTCONTROL.

       On  startup,  the  history  is  initialized  from the file named by the
       variable HISTFILE (default ~/.bash_history).  The  file  named  by  the
       value  of  HISTFILE is truncated, if necessary, to contain no more than
       the number of  lines  specified  by  the  value  of  HISTFILESIZE.   If
       HISTFILESIZE  is  unset,  or  set  to  null,  a non-numeric value, or a
       numeric value less than zero, the history file is not truncated.   When
       the  history  file  is  read,  lines beginning with the history comment
       character followed immediately by a digit are interpreted as timestamps
       for  the  preceding  history  line.   These  timestamps  are optionally
       displayed depending on the value of the HISTTIMEFORMAT variable.   When
       a shell with history enabled exits, the last $HISTSIZE lines are copied
       from the history list to $HISTFILE.  If the histappend shell option  is
       enabled  (see  the  description  of  shopt under SHELL BUILTIN COMMANDS
       below), the lines are appended  to  the  history  file,  otherwise  the
       history  file  is overwritten.  If HISTFILE is unset, or if the history
       file is unwritable, the history is not saved.   If  the  HISTTIMEFORMAT
       variable  is  set,  time stamps are written to the history file, marked
       with the history comment character, so they  may  be  preserved  across
       shell sessions.  This uses the history comment character to distinguish
       timestamps from other history lines.  After  saving  the  history,  the
       history  file  is truncated to contain no more than HISTFILESIZE lines.
       If HISTFILESIZE is unset, or set to null, a  non-numeric  value,  or  a
       numeric value less than zero, the history file is not truncated.

       The  builtin  command fc (see SHELL BUILTIN COMMANDS below) may be used
       to list or edit and re-execute a portion  of  the  history  list.   The
       history  builtin  may be used to display or modify the history list and
       manipulate the history file.  When using command-line  editing,  search
       commands  are available in each editing mode that provide access to the
       history list.

       The shell allows control over which commands are saved on  the  history
       list.  The HISTCONTROL and HISTIGNORE variables may be set to cause the
       shell to save only a subset of the commands entered.  The cmdhist shell
       option,  if enabled, causes the shell to attempt to save each line of a
       multi-line command in the same history entry, adding  semicolons  where
       necessary  to preserve syntactic correctness.  The lithist shell option
       causes the shell to save the command with embedded newlines instead  of
       semicolons.  See the description of the shopt builtin below under SHELL
       BUILTIN  COMMANDS  for  information  on  setting  and  unsetting  shell
       options.

HISTORY EXPANSION

       The  shell  supports a history expansion feature that is similar to the
       history expansion in csh.  This section describes what syntax  features
       are  available.   This  feature  is  enabled by default for interactive
       shells, and can be disabled using the +H  option  to  the  set  builtin
       command  (see SHELL BUILTIN COMMANDS below).  Non-interactive shells do
       not perform history expansion by default.

       History expansions introduce words from the history list into the input
       stream,  making  it  easy to repeat commands, insert the arguments to a
       previous command into the current input line, or fix errors in previous
       commands quickly.

       History  expansion  is  performed  immediately after a complete line is
       read, before the shell breaks it into words.  It  takes  place  in  two
       parts.   The  first is to determine which line from the history list to
       use during substitution.  The second is to select portions of that line
       for inclusion into the current one.  The line selected from the history
       is the event, and the portions of that line that  are  acted  upon  are
       words.   Various  modifiers  are  available  to manipulate the selected
       words.  The line is broken into words  in  the  same  fashion  as  when
       reading input, so that several metacharacter-separated words surrounded
       by quotes are considered one word.  History expansions  are  introduced
       by  the  appearance  of  the history expansion character, which is ! by
       default.  Only backslash (\) and single quotes can  quote  the  history
       expansion character.

       Several  characters  inhibit  history  expansion  if  found immediately
       following the history expansion character,  even  if  it  is  unquoted:
       space,  tab,  newline,  carriage  return,  and =.  If the extglob shell
       option is enabled, ( will also inhibit expansion.

       Several shell options settable with the shopt builtin may  be  used  to
       tailor  the  behavior  of  history  expansion.  If the histverify shell
       option is enabled (see the description of the shopt builtin below), and
       readline  is  being  used,  history  substitutions  are not immediately
       passed to the shell parser.  Instead, the  expanded  line  is  reloaded
       into the readline editing buffer for further modification.  If readline
       is being used, and the histreedit shell option  is  enabled,  a  failed
       history  substitution will be reloaded into the readline editing buffer
       for correction.  The -p option to the history builtin  command  may  be
       used  to  see what a history expansion will do before using it.  The -s
       option to the history builtin may be used to add commands to the end of
       the  history  list  without  actually  executing them, so that they are
       available for subsequent recall.

       The shell allows control of the various characters used by the  history
       expansion mechanism (see the description of histchars above under Shell
       Variables).  The shell uses  the  history  comment  character  to  mark
       history timestamps when writing the history file.

   Event Designators
       An  event  designator  is  a  reference  to a command line entry in the
       history list.  Unless the reference is absolute, events are relative to
       the current position in the history list.

       !      Start  a  history substitution, except when followed by a blank,
              newline, carriage return, = or ( (when the extglob shell  option
              is enabled using the shopt builtin).
       !n     Refer to command line n.
       !-n    Refer to the current command minus n.
       !!     Refer to the previous command.  This is a synonym for `!-1'.
       !string
              Refer  to the most recent command preceding the current position
              in the history list starting with string.
       !?string[?]
              Refer to the most recent command preceding the current  position
              in  the  history  list containing string.  The trailing ? may be
              omitted if string is followed immediately by a newline.
       ^string1^string2^
              Quick substitution.   Repeat  the  previous  command,  replacing
              string1  with  string2.  Equivalent to ``!!:s/string1/string2/''
              (see Modifiers below).
       !#     The entire command line typed so far.

   Word Designators
       Word designators are used to select desired words from the event.  A  :
       separates  the event specification from the word designator.  It may be
       omitted if the word designator begins with a ^, $, *, -, or  %.   Words
       are  numbered from the beginning of the line, with the first word being
       denoted by  0  (zero).   Words  are  inserted  into  the  current  line
       separated by single spaces.

       0 (zero)
              The zeroth word.  For the shell, this is the command word.
       n      The nth word.
       ^      The first argument.  That is, word 1.
       $      The  last  word.   This  is  usually the last argument, but will
              expand to the zeroth word if there is only one word in the line.
       %      The word matched by the most recent `?string?' search.
       x-y    A range of words; `-y' abbreviates `0-y'.
       *      All of the words but the zeroth.  This is a synonym  for  `1-$'.
              It  is  not  an  error to use * if there is just one word in the
              event; the empty string is returned in that case.
       x*     Abbreviates x-$.
       x-     Abbreviates x-$ like x*, but omits the last word.

       If a word designator is supplied without an  event  specification,  the
       previous command is used as the event.

   Modifiers
       After  the optional word designator, there may appear a sequence of one
       or more of the following modifiers, each preceded by a `:'.

       h      Remove a trailing filename component, leaving only the head.
       t      Remove all leading filename components, leaving the tail.
       r      Remove a trailing suffix of the form .xxx, leaving the basename.
       e      Remove all but the trailing suffix.
       p      Print the new command but do not execute it.
       q      Quote the substituted words, escaping further substitutions.
       x      Quote the substituted words as with q, but break into  words  at
              blanks and newlines.
       s/old/new/
              Substitute  new  for  the  first  occurrence of old in the event
              line.  Any delimiter can be used  in  place  of  /.   The  final
              delimiter  is  optional if it is the last character of the event
              line.  The delimiter may be quoted in old and new with a  single
              backslash.   If  &  appears  in  new,  it is replaced by old.  A
              single backslash will quote the &.  If old is null, it is set to
              the   last   old   substituted,   or,  if  no  previous  history
              substitutions took place,  the  last  string  in  a  !?string[?]
              search.
       &      Repeat the previous substitution.
       g      Cause changes to be applied over the entire event line.  This is
              used in conjunction with `:s' (e.g.,  `:gs/old/new/')  or  `:&'.
              If  used with `:s', any delimiter can be used in place of /, and
              the final delimiter is optional if it is the last  character  of
              the event line.  An a may be used as a synonym for g.
       G      Apply  the following `s' modifier once to each word in the event
              line.

SHELL BUILTIN COMMANDS

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

        .  filename [arguments]
       source filename [arguments]
              Read  and  execute  commands  from filename in the current shell
              environment and return the  exit  status  of  the  last  command
              executed  from  filename.  If filename does not contain a slash,
              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.  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 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; 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]  [-DE]  [-A  action]   [-G
       globpat] [-W wordlist] [-F function] [-C command]
              [-X filterpat] [-P prefix] [-S suffix] name [name ...]
       complete -pr [-DE] [name ...]
              Specify  how arguments to each name should be completed.  If the
              -p option is 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  the
              remaining  options  and  actions should apply to the ``default''
              command completion; that is, completion attempted on  a  command
              for  which  no  completion  has previously been defined.  The -E
              option indicates that the remaining options and  actions  should
              apply  to  ``empty''  command  completion;  that  is, completion
              attempted on a blank line.

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

              Other options, if specified, have the following  meanings.   The
              arguments  to the -G, -W, and -X options (and, if necessary, the
              -P and -S  options)  should  be  quoted  to  protect  them  from
              expansion before the complete builtin is invoked.
              -o comp-option
                      The   comp-option   controls   several  aspects  of  the
                      compspec's behavior  beyond  the  simple  generation  of
                      completions.  comp-option may be one of:
                      bashdefault
                              Perform the rest of the default bash completions
                              if the compspec generates no matches.
                      default Use readline's default  filename  completion  if
                              the compspec 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).
                      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.   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] [-DE] [+o option] [name]
              Modify  completion  options  for  each  name  according  to  the
              options, or for the currently-executing completion if  no  names
              are  supplied.   If no options are given, display the completion
              options for each name or the current completion.   The  possible
              values  of  option  are  those  valid  for  the complete builtin
              described above.  The -D option  indicates  that  the  remaining
              options should apply to the ``default'' command completion; that
              is, completion attempted on a command for  which  no  completion
              has  previously  been defined.  The -E option indicates that the
              remaining options should apply to ``empty'' command  completion;
              that is, completion attempted on a blank line.

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

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

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

              Using  `+'  instead of `-' turns off the attribute instead, with
              the exceptions that +a may not  be  used  to  destroy  an  array
              variable  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.
              -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 ...]
              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     an escape character
                   form feed
              
     new line
              
     carriage return
              	     horizontal tab
                   vertical tab
              \     backslash
              nnn  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.  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 intepreted  the  same  as
              first  above.  A useful alias to use with this is ``r="fc -s"'',
              so that typing ``r cc'' runs the  last  command  beginning  with
              ``cc'' and typing ``r'' re-executes the last command.

              If  the  first  form  is  used,  the return value is 0 unless an
              invalid option is encountered or first or last  specify  history
              lines  out  of  range.  If the -e option is supplied, the return
              value is the value of the last command executed or failure if an
              error occurs with the temporary file of commands.  If the second
              form is used, the return status  is  that  of  the  command  re-
              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 -anrw [filename]
       history -p arg [arg ...]
       history -s arg [arg ...]
              With no options, display the  command  history  list  with  line
              numbers.  Lines listed with a * have been modified.  An argument
              of n lists only  the  last  n  lines.   If  the  shell  variable
              HISTTIMEFORMAT  is  set  and  not  null,  it is used as a format
              string for strftime(3) to display the time stamp associated with
              each  displayed  history entry.  No intervening blank is printed
              between the formatted time  stamp  and  the  history  line.   If
              filename  is  supplied,  it  is  used as the name of the history
              file; if not, the  value  of  HISTFILE  is  used.   Options,  if
              supplied, have the following meanings:
              -c     Clear the history list by deleting all the entries.
              -d offset
                     Delete the history entry at position offset.
              -a     Append  the  ``new'' history lines (history lines entered
                     since the beginning of the current bash session)  to  the
                     history file.
              -n     Read  the history lines not already read from the history
                     file into the 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 previous  history  line.   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 [sigspec | exit_status]
              Send  the  signal  named  by  sigspec or signum to the processes
              named by pid or jobspec.  sigspec is either  a  case-insensitive
              signal  name such as SIGKILL (with or without the SIG prefix) or
              a signal number; signum is a signal number.  If sigspec  is  not
              present,  then  SIGTERM is assumed.  An argument of -l lists the
              signal names.  If any arguments are supplied when -l  is  given,
              the  names  of  the  signals  corresponding to the arguments are
              listed, and the return status is 0.  The exit_status argument to
              -l  is  a  number  specifying either a signal number or the exit
              status of a process terminated by a signal.  kill  returns  true
              if  at  least  one  signal was successfully sent, or false if an
              error occurs or an invalid option is encountered.

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

       local [option] [name[=value] ...]
              For each argument, a local variable named name is  created,  and
              assigned  value.   The option can be any of the options accepted
              by declare.  When local is used within a function, it causes the
              variable  name  to  have  a  visible  scope  restricted  to that
              function and its children.  With no  operands,  local  writes  a
              list  of local 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 [-n count] [-O origin] [-s count] [-t] [-u  fd]  [-C  callback]
       [-c quantum] [array]
       readarray  [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback]
       [-c quantum] [array]
              Read lines from  the  standard  input  into  the  indexed  array
              variable  array,  or from file descriptor fd if the -u option is
              supplied.  The variable MAPFILE is the default array.   Options,
              if supplied, have the following meanings:
              -n     Copy  at  most count lines.  If count is 0, all lines are
                     copied.
              -O     Begin assigning to array at index  origin.   The  default
                     index is 0.
              -s     Discard the first count lines read.
              -t     Remove a trailing newline from each line read.
              -u     Read  lines  from  file  descriptor  fd  instead  of  the
                     standard input.
              -C     Evaluate callback each time quantum lines are read.   The
                     -c option specifies quantum.
              -c     Specify  the  number  of  lines read between each call to
                     callback.

              If -C is specified without -c,  the  default  quantum  is  5000.
              When callback is 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 (except that \c terminates output,
                     backslashes in \', \", and \? are not removed, and  octal
                     escapes beginning with  may contain up to four digits).
              %q     causes  printf  to output the corresponding argument in a
                     format that can be reused as shell input.
              %(datefmt)T
                     causes printf to output the  date-time  string  resulting
                     from  using  datefmt  as a format string for strftime(3).
                     The corresponding argument is an integer representing the
                     number  of seconds since the epoch.  Two special argument
                     values may be used: -1 represents the current  time,  and
                     -2  represents  the  time  the  shell was invoked.  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, exchanges the top two directories
              and returns 0, unless the directory stack is empty.   Arguments,
              if supplied, have the following meanings:
              -n     Suppresses  the  normal  change  of directory when adding
                     directories to the stack,  so  that  only  the  stack  is
                     manipulated.
              +n     Rotates  the  stack  so  that the nth directory (counting
                     from the left of the list shown by  dirs,  starting  with
                     zero) is at the top.
              -n     Rotates  the  stack  so  that the nth directory (counting
                     from the right of the list shown by dirs,  starting  with
                     zero) is at the top.
              dir    Adds dir to the directory stack at the top, making it the
                     new current 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, and  the
              first word is assigned to the first name, the second word to the
              second  name,  and  so  on,  with  leftover  words   and   their
              intervening  separators assigned to the last name.  If there are
              fewer words read from the input stream than names, the remaining
              names are assigned empty values.  The characters in IFS are used
              to split the line into words 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.
              -e     If the standard input is coming from a terminal, readline
                     (see   READLINE  above)  is  used  to  obtain  the  line.
                     Readline uses the current (or default,  if  line  editing
                     was not previously active) editing settings.
              -i text
                     If  readline  is  being  used  to  read the line, text is
                     placed into the editing buffer before editing begins.
              -n nchars
                     read returns after reading nchars characters rather  than
                     waiting  for  a  complete  line  of  input,  but  honor a
                     delimiter if fewer than nchars characters are read before
                     the delimiter.
              -N nchars
                     read  returns  after  reading  exactly  nchars characters
                     rather than waiting for a complete line of input,  unless
                     EOF   is   encountered  or  read  times  out.   Delimiter
                     characters encountered  in  the  input  are  not  treated
                     specially  and  do  not cause read to return until nchars
                     characters are read.
              -p prompt
                     Display prompt on  standard  error,  without  a  trailing
                     newline, before attempting to read any input.  The prompt
                     is displayed only if input is 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 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 return code is zero, unless end-of-file is
              encountered, read times out (in which case the  return  code  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  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      Automatically mark variables  and  functions  which  are
                      modified  or  created  for  export to the environment of
                      subsequent commands.
              -b      Report  the  status  of   terminated   background   jobs
                      immediately, rather than before the next primary prompt.
                      This is effective only when job control is enabled.
              -e      Exit immediately if a pipeline (which may consist  of  a
                      single  simple  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.  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:

              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 command
                      and, if necessary,  updates  the  values  of  LINES  and
                      COLUMNS.
              cmdhist If  set,  bash attempts to save all lines of a multiple-
                      line command in the same  history  entry.   This  allows
                      easy re-editing of multi-line commands.
              compat31
                      If set, bash changes its behavior to that of version 3.1
                      with respect to quoted arguments to the  [[  conditional
                      command's   =~   operator   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).
              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.
              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.
              execfail
                      If set, a non-interactive shell  will  not  exit  if  it
                      cannot  execute the file specified as an argument to the
                      exec builtin command.  An  interactive  shell  does  not
                      exit if exec fails.
              expand_aliases
                      If  set,  aliases  are expanded as described above under
                      ALIASES.   This  option  is  enabled  by   default   for
                      interactive shells.
              extdebug
                      If  set,  behavior  intended  for  use  by  debuggers is
                      enabled:
                      1.     The -F option to the declare builtin displays the
                             source file name and line number corresponding to
                             each function name supplied as an argument.
                      2.     If the command run by the DEBUG  trap  returns  a
                             non-zero  value,  the next command is skipped and
                             not executed.
                      3.     If the command run by the DEBUG  trap  returns  a
                             value  of  2,  and  the  shell  is executing in a
                             subroutine (a shell function or  a  shell  script
                             executed  by the . or source builtins), a call to
                             return is simulated.
                      4.     BASH_ARGC and BASH_ARGV are updated as  described
                             in their 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.
              interactive_comments
                      If set, allow a word beginning with # to cause that word
                      and all remaining characters on that line to be  ignored
                      in  an  interactive  shell  (see  COMMENTS above).  This
                      option is enabled by default.
              lastpipe
                      If set, and job control is not active,  the  shell  runs
                      the  last  command  of  a  pipeline  not executed in the
                      background in the current shell environment.
              lithist If set, and the cmdhist option  is  enabled,  multi-line
                      commands are saved to the history with embedded newlines
                      rather than using semicolon separators where possible.
              login_shell
                      The shell sets this option if it is started as  a  login
                      shell  (see  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.
              nullglob
                      If  set,  bash allows patterns which match no files (see
                      Pathname Expansion above) to expand to  a  null  string,
                      rather than themselves.
              progcomp
                      If  set,  the  programmable  completion  facilities (see
                      Programmable Completion above) are enabled.  This option
                      is enabled by default.
              promptvars
                      If  set,  prompt  strings  undergo  parameter expansion,
                      command substitution, arithmetic  expansion,  and  quote
                      removal  after  being expanded as described in PROMPTING
                      above.  This option is enabled by default.
              restricted_shell
                      The  shell  sets  this  option  if  it  is  started   in
                      restricted mode (see RESTRICTED SHELL below).  The value
                      may not be changed.  This is not reset when the  startup
                      files  are  executed,  allowing  the  startup  files  to
                      discover whether or not a shell is restricted.
              shift_verbose
                      If set, the shift builtin prints an error  message  when
                      the   shift  count  exceeds  the  number  of  positional
                      parameters.
              sourcepath
                      If set, the source (.) builtin uses the value of PATH to
                      find  the  directory  containing the file supplied as an
                      argument.  This option is enabled by default.
              xpg_echo
                      If  set,  the  echo  builtin  expands   backslash-escape
                      sequences by default.

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

       test expr
       [ expr ]
              Return  a  status  of  0  (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 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 [-HSTabcdefilmnpqrstuvx [limit]]
              Provides control over the resources available to the  shell  and
              to  processes started by it, on systems that allow such control.
              The -H and -S options specify that the hard or soft limit is set
              for  the  given resource.  A hard limit cannot be increased by a
              non-root user once it is set; a soft limit may be  increased  up
              to  the  value  of  the  hard  limit.   If  neither -H nor -S is
              specified, both the soft and hard limits are set.  The value  of
              limit  can be a number in the unit specified for the resource or
              one of the special values hard, soft, or unlimited, which  stand
              for  the  current  hard  limit,  the  current soft limit, and no
              limit, respectively.  If limit is 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
              -l     The maximum size that may be locked into memory
              -m     The  maximum resident set size (many systems do not honor
                     this limit)
              -n     The maximum number of open file descriptors (most systems
                     do not allow this value to be set)
              -p     The pipe size in 512-byte blocks (this may not be set)
              -q     The maximum number of bytes in POSIX message queues
              -r     The maximum real-time scheduling priority
              -s     The maximum stack size
              -t     The maximum amount of cpu time in seconds
              -u     The  maximum  number  of  processes available to a single
                     user
              -v     The maximum amount of virtual  memory  available  to  the
                     shell and, on some systems, to its children
              -x     The maximum number of file locks
              -T     The maximum number of threads

              If  limit  is given, 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;  and -T, -b, -n, and -u, which are unscaled values.  The
              return status is 0 unless  an  invalid  option  or  argument  is
              supplied, or an error occurs while setting a new limit.

       umask [-p] [-S] [mode]
              The user file-creation mask is set to mode.  If mode begins with
              a digit, it is interpreted as an octal number; otherwise  it  is
              interpreted  as a symbolic mode mask similar to that accepted by
              chmod(1).  If mode is omitted, the current value of the mask  is
              printed.   The  -S  option  causes  the  mask  to  be printed in
              symbolic form; the default output is an octal number.  If the -p
              option is supplied, and mode is 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 [-n] [n ...]
              Wait for each specified child process and return its termination
              status.  Each n may be a process ID or a job specification; if a
              job  spec  is  given,  all  processes in that job's pipeline are
              waited for.  If n is  not  given,  all  currently  active  child
              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 n specifies a non-existent process
              or job, the return status is 127.  Otherwise, the return  status
              is the exit status of the last process or job waited for.

RESTRICTED SHELL

       If bash is started with the name rbash, or the -r option is supplied at
       invocation, the shell becomes restricted.  A restricted shell  is  used
       to  set  up an environment more controlled than the standard shell.  It
       behaves identically to bash with the exception that the  following  are
       disallowed or not performed:

       ·      changing directories with cd

       ·      setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV

       ·      specifying command names containing /

       ·      specifying  a  filename  containing  a / as an argument to the .
              builtin command

       ·      specifying a filename containing a slash as an argument  to  the
              -p option to the hash builtin command

       ·      importing  function  definitions  from  the shell environment at
              startup

       ·      parsing the value of SHELLOPTS from  the  shell  environment  at
              startup

       ·      redirecting  output  using  the  >,  >|,  <>,  >&,  &>,  and  >>
              redirection operators

       ·      using the exec builtin command to replace the shell with another
              command

       ·      adding  or  deleting builtin commands with the -f and -d options
              to the enable builtin command

       ·      using the  enable  builtin  command  to  enable  disabled  shell
              builtins

       ·      specifying the -p option to the command builtin command

       ·      turning off restricted mode with set +r or set +o restricted.

       These restrictions are enforced after any startup files are read.

       When  a  command  that  is  found to be a shell script is executed (see
       COMMAND EXECUTION above), rbash turns off any restrictions in the shell
       spawned to execute the script.

SEE ALSO

       Bash Reference Manual, Brian Fox and Chet Ramey
       The Gnu Readline Library, Brian Fox and Chet Ramey
       The Gnu History Library, Brian Fox and Chet Ramey
       Portable   Operating   System  Interface  (POSIX)  Part  2:  Shell  and
       Utilities, IEEE --
              http://pubs.opengroup.org/onlinepubs/9699919799/
       http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
       sh(1), ksh(1), csh(1)
       emacs(1), vi(1)
       readline(3)

FILES

       /bin/bash
              The bash executable
       /etc/profile
              The systemwide initialization file, executed for login shells
       /etc/bash.bashrc
              The systemwide per-interactive-shell startup file
       /etc/bash.bash.logout
              The systemwide login shell cleanup file, executed when  a  login
              shell exits
       ~/.bash_profile
              The personal initialization file, executed for login shells
       ~/.bashrc
              The individual per-interactive-shell startup file
       ~/.bash_logout
              The  individual  login shell cleanup file, executed when a login
              shell exits
       ~/.inputrc
              Individual readline initialization file

AUTHORS

       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet.ramey@case.edu

BUG REPORTS

       If you find a bug in bash, you should report it.  But first, you should
       make  sure  that  it really is a bug, and that it appears in the latest
       version  of  bash.   The  latest  version  is  always  available   from
       ftp://ftp.gnu.org/pub/gnu/bash/.

       Once  you  have  determined that a bug actually exists, use the bashbug
       command to submit a bug report.  If you have a fix, you are  encouraged
       to  mail that as well!  Suggestions and `philosophical' bug reports may
       be mailed  to  bug-bash@gnu.org  or  posted  to  the  Usenet  newsgroup
       gnu.bash.bug.

       ALL bug reports should include:

       The version number of bash
       The hardware and operating system
       The compiler used to compile
       A description of the bug behaviour
       A short script or `recipe' which exercises the bug

       bashbug  inserts  the first three items automatically into the template
       it provides for filing a bug report.

       Comments and bug reports concerning this manual page should be directed
       to chet.ramey@case.edu.

BUGS

       It's too big and too slow.

       There are some subtle differences between bash and traditional versions
       of sh, mostly because of the POSIX specification.

       Aliases are confusing in some uses.

       Shell builtin commands and functions are not stoppable/restartable.

       Compound commands and command sequences of the form `a ; b ; c' are not
       handled  gracefully  when  process  suspension  is  attempted.   When a
       process is stopped, the shell immediately executes the next command  in
       the  sequence.   It  suffices to place the sequence of commands between
       parentheses to force it into a subshell, which  may  be  stopped  as  a
       unit.

       Array variables may not (yet) be exported.

       There may be only one active coprocess at a time.



  All copyrights belong to their respective owners. Other content (c) 2014-2017, GNU.WIKI. Please report site errors to webmaster@gnu.wiki.
Page load time: 0.091 seconds. Last modified: September 11 2017 23:31:28.