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BASH(1)			    General Commands Manual		       BASH(1)



NAME
       bash - GNU Bourne-Again SHell

SYNOPSIS
       bash [options] [file]

COPYRIGHT
       Bash is Copyright (C) 1989-2011 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 incor-
       porates 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 descrip-
       tion 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 string If the -c option is present,  then  commands  are  read  from
		 string.   If  there  are arguments after the 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  sub-
		 ject 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	 file-
		 names 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 (por-
	      table object) file format.
       --dump-strings
	      Equivalent to -D.
       --help Display a usage message on standard  output  and	exit  success-
	      fully.
       --init-file file
       --rcfile file
	      Execute commands from file instead of the standard personal ini-
	      tialization 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	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).

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

       --rpm-requires
	      Produce the list of files that are required for the shell script
	      to run.  This implies '-n' and is subject to  the	 same  limita-
	      tions as compile time error checking checking; Command substitu-
	      tions, Conditional expressions and eval builtin are  not	parsed
	      so some dependencies may be missed.

       --verbose
	      Equivalent to  -v.

       --version
	      Show  version information for this instance of bash on the stan-
	      dard 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 parame-
       ters are set to the remaining arguments.	 Bash reads and executes  com-
       mands  from this file, then exits.  Bash's exit status is the exit sta-
       tus 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 file names as described below under Tilde Expan-
       sion in the EXPANSION section.

       When  bash is invoked as an interactive login shell, or as a non-inter-
       active shell with the --login option, it first reads and executes  com-
       mands  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
       files ~/.bash_logout and /etc/bash.bash_logout, if the files exists.

       When an interactive shell that is not a login shell  is	started,  bash
       reads  and executes commands from ~/.bashrc, if that file exists.  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
       ~/.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 com-
       mand were executed:
	      if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
       but the value of the PATH variable is not used to search for  the  file
       name.

       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 interac-
       tive 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 exe-
       cute  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	deter-
       mines  it  is being run in this fashion, it reads and executes commands
       from ~/.bashrc, if that file exists and is 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  rshd  does  not	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 docu-
       ment.
       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 under-
	      scores, and beginning with an alphabetic character or an	under-
	      score.  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 fol-
	      lowing 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  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 fol-
       lowed 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  redirec-
       tions specified by the command (see REDIRECTION below).	If |& is used,
       the standard error of command is connected to command2's standard input
       through	the pipe; it is shorthand for 2>&1 |.  This implicit redirect-
       ion of the standard error 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  success-
       fully.  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 rec-
       ognize 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 exe-
       cutes 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:

       (list) list  is	executed in a subshell environment (see COMMAND EXECU-
	      TION ENVIRONMENT below).	Variable assignments and builtin  com-
	      mands  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 expres-
	      sion 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.	Condi-
	      tional operators such as -f must be unquoted to be recognized as
	      primaries.

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

	      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.	 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 pat-
	      tern, and 1 otherwise.  Any part of the pattern may be quoted to
	      force it 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 expres-
	      sion 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 it 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 parenthe-
	      sized 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	 omit-
	      ted,  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 expres-
	      sions 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 stan-
	      dard 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  dis-
	      played 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 path-
	      name expansion (see Pathname  Expansion  below).	 The  word  is
	      expanded	using  tilde  expansion, parameter and variable expan-
	      sion, arithmetic	substitution,  command	substitution,  process
	      substitution  and	 quote	removal.   Each	 pattern  examined  is
	      expanded using tilde expansion, parameter	 and  variable	expan-
	      sion, 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  sta-
	      tus 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 exe-
	      cuted.

   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 sim-
       ple command (see above); otherwise, it is interpreted as the first word
       of  the simple command.	When the coproc 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  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.

       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 com-
	      pound 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.	  com-
	      pound-command is executed whenever name is specified as the name
	      of a simple command.  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 inter-
       active_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 interac-
       tive 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  HIS-
       TORY 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
	      \E     an escape character
	      \f     form feed
	      \n     new line
	      \r     carriage return
	      \t     horizontal tab
	      \v     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 num-
       ber, or one of the special characters listed below under Special Param-
       eters.	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,  com-
       mand  substitution, arithmetic expansion, and quote removal (see EXPAN-
       SION 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	state-
       ments  may  also	 appear	 as  arguments to the alias, declare, typeset,
       export, readonly, and local builtin commands.

       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 vari-
       able  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.

   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 occurs within double quotes, it expands to a sin-
	      gle word with the value of each parameter separated by the first
	      character of the IFS special variable.  That is, "$*" is equiva-
	      lent to "$1c$2c...", where c is the first character of the value
	      of  the IFS variable.  If IFS is unset, the parameters are sepa-
	      rated by spaces.	If IFS is  null,  the  parameters  are	joined
	      without intervening separators.
       @      Expands  to  the positional parameters, starting from one.  When
	      the  expansion  occurs  within  double  quotes,  each  parameter
	      expands to a separate word.  That is, "$@" is equivalent to "$1"
	      "$2" ...	If the double-quoted expansion occurs within  a	 word,
	      the  expansion  of the first parameter is joined with the begin-
	      ning part of the original word, and the expansion	 of  the  last
	      parameter	 is  joined  with  the last part of the original word.
	      When there are no positional parameters, "$@" 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 fore-
	      ground pipeline.
       -      Expands to the current option flags as  specified	 upon  invoca-
	      tion,  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 sub-
	      shell.
       !      Expands to the process ID of the most  recently  executed	 back-
	      ground (asynchronous) command.
       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 com-
	      mands,  $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 file name 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	 envi-
	      ronment  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 check-
	      ing  mail,  this	parameter holds the name of the mail file cur-
	      rently being checked.

   Shell Variables
       The following variables are set by the shell:

       BASH   Expands to the full file name 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 cur-
	      rent 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 exe-
	      cuted,  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 func-
	      tion).  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 vari-
	      able 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 each time a subshell or subshell environment
	      is spawned.  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 func-
	      tions  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 cur-
	      rent completion function.
       COMP_LINE
	      The  current  command  line.  This variable is available only in
	      shell functions and external commands invoked  by	 the  program-
	      mable completion facilities (see Programmable Completion below).
       COMP_POINT
	      The  index of the current cursor position relative to the begin-
	      ning 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 program-
	      mable 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  succes-
	      sive  tabs,  !, for listing alternatives on partial word comple-
	      tion, @, 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  program-
	      mable 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 subse-
	      quently reset.
       COMP_WORDS
	      An array variable (see Arrays below) consisting of the  individ-
	      ual  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 func-
	      tions 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 con-
	      tents 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 directo-
	      ries  already in the stack, but the pushd and popd builtins must
	      be used to add and remove directories.  Assignment to this vari-
	      able  will  not  change  the  current directory.	If DIRSTACK is
	      unset, it loses its special properties, even  if	it  is	subse-
	      quently reset.
       EUID   Expands  to  the effective user ID of the current user, initial-
	      ized 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 bot-
	      tom-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 sta-
	      tus.  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 infor-
	      mation.
       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 proper-
	      ties, 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-com-
	      pany-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  sys-
	      tem  on  which  bash is executing.  The default is system-depen-
	      dent.
       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	 read-
	      only.
       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_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 file name.
	      PATH is not used to search for the resultant file name.
       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".
       COLUMNS
	      Used by the select compound command to  determine	 the  terminal
	      width  when  printing  selection	lists.	Automatically set 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 com-
	      pletion facility (see Programmable Completion below).
       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 suf-
	      fix  matches  one of the entries in FIGNORE is excluded from the
	      list of matched filenames.  A sample value is ".o:~".
       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 HIS-
	      TORY  below).   The default value is ~/.bash_history.  If unset,
	      the command history is  not  saved  when	an  interactive	 shell
	      exits.
       HISTFILESIZE
	      The maximum number of lines contained in the history file.  When
	      this variable is assigned a value, the  history  file  is	 trun-
	      cated,  if necessary, by removing the oldest entries, to contain
	      no more than that number of lines.  The default  value  is  500.
	      The history file is also truncated to this size after writing it
	      when an interactive shell exits.
       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  com-
	      plete  line  (no	implicit  `*'  is  appended).  Each pattern is
	      tested against the line after the checks specified  by  HISTCON-
	      TROL  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).  The default value is 500.
       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  comple-
	      tions.  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><new-
	      line>''.
       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 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	direc-
	      tory.
       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  file names to be checked for mail.
	      The message to be printed when mail arrives in a particular file
	      may  be  specified  by separating the file name 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	 loca-
	      tion  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/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.
       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-\v\$ ''.
       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  mul-
	      tiple  times, as necessary, to indicate multiple levels of indi-
	      rection.	The default is ``+ ''.
       SHELL  The full pathname to the shell is kept in this environment vari-
	      able.   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  specify-
	      ing  how	the timing information for pipelines prefixed with the
	      time reserved word should be displayed.  The % character	intro-
	      duces  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
	      $'\nreal\t%3lR\nuser\t%3lU\nsys%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 termi-
	      nates 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 input after
	      issuing the primary prompt.  Bash terminates after  waiting  for
	      that number of seconds if 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 com-
	      mands without redirections are treated as candidates for resump-
	      tion 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	analo-
	      gous  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, substi-
	      tuting one string for another in the command.   The  default  is
	      `^'.   The optional third character is the character which indi-
	      cates that the remainder of the line is a comment when found  as
	      the  first  character of a word, normally `#'.  The history com-
	      ment 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 con-
       tiguously.  Indexed arrays are  referenced  using  integers  (including
       arithmetic  expressions)	  and  are  zero-based; associative arrays are
       referenced using arbitrary strings.

       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.	 If  subscript
       evaluates  to a number less than zero, it is used as an offset from one
       greater than the array's maximum index (so a subcript of -1  refers  to
       the  last  element  of  the  array).   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 [sub-
       script]=string.	Indexed array assignments do not require  the  bracket
       and  subscript.	 When  assigning  to  indexed  arrays, if the optional
       brackets and subscript are supplied, that index is assigned to;	other-
       wise 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.

       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 sep-
       arate  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[sub-
       script]}.  If subscript is * or @, the expansion is the number of  ele-
       ments  in the array.  Referencing an array variable without a subscript
       is equivalent to referencing the array with a subscript of 0.

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

       The  unset  builtin  is	used to destroy arrays.	 unset name[subscript]
       destroys the array element at index subscript.  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  substitu-
       tion, arithmetic expansion, word splitting, and pathname expansion.

       The  order  of expansions is: brace expansion, tilde expansion, parame-
       ter, variable and 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 avail-
       able: process 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 gener-
       ated.  This mechanism is similar to pathname expansion, but  the	 file-
       names generated need not exist.	Patterns to be brace expanded take the
       form of an optional preamble, followed by either a series of comma-sep-
       arated  strings or a sequence expression between a pair of braces, fol-
       lowed 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 pre-
       fixed 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	neces-
       sary.   When  characters	 are  supplied, the expression expands to each
       character lexicographically between x and y, inclusive.	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 char-
       acters 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	expan-
       sion, 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 com-
       mand (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	direc-
       tory  of	 the  user executing the shell is substituted instead.	Other-
       wise, 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 char-
       acters 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 argu-
       ment.  If the characters following the tilde in the  tilde-prefix  con-
       sist 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 immedi-
       ately following a : or the first =.  In these cases, tilde expansion is
       also performed.	Consequently, one may use file names  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.

       If the first character of parameter is  an  exclamation	point  (!),  a
       level  of  variable  indirection is introduced.	Bash uses the value of
       the variable formed from the rest of parameter as the name of the vari-
       able; 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 expan-
       sions 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, parame-
       ter expansion, command substitution, and arithmetic expansion.

       When  not  performing  substring	 expansion, using the forms documented
       below, 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 expan-
	      sion 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 param-
	      eter  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
	      parameter starting at the character  specified  by  offset.   If
	      length  is omitted, expands to the substring of parameter start-
	      ing at the character specified by offset.	 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 from the end of the value of parameter.  If length
	      evaluates to a number less than zero, and parameter is not @ and
	      not  an  indexed	or  associative array, it is interpreted as an
	      offset from the end of the value of parameter rather than a num-
	      ber  of  characters, and the expansion is the characters between
	      the two offsets.	If parameter is @, the result is length	 posi-
	      tional  parameters  beginning  at	 offset.   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 max-
	      imum  index of the specified array.  Substring expansion applied
	      to an associative array produces undefined results.  Note that a
	      negative offset must be separated from the colon by at least one
	      space to avoid being confused with the :- expansion.   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 pre-
	      fixed 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  parame-
	      ter  is  an  array name subscripted by * or @, the value substi-
	      tuted is the number of elements in the array.

       ${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  pat-
	      tern  (the  ``##''  case)	 deleted.  If parameter is @ or *, the
	      pattern removal operation is applied to each positional  parame-
	      ter in turn, and the expansion is the resultant list.  If param-
	      eter 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	 posi-
	      tional  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 pat-
	      tern  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 begin-
	      ning 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 / fol-
	      lowing pattern may be omitted.  If parameter is @ or *, the sub-
	      stitution 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	alpha-
	      betic  characters in parameter.  The pattern is expanded to pro-
	      duce a pattern just as in pathname expansion.   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 omit-
	      ted, 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 com-
       mand name.  There are two forms:

	      $(command)
       or
	      `command`

       Bash performs the expansion by executing command and replacing the com-
       mand 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 sub-
       stitution.  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	expan-
       sion is:

	      $((expression))

       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 expansion, string expansion,
       command substitution, and quote removal.	 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 out-
       put 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  pro-
       vide  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  substitu-
       tion,  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 on these characters.	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 file names matching the pattern.	 If no
       matching file names 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 alpha-
       betic characters.  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,	 fail-
       glob, and dotglob shell options.

       The  GLOBIGNORE	shell variable may be used to restrict the set of file
       names matching a pattern.  If GLOBIGNORE is  set,  each	matching  file
       name  that  also	 matches  one of the patterns in GLOBIGNORE is removed
       from the list of matches.  The file names ``.''	and ``..''  are always
       ignored	when GLOBIGNORE is set and not null.  However, setting GLOBIG-
       NORE to a non-null value has the effect of enabling the	dotglob	 shell
       option, so all other file names beginning with a ``.''  will match.  To
       get the old behavior of ignoring file names  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 subdirecto-
		     ries.
	      ?	     Matches any single character.
	      [...]  Matches any one of the enclosed characters.   A  pair  of
		     characters	 separated by a hyphen denotes a range expres-
		     sion; any character that sorts between those two  charac-
		     ters,  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 charac-
		     ter not enclosed is matched.  The sorting order of	 char-
		     acters  in range expressions is determined by the current
		     locale and the value of the LC_COLLATE shell variable, if
		     set.   A - may be matched by including it as the first or
		     last character in the set.	 A ] may be matched by includ-
		     ing 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 collat-
		     ing symbol symbol.

       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

       If the extglob shell option is enabled using the shopt builtin, follow-
       ing pattern matching operator is recognized as well:

	      !(pattern-list)
		     Matches anything except one of the given patterns

   Quote Removal
       After the preceding expansions, all unquoted occurrences of the charac-
       ters  \,	 ', 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 may
       also be used to open and close files for 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 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	 omit-
       ted,  and the first character of the redirection operator is <, the re-
       direction 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  descrip-
       tions,  unless  otherwise noted, is subjected to brace expansion, tilde
       expansion, parameter expansion, command substitution, arithmetic expan-
       sion,  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 out-
       put was redirected to dirlist.

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

	      /dev/fd/fd
		     If	 fd  is	 a valid integer, file descriptor fd is dupli-
		     cated.
	      /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 a TCP connection to the corresponding 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 a UDP connection to the corresponding 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 inter-
       nally.

   Redirecting Input
       Redirection of input causes the file whose name results from the expan-
       sion  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 re-
       direction 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 equiva-
       lent to

	      >word 2>&1

   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

   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 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, com-
       mand substitution, and arithmetic expansion.  In the latter  case,  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 is expanded and supplied 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	evalu-
       ates  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  re-
       direction  error	 occurs.  As a special case, if n is omitted, and word
       does not expand to one or more digits, 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  com-
       pound 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 com-
       pound 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 func-
       tion 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 func-
       tion 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 type-
       set  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 iden-
       tically-named  entries  in  the environment passed to the shell's chil-
       dren.  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 func-
       tion 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  per-
       formed 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.	 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  pri-
       maries 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 sym-
       bolic 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  num-
	      bers.
       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).
       -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.

       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 vari-
	      able.

       If no command name results, the variable assignments affect the current
       shell  environment.  Otherwise, the variables are added to the environ-
       ment of the executed command and do not affect the current shell	 envi-
       ronment.	  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	expan-
       sions  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 con-
       taining 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 execu-
       tion environment.  Argument 0 is set to the name given, and the remain-
       ing 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 exe-
       cutable 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  follow-
       ing:

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

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

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

       o      current traps set by trap

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

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

       o      options enabled at invocation (either by default	or  with  com-
	      mand-line arguments) or by set

       o      options enabled by shopt

       o      shell aliases defined with alias

       o      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 con-
       sists of the following.	Unless otherwise noted, the values are	inher-
       ited from the shell.


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

       o      the current working directory

       o      the file creation mode mask

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

       o      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 asynchro-
       nous 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 invoca-
       tion.  Builtin commands that are invoked as part of a pipeline are also
       executed in a subshell environment.  Changes made to the subshell envi-
       ronment 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  pro-
       cesses.	 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 envi-
       ronment 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	 modi-
       fied  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 envi-
       ronment 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 file name of the command and passed to that command in  its	 envi-
       ronment.

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 substi-
       tution ignore the keyboard-generated job control signals SIGTTIN, SIGT-
       TOU, 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 com-
       mand 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 sta-
       tus 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-gen-
       erated 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 (typ-
       ically ^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 charac-
       ter % 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 cur-
       rent 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 pre-
       vious  job  with	 a -.  A single % (with no accompanying job specifica-
       tion) 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, run-
       ning), 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
	      \e     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
	      \n     newline
	      \r     carriage return
	      \s     the name of the shell, the basename of  $0	 (the  portion
		     following the final slash)
	      \t     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
	      \v     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	 vari-
		     able)
	      \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 substitu-
       tion, 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  interac-
       tive 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.	 Simi-
       larly, meta keys are denoted by M-key, so M-x means Meta-X.   (On  key-
       boards  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  con-
       structs.	 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  univer-
       sal-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 speci-
       fied 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
	      "\e[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
	      \e     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
	      \f     form feed
	      \n     newline
	      \r     carriage return
	      \t     horizontal tab
	      \v     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 func-
       tion 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	 modi-
       fied  with  the bind builtin command.  The editing mode may be switched
       during interactive use by using the -o option to the set	 builtin  com-
       mand (see SHELL BUILTIN COMMANDS below).

   Readline Variables
       Readline has variables that can be used to further customize its behav-
       ior.  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-insen-
       sitive), 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 read-
	      line equivalents.
       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 pos-
	      sible 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	possi-
	      ble completions.
       completion-query-items (100)
	      This  determines when the user is queried about viewing the num-
	      ber of possible completions generated  by	 the  possible-comple-
	      tions  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 sim-
	      ilar 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 gener-
	      ated from the keyboard.
       enable-keypad (Off)
	      When set to On, readline will try to enable the application key-
	      pad  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-his-
	      tory or next-history.
       history-size (0)
	      Set  the	maximum number of history entries saved in the history
	      list.  If set to zero, the number of entries in the history list
	      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  com-
	      mand.   If this variable has not been given a value, the charac-
	      ters 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-com-
	      mand, 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.
       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  dis-
	      played with a preceding asterisk (*).
       mark-symlinked-directories (Off)
	      If set to On, completed names which are symbolic links to direc-
	      tories  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 dis-
	      play 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, his-
	      tory 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	possi-
	      ble  partial  completion (the possible completions don't share a
	      common prefix)  cause  the  matches  to  be  listed  immediately
	      instead of ringing the bell.
       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 com-
	      pletions.

   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 edit-
	      ing 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 ter-
		     minal  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": "\eb\"\ef\""
		     $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 follow-
	      ing 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, read-
       line 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	termi-
       nate 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 accom-
       panying key sequence are unbound by default.  In the following descrip-
       tions,  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 argument, 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 his-
	      tory 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
       delete-char (C-d)
	      Delete the character at point.  If point is at the beginning  of
	      the  line,  there	 are  no  characters in the line, and the last
	      character typed was not bound to delete-char, then return EOF.
       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 cur-
	      sor 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	 argu-
	      ment, 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, charac-
	      ters  bound to self-insert replace the text at point rather than
	      pushing the text	to  the	 right.	  Characters  bound  to	 back-
	      ward-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	bound-
	      ary.  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 bound-
	      aries 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 follow-
	      ing 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 fol-
	      lowed 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 argu-
	      ment 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 com-
	      pletions	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	 char-
	      acters in the macro appear as if typed at the keyboard.

   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	occur-
	      rences.
       character-search-backward (M-C-])
	      A	 character  is	read and point is moved to the previous occur-
	      rence of that character.	A negative count searches  for	subse-
	      quent 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 com-
	      ment-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, other-
	      wise the characters in comment-begin are deleted from the begin-
	      ning  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 file names 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 file names 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	 read-
	      line output stream.  If a numeric argument is supplied, the out-
	      put 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 program-
       mable 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  comple-
       tion 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 consid-
       ered.  The string is first split using the characters in the  IFS  spe-
       cial  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	is  the	 name of the command whose arguments are being
       completed, the second argument is the word  being  completed,  and  the
       third  argument	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.

       Next,  any  command specified with the -C option is invoked in an envi-
       ronment 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	speci-
       fied  with  the -X option is applied to the list.  The filter is a pat-
       tern 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 match-
       ing 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 sup-
       plied  to complete when the compspec was defined, the bash default com-
       pletions 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	speci-
       fied  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


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 com-
       mands  (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 vari-
       able  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.	 When the his-
       tory 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 an inter-
       active shell exits, the last $HISTSIZE lines are copied from  the  his-
       tory 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 over-
       written.	 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 his-
       tory lines.  After saving the history, the history file is truncated to
       contain no more than HISTFILESIZE lines.	 If HISTFILESIZE is  not  set,
       no truncation is performed.

       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 his-
       tory  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 com-
       mand (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 read-
       ing  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 fol-
       lowing 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  his-
       tory timestamps when writing the history file.

   Event Designators
       An  event designator is a reference to a command line entry in the his-
       tory 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 postition
	      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	 sepa-
       rated 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 argument.
       %      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 file name component, leaving only the head.
       t      Remove all leading file name 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  sin-
	      gle  backslash  will  quote the &.  If old is null, it is set to
	      the last old substituted, or, if no previous  history  substitu-
	      tions 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 -	 with-
       out  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  exe-
	      cuted from filename.  If filename does not contain a slash, file
	      names in PATH are used to find the  directory  containing	 file-
	      name.   The  file	 searched  for in PATH need not be executable.
	      When bash is  not	 in  posix  mode,  the	current	 directory  is
	      searched	if no file is found in PATH.  If the sourcepath option
	      to the shopt builtin command is turned  off,  the	 PATH  is  not
	      searched.	  If any arguments are supplied, they become the posi-
	      tional 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 sup-
	      plied, the name and  value  of  the  alias  is  printed.	 Alias
	      returns  true unless a name is given for which no alias has been
	      defined.

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

       bind [-m keymap] [-lpsvPSV]
       bind [-m keymap] [-q function] [-u function] [-r keyseq]
       bind [-m keymap] -f filename
       bind [-m keymap] -x keyseq:shell-command
       bind [-m keymap] keyseq:function-name
       bind readline-command
	      Display  current	readline key and function bindings, bind a key
	      sequence to a readline function or  macro,  or  set  a  readline
	      variable.	  Each	non-option  argument  is a command as it would
	      appear in .inputrc, but each binding or command must  be	passed
	      as  a  separate argument; e.g., '"\C-x\C-r": re-read-init-file'.
	      Options, if supplied, have the following meanings:
	      -m keymap
		     Use keymap as the keymap to be affected by the subsequent
		     bindings.	Acceptable keymap names are emacs, emacs-stan-
		     dard, emacs-meta, emacs-ctlx,  vi,	 vi-move,  vi-command,
		     and  vi-insert.  vi is equivalent to vi-command; 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 read-
		     line line buffer and the READLINE_POINT variable  to  the
		     current location of the insertion point.  If the executed
		     command changes  the  value  of  READLINE_LINE  or	 READ-
		     LINE_POINT,  those	 new  values  will be reflected in the
		     editing state.

	      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 non-zero when n is <= 0; Otherwise,
	      break returns 0 value.

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

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

       cd [-L|[-P [-e]]] [dir]
	      Change the current directory to dir.  The variable HOME  is  the
	      default  dir.   The  variable CDPATH defines the search path for
	      the directory containing 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 says to use the physical directory structure  instead  of
	      following	 symbolic  links  (see	also  the -P option to the set
	      builtin command); the -L option forces symbolic links to be fol-
	      lowed.   If  the	-e option is supplied with -P, and the current
	      working directory cannot be successfully determined after a suc-
	      cessful directory change, cd will return an unsuccessful status.
	      An argument of - is  equivalent  to  $OLDPWD.   If  a  non-empty
	      directory	 name  from CDPATH is used, or if - is the first argu-
	      ment, and the directory change is successful, the absolute path-
	      name  of	the  new  working directory is written to the standard
	      output.  The return value is true if the directory was  success-
	      fully 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 file name
	      used to invoke command to be displayed; the -V option produces a
	      more  verbose  description.  If the -V or -v option is supplied,
	      the exit status is 0 if command was found, and  1	 if  not.   If
	      neither option is supplied and an error occurred or command can-
	      not be found, the exit status is 127.  Otherwise, the exit  sta-
	      tus of the command builtin is the exit status of command.

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

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

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

       complete [-abcdefgjksuv] [-o comp-option] [-DE] [-A action]  [-G	 glob-
       pat] [-W wordlist] [-F function] [-C command]
	      [-X filterpat] [-P prefix] [-S suffix] name [name ...]
       complete -pr [-DE] [name ...]
	      Specify  how arguments to each name should be completed.	If the
	      -p option is supplied, or if no options are  supplied,  existing
	      completion  specifications are printed in a way that allows them
	      to be reused as input.  The -r option removes a completion spec-
	      ification	 for each name, or, if no names are supplied, all com-
	      pletion  specifications.	 The  -D  option  indicates  that  the
	      remaining	 options  and  actions should apply to the ``default''
	      command completion; that is, completion attempted on  a  command
	      for  which  no  completion  has previously been defined.	The -E
	      option indicates that the remaining options and  actions	should
	      apply  to	 ``empty''  command  completion;  that	is, completion
	      attempted on a blank line.

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

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

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

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

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

       continue [n]
	      Resume the next iteration of the enclosing for, while, until, or
	      select loop.  If n is specified, resume  at  the	nth  enclosing
	      loop.   n	 must  be  >=  1.   If n is greater than the number of
	      enclosing loops, the  last  enclosing  loop  (the	 ``top-level''
	      loop) is resumed.	 When continue is executed inside of loop, the
	      return value is non-zero when n is  <=  0;  Otherwise,  continue
	      returns  0 value. When continue is executed outside of loop, the
	      return value is 0.

       declare [-aAfFgilrtux] [-p] [name[=value] ...]
       typeset [-aAfFgilrtux] [-p] [name[=value] ...]
	      Declare variables and/or give them attributes.  If no names  are
	      given  then display the values of variables.  The -p option will
	      display the attributes and values of each name.  When -p is used
	      with name arguments, additional options are ignored.  When -p is
	      supplied without name arguments, it will display the  attributes
	      and  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 defi-
	      nitions; 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 dis-
	      played 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 evalua-
		     tion  (see ARITHMETIC EVALUATION above) is performed when
		     the variable is assigned a value.
	      -l     When the variable is assigned  a  value,  all  upper-case
		     characters	 are  converted to lower-case.	The upper-case
		     attribute is disabled.
	      -r     Make names readonly.  These names cannot then be assigned
		     values by subsequent assignment statements or unset.
	      -t     Give  each	 name  the  trace attribute.  Traced functions
		     inherit the DEBUG	and  RETURN  traps  from  the  calling
		     shell.   The  trace  attribute has no special meaning for
		     variables.
	      -u     When the variable is assigned  a  value,  all  lower-case
		     characters	 are  converted to upper-case.	The lower-case
		     attribute is disabled.
	      -x     Mark names for export  to	subsequent  commands  via  the
		     environment.

	      Using  `+'  instead of `-' turns off the attribute instead, with
	      the exceptions that +a may not be used to destroy an array vari-
	      able  and	 +r will not remove the readonly attribute.  When used
	      in a function, makes 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.   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 [+n] [-n] [-clpv]
	      Without  options,	 displays  the	list  of  currently remembered
	      directories.  The default display	 is  on	 a  single  line  with
	      directory	 names	separated by spaces.  Directories are added to
	      the list with  the  pushd	 command;  the	popd  command  removes
	      entries from the list.
	      +n     Displays the nth entry counting from the left of the list
		     shown by dirs when invoked without options, starting with
		     zero.
	      -n     Displays  the  nth	 entry	counting from the right of the
		     list shown by dirs when invoked without options, starting
		     with zero.
	      -c     Clears  the  directory  stack  by	deleting  all  of  the
		     entries.
	      -l     Produces a longer listing;	 the  default  listing	format
		     uses a tilde to denote the home directory.
	      -p     Print the directory stack with one entry per line.
	      -v     Print  the	 directory stack with one entry per line, pre-
		     fixing each entry with its index in the stack.

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

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

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

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

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

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

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

       export [-fn] [name[=word]] ...
       export -p
	      The  supplied names are marked for automatic export to the envi-
	      ronment of subsequently executed commands.  If the -f option  is
	      given,  the names refer to functions.  If no names are given, or
	      if the -p option is supplied, a  list  of	 all  names  that  are
	      exported	in  this  shell	 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 func-
	      tion.

       fc [-e ename] [-lnr] [first] [last]
       fc -s [pat=rep] [cmd]
	      Fix  Command.  In the first form, a range of commands from first
	      to last is selected from the history list.  First and  last  may
	      be  specified  as a string (to locate the last command beginning
	      with that string) or as a number	(an  index  into  the  history
	      list, where a negative number is used as an offset from the cur-
	      rent 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 spec-
	      ified  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.	Other-
	      wise,  the editor given by ename is invoked on a file containing
	      those commands.  If ename is not given, the value of the	FCEDIT
	      variable	is used, and the value of EDITOR if FCEDIT is not set.
	      If neither variable is set, vi is used.  When  editing  is  com-
	      plete, the edited commands are echoed and executed.

	      In  the  second form, command is re-executed after each instance
	      of pat is replaced by rep.  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 com-
	      mand.

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

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

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

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

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

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

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

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

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

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

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

	      The return status is 0 unless no command matches pattern.

       history [n]
       history -c
       history -d offset
       history -anrw [filename]
       history -p arg [arg ...]
       history -s arg [arg ...]
	      With no options, display the command history list with line num-
	      bers.  Lines listed with a * have been modified.	An argument of
	      n	 lists only the last n lines.  If the shell variable HISTTIME-
	      FORMAT is set and not null, it is used as a  format  string  for
	      strftime(3)  to display the time stamp associated with each dis-
	      played history entry.  No intervening blank is  printed  between
	      the  formatted  time stamp and the history line.	If filename is
	      supplied, it is used as the name of the history  file;  if  not,
	      the  value  of HISTFILE is used.	Options, if supplied, have the
	      following meanings:
	      -c     Clear the history list by deleting all the entries.
	      -d offset
		     Delete the history entry at position offset.
	      -a     Append the ``new'' history lines (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 use them as the
		     current history.
	      -w     Write the current history to the history file,  overwrit-
		     ing the history file's contents.
	      -p     Perform  history  substitution  on the following args and
		     display the result on  the	 standard  output.   Does  not
		     store  the results in the history list.  Each arg must be
		     quoted to disable normal history expansion.
	      -s     Store the args in the history list	 as  a	single	entry.
		     The  last	command	 in the history list is removed before
		     the args are added.

	      If the HISTTIMEFORMAT variable is set, the time  stamp  informa-
	      tion  associated	with each history entry is written to the his-
	      tory file, marked with the history comment character.  When  the
	      history  file  is read, lines beginning with the history comment
	      character followed immediately by a  digit  are  interpreted  as
	      timestamps for the 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 sup-
	      plied as an argument to -d, or the history expansion supplied as
	      an argument to -p fails.

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

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

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

       kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...
       kill -l [sigspec | exit_status]
	      Send the signal named by sigspec	or  signum  to	the  processes
	      named  by	 pid or 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 ARITH-
	      METIC EVALUATION above).	If the last arg evaluates  to  0,  let
	      returns 1; 0 is returned otherwise.

       local [option] [name[=value] ...]
	      For  each	 argument, a local variable named name is created, and
	      assigned value.  The option can be any of the  options  accepted
	      by declare.  When local is used within a function, it causes the
	      variable name to have a visible scope restricted to  that	 func-
	      tion and its children.  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 vari-
	      able array, or from file descriptor fd if the -u option is  sup-
	      plied.   The variable MAPFILE is the default array.  Options, if
	      supplied, have the following meanings:
	      -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	 stan-
		     dard input.
	      -C     Evaluate  callback each time quantum lines are read.  The
		     -c option specifies quantum.
	      -c     Specify the number of lines read  between	each  call  to
		     callback.

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

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

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

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

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

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

	      The  format  is a character string which contains three types of
	      objects: plain characters, which are simply copied  to  standard
	      output,  character  escape  sequences,  which  are converted and
	      copied to the standard output, and format	 specifications,  each
	      of  which	 causes	 printing of the next successive argument.  In
	      addition to the standard printf(1) format specifications, printf
	      interprets the following extensions:
	      %b     causes printf to expand backslash escape sequences in the
		     corresponding argument (except that \c terminates output,
		     backslashes  in \', \", and \? are not removed, and octal
		     escapes beginning with \0 may contain up to four digits).
	      %q     causes printf to output the corresponding argument	 in  a
		     format that can be reused as shell input.
	      %(datefmt)T
		     causes  printf  to	 output the date-time string resulting
		     from using datefmt as a format  string  for  strftime(3).
		     The corresponding argument is an integer representing the
		     number of seconds since the epoch.	 Two special  argument
		     values  may  be used: -1 represents the current time, and
		     -2 represents the time the shell was invoked.

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

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

       pushd [-n] [+n] [-n]
       pushd [-n] [dir]
	      Adds  a  directory to the top of the directory stack, or rotates
	      the stack, making the new top of the stack the  current  working
	      directory.  With no arguments, 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.

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

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

       read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p
       prompt] [-t timeout] [-u fd] [name ...]
	      One line is read from the	 standard  input,  or  from  the  file
	      descriptor  fd supplied as an argument to the -u option, 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 interven-
	      ing separators assigned to the last name.	 If  there  are	 fewer
	      words read from the input stream than names, the remaining names
	      are assigned empty values.  The characters in IFS	 are  used  to
	      split  the  line into words.  The backslash character (\) may be
	      used to remove any special meaning for the next  character  read
	      and  for line continuation.  Options, if supplied, have the fol-
	      lowing meanings:
	      -a aname
		     The words are assigned to sequential indices of the array
		     variable aname, starting at 0.  aname is unset before any
		     new  values  are  assigned.   Other  name	arguments  are
		     ignored.
	      -d delim
		     The  first	 character  of	delim is used to terminate the
		     input line, rather than newline.
	      -e     If the standard input is coming from a terminal, readline
		     (see  READLINE  above) is used to obtain the line.	 Read-
		     line uses the current (or default, if  line  editing  was
		     not previously active) editing settings.
	      -i text
		     If	 readline  is  being  used  to	read the line, text is
		     placed into the editing buffer before editing begins.
	      -n nchars
		     read returns after reading nchars characters rather  than
		     waiting  for a complete line of input, but honor a delim-
		     iter if fewer than nchars characters are read before  the
		     delimiter.
	      -N nchars
		     read  returns  after  reading  exactly  nchars characters
		     rather than waiting for a complete line of input,	unless
		     EOF  is encountered or read times out.  Delimiter charac-
		     ters encountered in the input are not  treated  specially
		     and  do  not cause read to return until nchars characters
		     are read.
	      -p prompt
		     Display prompt on standard error, without a trailing new-
		     line, before attempting to read any input.	 The prompt is
		     displayed only if input is coming from a terminal.
	      -r     Backslash does not act as an escape character.  The back-
		     slash  is considered to be part of the line.  In particu-
		     lar, a backslash-newline pair may not be used as  a  line
		     continuation.
	      -s     Silent mode.  If input is coming from a terminal, charac-
		     ters are not echoed.
	      -t timeout
		     Cause read to time out and return failure if  a  complete
		     line  of input is not read within timeout seconds.	 time-
		     out may be a decimal number  with	a  fractional  portion
		     following	the decimal point.  This option is only effec-
		     tive if read is reading input from a terminal,  pipe,  or
		     other  special  file;  it has no effect when reading from
		     regular files.  If timeout is 0, read returns success  if
		     input  is	available  on  the  specified file descriptor,
		     failure otherwise.	 The exit status is greater  than  128
		     if the timeout is exceeded.
	      -u fd  Read input from file descriptor fd.

	      If no names are supplied, the line read is assigned to the vari-
	      able REPLY.  The return code  is	zero,  unless  end-of-file  is
	      encountered,  read  times	 out (in which case the return code is
	      greater than 128), or an invalid file descriptor is 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 exit with the return value specified by n.
	      If n is omitted, the return status is that of the	 last  command
	      executed	in the function body.  If used outside a function, but
	      during execution of a script by  the  .	(source)  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 used outside a
	      function and not during execution of a script by .,  the	return
	      status is false.	Any command associated with the RETURN trap is
	      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 can-
	      not  be  reset.  In posix mode, only shell variables are listed.
	      The output is sorted according  to  the  current	locale.	  When
	      options  are specified, they set or unset shell attributes.  Any
	      arguments remaining after option processing are treated as  val-
	      ues for the positional parameters and are assigned, in order, to
	      $1, $2, ...  $n.	Options,  if  specified,  have	the  following
	      meanings:
	      -a      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 immedi-
		      ately, rather than before the next primary prompt.  This
		      is effective only when job control is enabled.
	      -e      Exit  immediately	 if a pipeline (which may consist of a
		      single simple command),  a subshell command enclosed  in
		      parentheses,  or one of the commands executed as part of
		      a command list enclosed by  braces  (see	SHELL  GRAMMAR
		      above) exits with a non-zero status.  The shell does not
		      exit if the 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 !.  A trap  on  ERR,
		      if set, is executed before the shell exits.  This option
		      applies to the shell environment and each subshell envi-
		      ronment  separately  (see	 COMMAND EXECUTION ENVIRONMENT
		      above), and may cause subshells to exit before executing
		      all the commands in the subshell.
	      -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).   Background  pro-
		      cesses  run  in a separate process group and a line con-
		      taining their exit status is printed upon their  comple-
		      tion.
	      -n      Read commands but do not execute them.  This may be used
		      to check a shell script  for  syntax  errors.   This  is
		      ignored by interactive shells.
	      -o option-name
		      The option-name can be one of the following:
		      allexport
			      Same as -a.
		      braceexpand
			      Same as -B.
		      emacs   Use  an  emacs-style command line editing inter-
			      face.  This is enabled by default when the shell
			      is interactive, unless the shell is started with
			      the --noediting option.  This also  affects  the
			      editing interface used for read -e.
		      errexit Same as -e.
		      errtrace
			      Same as -E.
		      functrace
			      Same as -T.
		      hashall Same as -h.
		      histexpand
			      Same as -H.
		      history Enable command history, as described above under
			      HISTORY.	This option is on by default in inter-
			      active shells.
		      ignoreeof
			      The   effect   is	  as   if  the	shell  command
			      ``IGNOREEOF=10'' had been	 executed  (see	 Shell
			      Variables above).
		      keyword Same as -k.
		      monitor Same as -m.
		      noclobber
			      Same as -C.
		      noexec  Same as -n.
		      noglob  Same as -f.
		      nolog   Currently ignored.
		      notify  Same as -b.
		      nounset Same as -u.
		      onecmd  Same as -t.
		      physical
			      Same as -P.
		      pipefail
			      If  set,	the  return value of a pipeline is the
			      value of the last (rightmost)  command  to  exit
			      with  a non-zero status, or zero if all commands
			      in the pipeline exit successfully.  This	option
			      is disabled by default.
		      posix   Change  the  behavior  of bash where the default
			      operation differs from  the  POSIX  standard  to
			      match the standard (posix mode).
		      privileged
			      Same as -p.
		      verbose Same as -v.
		      vi      Use  a  vi-style command line editing interface.
			      This also affects the editing interface used for
			      read -e.
		      xtrace  Same as -x.
		      If -o is supplied with no option-name, the values of the
		      current options are printed.  If +o is supplied with  no
		      option-name,  a  series  of set commands to recreate the
		      current option settings is  displayed  on	 the  standard
		      output.
	      -p      Turn  on	privileged  mode.   In this mode, the $ENV and
		      $BASH_ENV files are not processed, shell	functions  are
		      not  inherited  from the environment, and the SHELLOPTS,
		      BASHOPTS, CDPATH,	 and  GLOBIGNORE  variables,  if  they
		      appear in the environment, are ignored.  If the shell is
		      started with the effective user (group) id not equal  to
		      the  real user (group) id, and the -p option is not sup-
		      plied, these actions are taken and the effective user id
		      is  set  to  the real user id.  If the -p option is sup-
		      plied at startup, the effective user id  is  not	reset.
		      Turning  this  option  off causes the effective user and
		      group ids to be set to the real user and group ids.
	      -t      Exit after reading and executing one command.
	      -u      Treat unset variables and parameters other than the spe-
		      cial  parameters "@" and "*" as an error when performing
		      parameter expansion.  If expansion is  attempted	on  an
		      unset  variable  or parameter, the shell prints an error
		      message, and, if not interactive, exits with a  non-zero
		      status.
	      -v      Print shell input lines as they are read.
	      -x      After  expanding	each simple command, for command, case
		      command, select command, or arithmetic for command, dis-
		      play  the expanded value of PS4, followed by the command
		      and its expanded arguments or associated word list.
	      -B      The shell performs brace expansion (see Brace  Expansion
		      above).  This is on by default.
	      -C      If  set,	bash  does not overwrite an existing file with
		      the >, >&, and <> redirection operators.	 This  may  be
		      overridden when creating output files by using the redi-
		      rection operator >| instead of >.
	      -E      If set, any trap on ERR is inherited by shell functions,
		      command  substitutions,  and commands executed in a sub-
		      shell environment.  The ERR trap is normally not	inher-
		      ited in such cases.
	      -H      Enable !	style history substitution.  This option is on
		      by default when the shell is interactive.
	      -P      If set, the shell does not follow	 symbolic  links  when
		      executing	 commands  such	 as cd that change the current
		      working  directory.   It	uses  the  physical  directory
		      structure instead.  By default, bash follows the logical
		      chain of	directories  when  performing  commands	 which
		      change the current directory.
	      -T      If  set,	any traps on DEBUG and RETURN are inherited by
		      shell functions,	command	 substitutions,	 and  commands
		      executed	in  a  subshell	 environment.	The  DEBUG and
		      RETURN traps are normally not inherited in such cases.
	      --      If no arguments follow this option, then the  positional
		      parameters are unset.  Otherwise, the positional parame-
		      ters are set to the args, even if	 some  of  them	 begin
		      with a -.
	      -	      Signal  the  end of options, cause all remaining args to
		      be assigned to the positional parameters.	 The -x and -v
		      options are turned off.  If there are no args, the posi-
		      tional parameters remain unchanged.

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

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

       shopt [-pqsu] [-o] [optname ...]
	      Toggle the values of variables controlling optional shell behav-
	      ior.  With no options, or with the -p option, a list of all set-
	      table 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 fol-
	      lowing meanings:
	      -s     Enable (set) each optname.
	      -u     Disable (unset) each optname.
	      -q     Suppresses normal output (quiet mode); the return	status
		     indicates whether the optname is set or unset.  If multi-
		     ple optname arguments are given with -q, the return  sta-
		     tus  is zero if all optnames are enabled; non-zero other-
		     wise.
	      -o     Restricts the values of optname to be those  defined  for
		     the -o option to the set builtin.

	      If  either  -s or -u is used with no optname arguments, the dis-
	      play is limited to those options which are set or unset, respec-
	      tively.	Unless otherwise noted, the shopt options are disabled
	      (unset) by default.

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

	      The list of shopt options is:

	      autocd  If  set,	a command name that is the name of a directory
		      is executed as if it were the argument to	 the  cd  com-
		      mand.  This option is only used by interactive shells.
	      cdable_vars
		      If  set,	an  argument to the cd builtin command that is
		      not a directory is assumed to be the name of a  variable
		      whose value is the directory to change to.
	      cdspell If set, minor errors in the spelling of a directory com-
		      ponent in a cd command will be  corrected.   The	errors
		      checked for are transposed characters, a missing charac-
		      ter, and one character too many.	 If  a	correction  is
		      found,  the corrected file name is printed, and the com-
		      mand proceeds.  This option is only used by  interactive
		      shells.
	      checkhash
		      If set, bash checks that a command found in the hash ta-
		      ble exists before trying to execute  it.	 If  a	hashed
		      command  no  longer exists, a normal path search is per-
		      formed.
	      checkjobs
		      If set, bash lists the status of any stopped and running
		      jobs  before  exiting an interactive shell.  If any jobs
		      are running, this causes the exit to be deferred until a
		      second  exit is attempted without an intervening command
		      (see JOB CONTROL above).	 The  shell  always  postpones
		      exiting if any jobs are stopped.
	      checkwinsize
		      If  set,	bash checks the window size after each command
		      and, if necessary, updates the values of LINES and  COL-
		      UMNS.
	      cmdhist If  set,	bash attempts to save all lines of a multiple-
		      line command in the same	history	 entry.	  This	allows
		      easy re-editing of multi-line commands.
	      compat31
		      If set, bash changes its behavior to that of version 3.1
		      with respect to quoted arguments to the  [[  conditional
		      command's =~ operator.
	      compat32
		      If set, bash changes its behavior to that of version 3.2
		      with respect to locale-specific string  comparison  when
		      using  the  [[  conditional command's < and > operators.
		      Bash versions prior to bash-4.1 use ASCII collation  and
		      strcmp(3);  bash-4.1  and later use the current locale's
		      collation sequence and strcoll(3).
	      compat40
		      If set, bash changes its behavior to that of version 4.0
		      with  respect  to locale-specific string comparison when
		      using the [[ conditional command's  <  and  >  operators
		      (see  previous  item)  and  the effect of interrupting a
		      command list.
	      compat41
		      If set, bash, when in posix mode, treats a single	 quote
		      in  a  double-quoted  parameter  expansion  as a special
		      character.  The single quotes must match (an  even  num-
		      ber)  and	 the  characters between the single quotes are
		      considered quoted.  This is the behavior of  posix  mode
		      through  version 4.1.  The default bash behavior remains
		      as in previous versions.
	      direxpand
		      If set, bash replaces directory names with  the  results
		      of  word	expansion when performing filename completion.
		      This changes the contents of the readline	 editing  buf-
		      fer.   If	 not  set,  bash attempts to preserve what the
		      user typed.
	      dirspell
		      If set, bash attempts spelling correction	 on  directory
		      names  during word completion if the directory name ini-
		      tially supplied does not exist.
	      dotglob If set, bash includes filenames beginning with a `.'  in
		      the results of pathname expansion.
	      execfail
		      If set, a non-interactive shell will not exit if it can-
		      not execute the file specified as	 an  argument  to  the
		      exec  builtin  command.	An  interactive shell does not
		      exit if exec fails.
	      expand_aliases
		      If set, aliases are expanded as  described  above	 under
		      ALIASES.	This option is enabled by default for interac-
		      tive shells.
	      extdebug
		      If set,  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  sub-
			     routine  (a shell function or a shell script exe-
			     cuted 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  substitu-
			     tion, shell functions, and subshells invoked with
			     ( command ) inherit the DEBUG and RETURN traps.
		      6.     Error tracing is enabled:	command	 substitution,
			     shell  functions,	and  subshells	invoked with (
			     command ) inherit the ERR trap.
	      extglob If set, the extended pattern matching features described
		      above under Pathname Expansion are enabled.
	      extquote
		      If  set,	$'string'  and	$"string" quoting is performed
		      within  ${parameter}  expansions	enclosed   in	double
		      quotes.  This option is enabled by default.
	      failglob
		      If  set,	patterns  which fail to match filenames during
		      pathname expansion result in an expansion error.
	      force_fignore
		      If set, the suffixes  specified  by  the	FIGNORE	 shell
		      variable	cause words to be ignored when performing word
		      completion even if the ignored words are the only possi-
		      ble  completions.	  See  SHELL  VARIABLES	 above	for  a
		      description of  FIGNORE.	 This  option  is  enabled  by
		      default.
	      globstar
		      If set, the pattern ** used in a pathname expansion con-
		      text will match all files and zero or  more  directories
		      and  subdirectories.  If the pattern is followed by a /,
		      only directories and subdirectories match.
	      gnu_errfmt
		      If set, shell error messages are written in the standard
		      GNU error message format.
	      histappend
		      If  set,	the history list is appended to the file named
		      by the value of the HISTFILE  variable  when  the	 shell
		      exits, rather than overwriting the file.
	      histreedit
		      If  set, and readline is being used, a user is given the
		      opportunity to re-edit a failed history substitution.
	      histverify
		      If set, and readline is being used, the results of  his-
		      tory  substitution  are  not  immediately	 passed to the
		      shell parser.  Instead, the  resulting  line  is	loaded
		      into the readline editing buffer, allowing further modi-
		      fication.
	      hostcomplete
		      If set, and readline is being used, bash will attempt to
		      perform  hostname	 completion when a word containing a @
		      is  being	 completed  (see  Completing  under   READLINE
		      above).  This is enabled by default.
	      huponexit
		      If set, bash will send SIGHUP to all jobs when an inter-
		      active login shell exits.
	      interactive_comments
		      If set, allow a word beginning with # to cause that word
		      and  all remaining characters on that line to be ignored
		      in an interactive	 shell	(see  COMMENTS	above).	  This
		      option is enabled by default.
	      lastpipe
		      If  set,	and  job control is not active, the shell runs
		      the last command of a pipeline not executed in the back-
		      ground in the current shell environment.
	      lithist If  set,	and  the cmdhist option is enabled, multi-line
		      commands are saved to the history with embedded newlines
		      rather than using semicolon separators where possible.
	      login_shell
		      The  shell  sets this option if it is started as a login
		      shell (see INVOCATION above).   The  value  may  not  be
		      changed.
	      mailwarn
		      If  set,	and  a file that bash is checking for mail has
		      been accessed since the last time it  was	 checked,  the
		      message  ``The  mail in mailfile has been read'' is dis-
		      played.
	      no_empty_cmd_completion
		      If set, and  readline  is	 being	used,  bash  will  not
		      attempt to search the PATH for possible completions when
		      completion is attempted on an empty line.
	      nocaseglob
		      If set, bash matches  filenames  in  a  case-insensitive
		      fashion when performing pathname expansion (see Pathname
		      Expansion above).
	      nocasematch
		      If set, bash  matches  patterns  in  a  case-insensitive
		      fashion when performing matching while executing case or
		      [[ conditional commands.
	      nullglob
		      If set, bash allows patterns which match no  files  (see
		      Pathname	Expansion  above)  to expand to a null string,
		      rather than themselves.
	      progcomp
		      If set, the programmable completion facilities (see Pro-
		      grammable Completion above) are enabled.	This option is
		      enabled by default.
	      promptvars
		      If set, prompt strings undergo parameter expansion, com-
		      mand   substitution,  arithmetic	expansion,  and	 quote
		      removal after being expanded as described	 in  PROMPTING
		      above.  This option is enabled by default.
	      restricted_shell
		      The   shell  sets	 this  option  if  it  is  started  in
		      restricted mode (see RESTRICTED SHELL below).  The value
		      may  not be changed.  This is not reset when the startup
		      files are executed, allowing the startup files  to  dis-
		      cover whether or not a shell is restricted.
	      shift_verbose
		      If  set,	the shift builtin prints an error message when
		      the shift count exceeds the number of positional parame-
		      ters.
	      sourcepath
		      If set, the source (.) builtin uses the value of PATH to
		      find the directory containing the file  supplied	as  an
		      argument.	 This option is enabled by default.
	      xpg_echo
		      If   set,	 the  echo  builtin  expands  backslash-escape
		      sequences by default.

       suspend [-f]
	      Suspend the execution of this shell until it receives a  SIGCONT
	      signal. When the suspended shell is a background process, it can
	      be restarted by the fg command. For more information,  read  the
	      JOB  CONTROL  section.  The  suspend command can not suspend the
	      login shell. However, when -f option is specified, suspend  com-
	      mand  can	 suspend  even	login  shell.	The return status is 0
	      unless the shell is a login shell and -f is not supplied, or  if
	      job control is not enabled.

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

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

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

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

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

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

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

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

	      If a sigspec is ERR, the command arg is executed whenever a sim-
	      ple command has a non-zero exit status, subject to the following
	      conditions.  The ERR trap is not executed if the failed  command
	      is  part	of  the	 command list immediately following a while or
	      until keyword, part of the test in an if statement,  part	 of  a
	      command  executed in a && or || list, or if the command's return
	      value is being inverted via !.  These are	 the  same  conditions
	      obeyed by the errexit option.

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

       type [-aftpP] name [name ...]
	      With  no options, indicate how each name would be interpreted if
	      used as a command name.  If the -t option is used, type prints a
	      string  which  is	 one  of alias, keyword, function, builtin, or
	      file if  name  is	 an  alias,  shell  reserved  word,  function,
	      builtin,	or disk file, respectively.  If the name is not found,
	      then nothing  is	printed,  and  an  exit	 status	 of  false  is
	      returned.	  If  the  -p  option is used, type either returns the
	      name of the disk file that would be executed if name were speci-
	      fied as a command name, or nothing if ``type -t name'' would not
	      return file.  The -P option forces a PATH search for each	 name,
	      even if ``type -t name'' would not return file.  If a command is
	      hashed, -p and -P print the hashed value,	 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 func-
	      tion 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	speci-
	      fied, both the soft and hard limits are set.  The value of limit
	      can be a number in the unit specified for the resource or one of
	      the special values hard, soft, or unlimited, which stand for the
	      current hard limit,  the	current	 soft  limit,  and  no	limit,
	      respectively.   If  limit	 is  omitted, the current value of the
	      soft limit of the resource is printed, unless the -H  option  is
	      given.  When more than one resource is specified, the limit name
	      and unit are printed before the value.  Other options are inter-
	      preted as follows:
	      -a     All current limits are reported
	      -b     The maximum socket buffer size
	      -c     The maximum size of core files created
	      -d     The maximum size of a process's data segment
	      -e     The maximum scheduling priority ("nice")
	      -f     The  maximum  size	 of files written by the shell and its
		     children
	      -i     The maximum number of pending signals
	      -l     The maximum size that may be locked into memory
	      -m     The maximum resident set size (many systems do not	 honor
		     this limit)
	      -n     The maximum number of open file descriptors (most systems
		     do not allow this value to be set)
	      -p     The pipe size in 512-byte blocks (this may not be set)
	      -q     The maximum number of bytes in POSIX message queues
	      -r     The maximum real-time scheduling priority
	      -s     The maximum stack size
	      -t     The maximum amount of cpu time in seconds
	      -u     The maximum number of processes  available	 to  a	single
		     user
	      -v     The  maximum  amount  of  virtual memory available to the
		     shell and, on some systems, to its children
	      -x     The maximum number of file locks
	      -T     The maximum number of threads

	      If limit is given, it is the new value of the specified resource
	      (the -a option is display only).	If no option is given, then -f
	      is assumed.  Values are in 1024-byte increments, except for  -t,
	      which  is	 in seconds, -p, which is in units of 512-byte blocks,
	      and -T, -b, -n, and -u, which are unscaled values.   The	return
	      status is 0 unless an invalid option or argument is supplied, or
	      an error occurs while  setting  a	 new  limit.   In  POSIX  Mode
	      512-byte blocks are used for the `-c' and `-f' options.

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

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

       unset [-fv] [name ...]
	      For each name, remove the corresponding  variable	 or  function.
	      If no options are supplied, or the -v option is given, each name
	      refers to a shell variable.   Read-only  variables  may  not  be
	      unset.   If  -f  is specified, each name refers to a shell func-
	      tion, and the function definition is removed.  Each unset	 vari-
	      able  or function is removed from the environment passed to sub-
	      sequent commands.	 If any of COMP_WORDBREAKS,  RANDOM,  SECONDS,
	      LINENO,  HISTCMD,	 FUNCNAME, GROUPS, or DIRSTACK are unset, they
	      lose their special properties, even  if  they  are  subsequently
	      reset.  The exit status is true unless a name is readonly.

       wait [n ...]
	      Wait  for each specified process and return its termination sta-
	      tus.  Each n may be a process ID or a job	 specification;	 if  a
	      job  spec	 is  given,  all  processes in that job's pipeline are
	      waited for.  If n is not given, all currently active child  pro-
	      cesses  are  waited  for,	 and  the return status is zero.  If n
	      specifies a non-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:

       o      changing directories with cd

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

       o      specifying command names containing /

       o      specifying a file name containing a / as an argument  to	the  .
	      builtin command

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

       o      importing function definitions from  the	shell  environment  at
	      startup

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

       o      redirecting output using the >, >|, <>, >&, &>, and >> redirect-
	      ion operators

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

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

       o      using  the  enable  builtin  command  to	enable	disabled shell
	      builtins

       o      specifying the -p option to the command builtin command

       o      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 COM-
       MAND  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	Utili-
       ties, IEEE
       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.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	(from the source package) 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

       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.



GNU Bash-4.2		       2010 December 28			       BASH(1)