Provided by: bash_4.2-2ubuntu2_amd64 bug

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 incorporates useful features from the Korn and C
       shells (ksh and csh).

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

OPTIONS

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

       -c 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 subject to language translation when the
                 current locale is not C or POSIX.  This implies the -n option; no commands  will
                 be executed.
       [-+]O [shopt_option]
                 shopt_option  is  one  of  the  shell options accepted by the shopt builtin (see
                 SHELL BUILTIN COMMANDS below).  If shopt_option is present, -O sets the value of
                 that  option;  +O  unsets  it.   If  shopt_option is not supplied, the names and
                 values of the shell options accepted  by  shopt  are  printed  on  the  standard
                 output.   If  the  invocation  option is +O, the output is displayed in a format
                 that may be reused as input.
       --        A -- signals the end of options and disables  further  option  processing.   Any
                 arguments after the -- are treated as filenames and arguments.  An argument of -
                 is equivalent to --.

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

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

       --login
              Equivalent to -l.

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

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

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

       --posix
              Change  the  behavior  of  bash  where the default operation differs from the POSIX
              standard to match the standard (posix mode).

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

       --verbose
              Equivalent to  -v.

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

ARGUMENTS

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

INVOCATION

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

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

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

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

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

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

       When  bash  is started non-interactively, to run a shell script, for example, it looks for
       the variable BASH_ENV in the environment, expands its value if it appears there, and  uses
       the  expanded  value  as  the  name of a file to read and execute.  Bash behaves as if the
       following command were executed:
              if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
       but the value of the PATH variable is not used to search for the 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 interactive login shell, or a non-interactive shell  with  the  --login
       option,  it  first attempts to read and execute commands from /etc/profile and ~/.profile,
       in that order.  The --noprofile option may be used to inhibit this behavior.  When invoked
       as  an  interactive  shell  with the name sh, bash looks for the variable ENV, expands its
       value if it is defined, and uses the expanded value as the name of  a  file  to  read  and
       execute.   Since  a shell invoked as sh does not attempt to read and execute commands from
       any other startup files, the --rcfile option  has  no  effect.   A  non-interactive  shell
       invoked  with  the name sh does not attempt to read any other startup files.  When invoked
       as sh, bash enters posix mode after the startup files are read.

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

       Bash  attempts  to  determine  when it is being run with its standard input connected to a
       network connection, as when executed by the remote shell  daemon,  usually  rshd,  or  the
       secure  shell  daemon  sshd.  If bash determines it is being run in this fashion, it reads
       and executes commands from ~/.bashrc and ~/.bashrc, if these files exist and are readable.
       It  will  not  do  this  if  invoked as sh.  The --norc option may be used to inhibit this
       behavior, and the --rcfile option may be used to force another file to be read,  but  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 document.
       blank  A space or tab.
       word   A sequence of characters considered as a single unit by the shell.  Also known as a
              token.
       name   A  word  consisting  only of alphanumeric characters and underscores, and beginning
              with an alphabetic character or an underscore.  Also referred to as an identifier.
       metacharacter
              A character that, when unquoted, separates words.  One of the following:
              |  & ; ( ) < > space tab
       control operator
              A token that performs a control function.  It is one of the following symbols:
              || & && ; ;; ( ) | |& <newline>

RESERVED WORDS

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

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

SHELL GRAMMAR

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

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

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

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

       The standard output of command is connected via a pipe to the standard input of  command2.
       This  connection  is  performed  before  any  redirections  specified  by the command (see
       REDIRECTION below).  If |& is  used,  the  standard  error  of  command  is  connected  to
       command2's  standard  input  through  the pipe; it is shorthand for 2>&1 |.  This implicit
       redirection 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 successfully.  If the reserved word !  precedes a pipeline, the exit  status
       of that pipeline is the logical negation of the exit status as described above.  The shell
       waits for all commands in the pipeline to terminate before returning a value.

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

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

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

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

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

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

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

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

              command1 && command2

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

       An OR list has the form

              command1 || command2

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

   Compound Commands
       A compound command is one of the following:

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

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

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

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

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

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

       When the == and != operators are used,  the  string  to  the  right  of  the  operator  is
       considered  a  pattern  and  matched  according to the rules described below under Pattern
       Matching.  If the shell option nocasematch is enabled,  the  match  is  performed  without
       regard  to the case of alphabetic characters.  The return value is 0 if the string matches
       (==) or does not match (!=) the pattern, and 1 otherwise.  Any part of the pattern may  be
       quoted to force 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
       expression  and matched accordingly (as in regex(3)).  The return value is 0 if the string
       matches the pattern,  and  1  otherwise.   If  the  regular  expression  is  syntactically
       incorrect,  the  conditional  expression's  return  value  is  2.   If  the  shell  option
       nocasematch is enabled, the match is performed without regard to the  case  of  alphabetic
       characters.   Any part of the pattern may be quoted to force 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 parenthesized subexpression.

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

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

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

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

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

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

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

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

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

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

       The format for a coprocess is:

              coproc [NAME] command [redirections]

       This creates a coprocess named NAME.  If NAME is not supplied, the default name is COPROC.
       NAME  must  not  be  supplied if command is a simple command (see above); otherwise, it is
       interpreted as the first word of the simple command.  When the  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  compound  command  compound-command  (see Compound Commands
              above).  That command is usually a list of commands between { and }, but may be any
              command  listed  under  Compound  Commands  above.   compound-command  is  executed
              whenever name is specified as the name of a simple command.  Any redirections  (see
              REDIRECTION  below)  specified  when  a  function is defined are performed when the
              function is executed.  The exit status of a function definition is  zero  unless  a
              syntax error occurs or a readonly function with the same name already exists.  When
              executed, the exit status of a function is the exit  status  of  the  last  command
              executed in the body.  (See FUNCTIONS below.)

COMMENTS

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

QUOTING

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

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

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

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

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

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

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

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

       Words of the form $'string' are treated specially.   The  word  expands  to  string,  with
       backslash-escaped  characters  replaced  as  specified  by the ANSI C standard.  Backslash
       escape sequences, if present, are decoded as follows:
              \a     alert (bell)
              \b     backspace
              \e
              \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 number, or one of the
       special characters listed below under Special  Parameters.   A  variable  is  a  parameter
       denoted  by  a  name.  A variable has a value and zero or more attributes.  Attributes are
       assigned using the declare builtin command (see declare below in SHELL BUILTIN COMMANDS).

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

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

              name=[value]

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

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

   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 single word with the value of each parameter
              separated by the first character of the IFS special variable.   That  is,  "$*"  is
              equivalent  to  "$1c$2c...", where c is the first character of the value of the IFS
              variable.  If IFS is unset, the parameters are separated  by  spaces.   If  IFS  is
              null, the parameters are joined without intervening separators.
       @      Expands to the positional parameters, starting from one.  When the expansion occurs
              within double quotes, each parameter expands to a separate word.  That is, "$@"  is
              equivalent  to  "$1" "$2" ...  If the double-quoted expansion occurs within a word,
              the expansion of the first parameter is joined  with  the  beginning  part  of  the
              original word, and the expansion of the last parameter is joined with the last part
              of the original word.  When there are no positional parameters, "$@" and $@  expand
              to nothing (i.e., they are removed).
       #      Expands to the number of positional parameters in decimal.
       ?      Expands to the exit status of the most recently executed foreground pipeline.
       -      Expands  to  the  current  option  flags  as  specified upon invocation, by the set
              builtin command, or those set by the shell itself (such as the -i option).
       $      Expands to the process ID of the shell.  In  a  ()  subshell,  it  expands  to  the
              process ID of the current shell, not the subshell.
       !      Expands  to  the process ID of the most recently executed background (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 commands, $0 is set to the name
              of that file.  If bash is started with the -c option, then $0 is set to  the  first
              argument  after the string to be executed, if one is present.  Otherwise, it is set
              to the 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 environment or argument list.  Subsequently,
              expands to the last argument to the previous command, after expansion.  Also set to
              the  full  pathname  used  to  invoke  each  command  executed  and  placed  in the
              environment exported to that command.  When checking mail, this parameter holds the
              name of the mail file currently being checked.

   Shell Variables
       The following variables are set by the shell:

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

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

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

       BASH_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 completion 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  suffix  matches one of the entries in
              FIGNORE is excluded from the list of matched filenames.  A sample value  is  ".o:~"
              (Quoting is needed when assigning a value to this variable, which contains tildes).
       FUNCNEST
              If set to a numeric value greater than 0, defines a maximum function nesting level.
              Function invocations that exceed this nesting level will cause the current  command
              to abort.
       GLOBIGNORE
              A  colon-separated  list of patterns defining the set of filenames to be ignored by
              pathname expansion.  If a filename matched by a  pathname  expansion  pattern  also
              matches one of the patterns in GLOBIGNORE, it is removed from the list of matches.
       HISTCONTROL
              A  colon-separated list of values controlling how commands are saved on the history
              list.  If the list of values includes ignorespace, lines which begin with  a  space
              character  are  not  saved in the history list.  A value of ignoredups causes lines
              matching the previous history entry to not be saved.   A  value  of  ignoreboth  is
              shorthand for ignorespace and ignoredups.  A value of erasedups causes all previous
              lines matching the current line to be removed from the  history  list  before  that
              line  is  saved.   Any  value  not in the above list is ignored.  If HISTCONTROL is
              unset, or does not include a valid value, all lines read by the  shell  parser  are
              saved  on  the  history  list,  subject to the value of HISTIGNORE.  The second and
              subsequent lines of a multi-line compound command are not tested, and are added  to
              the history regardless of the value of HISTCONTROL.
       HISTFILE
              The  name  of  the file in which command history is saved (see HISTORY below).  The
              default value is ~/.bash_history.  If unset, the command history is not saved  when
              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 truncated,  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 complete line (no implicit `*' is appended).  Each pattern is
              tested against the line after the checks specified by HISTCONTROL are applied.   In
              addition  to the normal shell pattern matching characters, `&' matches the previous
              history line.  `&' may be escaped using  a  backslash;  the  backslash  is  removed
              before  attempting  a  match.   The  second  and  subsequent  lines of a multi-line
              compound command are not tested, and are added to the  history  regardless  of  the
              value of HISTIGNORE.
       HISTSIZE
              The number of commands to remember in the command history (see HISTORY below).  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  completions.   When  HOSTFILE  is  unset,  the hostname list is
              cleared.
       IFS    The Internal Field Separator that is used for word splitting after expansion and to
              split  lines  into  words  with  the  read  builtin  command.  The default value is
              ``<space><tab><newline>''.
       IGNOREEOF
              Controls the action of an interactive shell on receipt of an EOF character  as  the
              sole  input.   If  set, the value is the number of consecutive EOF characters which
              must be typed as the first characters on an input line before bash exits.   If  the
              variable  exists  but  does  not have a numeric value, or has no value, the default
              value is 10.  If it does not exist, EOF signifies the end of input to the shell.
       INPUTRC
              The filename for the readline startup file, overriding the  default  of  ~/.inputrc
              (see READLINE below).
       LANG   Used  to  determine  the locale category for any category not specifically selected
              with a variable starting with LC_.
       LC_ALL This variable overrides the value of LANG and any other LC_ variable  specifying  a
              locale category.
       LC_COLLATE
              This  variable  determines  the  collation  order  used when sorting the results of
              pathname expansion, and determines the behavior of range  expressions,  equivalence
              classes, and collating sequences within pathname expansion and pattern matching.
       LC_CTYPE
              This  variable  determines  the  interpretation  of  characters and the behavior of
              character classes within pathname expansion and pattern matching.
       LC_MESSAGES
              This variable  determines  the  locale  used  to  translate  double-quoted  strings
              preceded by a $.
       LC_NUMERIC
              This variable determines the locale category used for number formatting.
       LINES  Used  by  the  select  compound command to determine the column length for printing
              selection lists.  Automatically set upon receipt of a SIGWINCH.
       MAIL   If this parameter is set to a file or directory name and the MAILPATH  variable  is
              not  set,  bash  informs  the  user of the arrival of mail in the specified file or
              Maildir-format directory.
       MAILCHECK
              Specifies how often (in seconds) bash checks for mail.  The default is 60  seconds.
              When  it is time to check for mail, the shell does so before displaying the primary
              prompt.  If this variable is unset, or set to a value that is not a number  greater
              than or equal to zero, the shell disables mail checking.
       MAILPATH
              A  colon-separated  list  of  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 location of the user  mail
              files that it uses is system dependent (e.g., /var/mail/$USER).
       OPTERR If  set  to  the  value  1,  bash  displays error messages generated by the getopts
              builtin command (see SHELL BUILTIN COMMANDS below).  OPTERR  is  initialized  to  1
              each time the shell is invoked or a shell script is executed.
       PATH   The search path for commands.  It is a colon-separated list of directories in which
              the shell looks for commands (see COMMAND EXECUTION below).  A  zero-length  (null)
              directory  name  in  the  value  of  PATH  indicates the current directory.  A null
              directory name may appear as two adjacent colons, or  as  an  initial  or  trailing
              colon.   The  default path is system-dependent, and is set by the administrator who
              installs           bash.            A           common           value           is
              ``/usr/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  multiple  times,  as  necessary,  to  indicate  multiple  levels of
              indirection.  The default is ``+ ''.
       SHELL  The full pathname to the shell is kept in this environment variable.  If it is  not
              set  when  the  shell  starts,  bash assigns to it the full pathname of the current
              user's login shell.
       TIMEFORMAT
              The value of this parameter is used as a format string specifying  how  the  timing
              information for pipelines prefixed with the time reserved word should be displayed.
              The % character introduces an escape sequence that is expanded to a time  value  or
              other  information.   The  escape  sequences and their meanings are as follows; the
              braces denote optional portions.
              %%        A literal %.
              %[p][l]R  The elapsed time in seconds.
              %[p][l]U  The number of CPU seconds spent in user mode.
              %[p][l]S  The number of CPU seconds spent in system mode.
              %P        The CPU percentage, computed as (%U + %S) / %R.

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

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

              If  this  variable  is  not   set,   bash   acts   as   if   it   had   the   value
              $'\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 terminates if input does not arrive after
              TMOUT seconds when input is coming from a terminal.  In an interactive  shell,  the
              value  is  interpreted as the number of seconds to wait for 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 commands without redirections are treated
              as candidates for resumption of an existing stopped job.   There  is  no  ambiguity
              allowed;  if  there  is  more than one job beginning with the string typed, the job
              most recently accessed is selected.  The name of a stopped job, in this context, is
              the  command line used to start it.  If set to the value exact, the string supplied
              must match the name of a stopped job exactly;  if  set  to  substring,  the  string
              supplied  needs  to  match a substring of the name of a stopped job.  The substring
              value provides functionality analogous to the %?  job identifier (see  JOB  CONTROL
              below).   If  set  to  any  other  value, the supplied string must be a prefix of a
              stopped job's name; this  provides  functionality  analogous  to  the  %string  job
              identifier.
       histchars
              The  two  or three characters which control history expansion and tokenization (see
              HISTORY EXPANSION below).  The first character is the history expansion  character,
              the  character  which  signals the start of a history expansion, normally `!'.  The
              second character is the quick substitution character, which is  used  as  shorthand
              for re-running the previous command entered, substituting one string for another in
              the command.  The default is `^'.  The optional third character  is  the  character
              which indicates that the remainder of the line is a comment when found as the first
              character of a word, normally `#'.  The history comment  character  causes  history
              substitution  to  be  skipped  for  the  remaining  words on the line.  It does not
              necessarily cause the shell parser to treat the rest of the line as a comment.

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

       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 [subscript]=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; otherwise the index of the
       element assigned is the last index assigned to by the statement plus one.  Indexing starts
       at zero.

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

       This  syntax  is  also  accepted by the declare builtin.  Individual array elements may be
       assigned to using the name[subscript]=value syntax introduced above.

       Any element of an array may  be  referenced  using  ${name[subscript]}.   The  braces  are
       required  to  avoid  conflicts  with pathname expansion.  If subscript is @ or *, the word
       expands to all members of name.  These subscripts differ only when the word appears within
       double quotes.  If the word is double-quoted, ${name[*]} expands to a single word with the
       value of each array member separated by the first character of the IFS  special  variable,
       and  ${name[@]}  expands each element of name to a separate word.  When there are no array
       members, ${name[@]} expands to nothing.  If the double-quoted expansion  occurs  within  a
       word,  the  expansion  of  the  first  parameter  is joined with the beginning part of the
       original word, and the expansion of the last parameter is joined with the last part of the
       original  word.  This is analogous to the expansion of the special parameters * and @ (see
       Special   Parameters   above).    ${#name[subscript]}   expands   to   the    length    of
       ${name[subscript]}.   If  subscript  is * or @, the expansion is the number of elements in
       the array.  Referencing an array variable without a subscript is equivalent to referencing
       the array with a subscript of 0.

       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  substitution,  arithmetic  expansion,  word  splitting, and
       pathname expansion.

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

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

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

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

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

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

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

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

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

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

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

       Each  variable assignment is checked for unquoted tilde-prefixes immediately following a :
       or the first =.  In these cases, tilde expansion is also performed.  Consequently, one may
       use  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 variable; this variable is then expanded and that value is
       used in the rest of the substitution, rather than the value of parameter itself.  This  is
       known as indirect expansion.  The exceptions to this are the expansions of ${!prefix*} and
       ${!name[@]} described below.  The exclamation point must immediately follow the left brace
       in order to introduce indirection.

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

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

       ${parameter:-word}
              Use Default Values.  If parameter is unset  or  null,  the  expansion  of  word  is
              substituted.  Otherwise, the value of parameter is substituted.
       ${parameter:=word}
              Assign  Default  Values.   If  parameter is unset or null, the expansion of word is
              assigned to parameter.  The value of parameter  is  then  substituted.   Positional
              parameters and special parameters may not be assigned to in this way.
       ${parameter:?word}
              Display  Error  if  Null or Unset.  If parameter is null or unset, the expansion of
              word (or a message to that effect if  word  is  not  present)  is  written  to  the
              standard  error  and  the  shell,  if it is not interactive, exits.  Otherwise, the
              value of parameter is substituted.
       ${parameter:+word}
              Use Alternate Value.  If parameter  is  null  or  unset,  nothing  is  substituted,
              otherwise the expansion of word is substituted.
       ${parameter:offset}
       ${parameter:offset:length}
              Substring  Expansion.   Expands to up to length characters of parameter starting at
              the character specified by offset.  If length is omitted, expands to the  substring
              of  parameter starting 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.   Arithmetic  expressions  starting  with  a  -  must  be  separated  by
              whitespace  from  the  preceding  : to be distinguished from the Use Default Values
              expansion.  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 number of characters, and the expansion
              is the characters between the two offsets.  If parameter is @, the result is length
              positional 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
              maximum   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 prefixed to the list.

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

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

       ${#parameter}
              Parameter  length.   The  length  in  characters  of  the  value  of  parameter  is
              substituted.   If  parameter  is  *  or  @,  the value substituted is the number of
              positional parameters.  If parameter is an array name subscripted by *  or  @,  the
              value substituted is the number of elements in the array.

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

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

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

       ${parameter^pattern}
       ${parameter^^pattern}
       ${parameter,pattern}
       ${parameter,,pattern}
              Case modification.  This expansion modifies the case of  alphabetic  characters  in
              parameter.   The  pattern  is  expanded  to  produce  a pattern just as in pathname
              expansion.   The  ^  operator  converts  lowercase  letters  matching  pattern   to
              uppercase; the , operator converts matching uppercase letters to lowercase.  The ^^
              and ,, expansions convert each matched character in the expanded value; the ^ and ,
              expansions  match  and  convert only the first character in the expanded value.  If
              pattern is omitted, it is treated like a ?,  which  matches  every  character.   If
              parameter  is @ or *, the case modification operation is applied to each positional
              parameter in turn, and the expansion is the resultant list.   If  parameter  is  an
              array  variable subscripted with @ or *, the case modification operation is applied
              to each member of the array in turn, and the expansion is the resultant list.

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

              $(command)
       or
              `command`

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

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

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

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

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

              $((expression))

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

       The  expression  is  treated as if it were within double quotes, but a double quote inside
       the parentheses is not treated specially.  All tokens in the expression undergo  parameter
       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 output connected to a FIFO or some file in  /dev/fd.
       The name of this file is passed as an argument to the current command as the result of the
       expansion.  If the >(list) form is used, writing to the file will provide input for  list.
       If  the  <(list) form is used, the file passed as an argument should be read to obtain the
       output of list.

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

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

       The shell treats each character of IFS as a delimiter, and splits the results of the other
       expansions  into  words  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  alphabetic
       characters.  Note that when using range expressions like [a-z] (see below), letters of the
       other case may be included, depending on the setting of LC_COLLATE.   When  a  pattern  is
       used  for  pathname  expansion, the character ``.''  at the start of a name or immediately
       following a slash must be matched explicitly, unless the  shell  option  dotglob  is  set.
       When matching a pathname, the slash character must always be matched explicitly.  In other
       cases, the ``.''  character is not treated specially.  See the description of shopt  below
       under  SHELL BUILTIN COMMANDS for a description of the nocaseglob, nullglob, failglob, and
       dotglob shell options.

       The GLOBIGNORE shell variable may be used to restrict the set of  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
       GLOBIGNORE 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 subdirectories.
              ?      Matches any single character.
              [...]  Matches  any one of the enclosed characters.  A pair of characters separated
                     by a hyphen denotes a range expression; any  character  that  sorts  between
                     those  two  characters,  inclusive,  using  the  current  locale's collating
                     sequence and character set, is matched.  If the  first  character  following
                     the  [  is  a  !   or  a  ^ then any character not enclosed is matched.  The
                     sorting order of characters  in  range  expressions  is  determined  by  the
                     current  locale and the 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 including it as the first character in the set.

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

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

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

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

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

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

REDIRECTION

       Before  a  command  is  executed,  its  input and output may be redirected using a special
       notation interpreted by the shell.  Redirection 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 omitted, and the first
       character of the redirection operator is <, the redirection refers to the  standard  input
       (file  descriptor  0).   If  the  first  character  of  the redirection operator is >, the
       redirection refers to the standard output (file descriptor 1).

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

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

              ls > dirlist 2>&1

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

              ls 2>&1 > dirlist

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

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

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

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

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

       The general format for redirecting input is:

              [n]<word

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

       The general format for redirecting output is:

              [n]>word

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

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

       The general format for appending output is:

              [n]>>word

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

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

              &>word
       and
              >&word

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

              >word 2>&1

   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, command
       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 evaluates to -, file descriptor n is closed.  If n is  not  specified,  the  standard
       input (file descriptor 0) is used.

       The operator

              [n]>&word

       is  used  similarly  to  duplicate  output  file  descriptors.  If n is not specified, the
       standard output (file descriptor 1) is used.  If the digits in word do not specify a  file
       descriptor  open  for  output,  a  redirection  error  occurs.  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 compound command.  As
       a consequence, aliases defined in a function are not available until after  that  function
       is  executed.  To be safe, always put alias definitions on a separate line, and do not use
       alias in compound commands.

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

FUNCTIONS

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

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

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

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

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

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

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

ARITHMETIC EVALUATION

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

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

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

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

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

CONDITIONAL EXPRESSIONS

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

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

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

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

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

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

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

COMMAND EXECUTION

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

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

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

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

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

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

COMMAND EXECUTION ENVIRONMENT

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

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

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

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

       ·      current traps set by trap

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

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

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

       ·      options enabled by shopt

       ·      shell aliases defined with alias

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

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

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

       ·      the current working directory

       ·      the file creation mode mask

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

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

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

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

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

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

ENVIRONMENT

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

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

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

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

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

EXIT STATUS

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

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

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

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

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

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

SIGNALS

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

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

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

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

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

JOB CONTROL

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

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

              [1] 25647

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

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

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

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

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

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

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

PROMPTING

       When executing interactively, bash displays the primary prompt PS1 when  it  is  ready  to
       read  a  command,  and  the  secondary  prompt  PS2 when it needs more input to complete a
       command.  Bash allows these prompt strings to be  customized  by  inserting  a  number  of
       backslash-escaped special characters that are decoded as follows:
              \a     an ASCII bell character (07)
              \d     the date in "Weekday Month Date" format (e.g., "Tue May 26")
              \D{format}
                     the  format  is  passed  to  strftime(3) and the result is inserted into the
                     prompt  string;  an  empty  format  results  in   a   locale-specific   time
                     representation.  The braces are required
              \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 variable)
              \W     the basename of the current working directory, with $HOME abbreviated with a
                     tilde
              \!     the history number of this command
              \#     the command number of this command
              \$     if the effective UID is 0, a #, otherwise a $
              \nnn   the character corresponding to the octal number nnn
              \\     a backslash
              \[     begin a sequence of non-printing characters, which could be used to embed  a
                     terminal control sequence into the prompt
              \]     end a sequence of non-printing characters

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

READLINE

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

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

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

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

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

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

       For example, placing

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

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

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

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

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

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

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

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

              "\C-u": universal-argument
              "\C-x\C-r": re-read-init-file
              "\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 function name.  In the macro body, the
       backslash escapes described above are expanded.  Backslash will quote any other  character
       in the macro text, including " and '.

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

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

              set variable-name value

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

       bell-style (audible)
              Controls  what  happens  when  readline wants to ring the terminal bell.  If set to
              none, readline never rings the bell.  If set to visible, readline  uses  a  visible
              bell  if  one  is  available.   If  set  to  audible, readline attempts to ring the
              terminal's bell.
       bind-tty-special-chars (On)
              If set to On, readline attempts to bind the control characters treated specially by
              the kernel's terminal driver to their readline equivalents.
       comment-begin (``#'')
              The  string  that is inserted when the readline insert-comment command is executed.
              This command is bound to M-# in emacs mode and to # in vi command mode.
       completion-ignore-case (Off)
              If  set  to  On,  readline  performs  filename  matching  and   completion   in   a
              case-insensitive fashion.
       completion-prefix-display-length (0)
              The  length  in  characters  of the common prefix of a list of possible completions
              that is displayed without modification.  When set to a  value  greater  than  zero,
              common  prefixes  longer  than  this  value  are  replaced  with  an  ellipsis when
              displaying possible completions.
       completion-query-items (100)
              This determines when the user is queried  about  viewing  the  number  of  possible
              completions  generated  by  the possible-completions command.  It may be set to any
              integer value greater than or equal to zero.  If the number of possible completions
              is  greater  than or equal to the value of this variable, the user is asked whether
              or not he wishes to view them; otherwise they are simply listed on the terminal.
       convert-meta (On)
              If set to On, readline will convert characters with the eighth bit set to an  ASCII
              key  sequence  by  stripping  the  eighth bit and prefixing an escape character (in
              effect, using escape as the meta prefix).
       disable-completion (Off)
              If set to On, readline will inhibit word completion.  Completion characters will be
              inserted into the line as if they had been mapped to self-insert.
       editing-mode (emacs)
              Controls whether readline begins with a set of key bindings similar to Emacs or vi.
              editing-mode can be set to either emacs or vi.
       echo-control-characters (On)
              When set to On, on operating systems that indicate they support it, readline echoes
              a character corresponding to a signal generated from the keyboard.
       enable-keypad (Off)
              When  set  to  On,  readline  will  try to enable the application keypad when it is
              called.  Some systems need this to enable the arrow keys.
       enable-meta-key (On)
              When set to On, readline will try to enable any  meta  modifier  key  the  terminal
              claims  to  support  when it is called.  On many terminals, the meta key is used to
              send eight-bit characters.
       expand-tilde (Off)
              If set to On, tilde expansion is performed when readline attempts word completion.
       history-preserve-point (Off)
              If set to On, the history code attempts to place point at the same location on each
              history line retrieved with previous-history or next-history.
       history-size (0)
              Set  the  maximum  number  of history entries saved in the history list.  If set to
              zero, 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 command.  If this variable has not been
              given a value, the characters ESC and C-J will terminate an incremental search.
       keymap (emacs)
              Set the current  readline  keymap.   The  set  of  valid  keymap  names  is  emacs,
              emacs-standard,  emacs-meta,  emacs-ctlx,  vi,  vi-command,  and  vi-insert.  vi is
              equivalent to vi-command; emacs is equivalent to emacs-standard.  The default value
              is emacs; the value of editing-mode also affects the default keymap.
       mark-directories (On)
              If set to On, completed directory names have a slash appended.
       mark-modified-lines (Off)
              If  set to On, history lines that have been modified are displayed with a preceding
              asterisk (*).
       mark-symlinked-directories (Off)
              If set to On, completed names which are symbolic links to directories have a  slash
              appended (subject to the value of mark-directories).
       match-hidden-files (On)
              This  variable,  when  set  to On, causes readline to match files whose names begin
              with a `.' (hidden files) when performing filename completion.  If set to Off,  the
              leading `.' must be supplied by the user in the filename to be completed.
       menu-complete-display-prefix (Off)
              If  set  to  On, menu completion displays the common prefix of the list of possible
              completions (which may be empty) before cycling through the list.
       output-meta (Off)
              If set to On, readline will display characters with the  eighth  bit  set  directly
              rather than as a meta-prefixed escape sequence.
       page-completions (On)
              If  set  to On, readline uses an internal more-like pager to display a screenful of
              possible completions at a time.
       print-completions-horizontally (Off)
              If set to On, readline will display completions with matches sorted horizontally in
              alphabetical order, rather than down the screen.
       revert-all-at-newline (Off)
              If set to On, readline will undo all changes to history lines before returning when
              accept-line is executed.  By default, history lines  may  be  modified  and  retain
              individual undo lists across calls to readline.
       show-all-if-ambiguous (Off)
              This  alters the default behavior of the completion functions.  If set to On, words
              which have more than one  possible  completion  cause  the  matches  to  be  listed
              immediately instead of ringing the bell.
       show-all-if-unmodified (Off)
              This  alters  the default behavior of the completion functions in a fashion similar
              to show-all-if-ambiguous.  If set to On, words which have more  than  one  possible
              completion  without any possible partial completion (the possible completions don't
              share a common prefix) cause the  matches  to  be  listed  immediately  instead  of
              ringing the bell.
       skip-completed-text (Off)
              If  set  to On, this alters the default completion behavior when inserting a single
              match into the line.  It's only active when performing completion in the middle  of
              a  word.   If enabled, readline does not insert characters from the completion that
              match characters after point in the word being completed, so portions of  the  word
              following the cursor are not duplicated.
       visible-stats (Off)
              If set to On, a character denoting a file's type as reported by stat(2) is appended
              to the filename when listing possible completions.

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

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

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

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

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

                     $if Bash
                     # Quote the current or previous word
                     "\C-xq": "\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  following  directive  would  read
              /etc/inputrc:

              $include  /etc/inputrc

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

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

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

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

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

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

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

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

   Commands for Changing Text
       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 cursor is deleted.
       quoted-insert (C-q, C-v)
              Add  the  next  character  typed  to  the  line  verbatim.   This  is how to insert
              characters like C-q, for example.
       tab-insert (C-v TAB)
              Insert a tab character.
       self-insert (a, b, A, 1, !, ...)
              Insert the character typed.
       transpose-chars (C-t)
              Drag the character before point forward over the character at point,  moving  point
              forward  as well.  If point is at the end of the line, then this transposes the two
              characters before point.  Negative arguments have no effect.
       transpose-words (M-t)
              Drag the word before point past the word after point, moving point over  that  word
              as well.  If point is at the end of the line, this transposes the last two words on
              the line.
       upcase-word (M-u)
              Uppercase the current (or following) word.  With a negative argument, uppercase the
              previous word, but do not move point.
       downcase-word (M-l)
              Lowercase the current (or following) word.  With a negative argument, lowercase the
              previous word, but do not move point.
       capitalize-word (M-c)
              Capitalize the current (or following) word.  With a negative  argument,  capitalize
              the previous word, but do not move point.
       overwrite-mode
              Toggle  overwrite  mode.   With  an explicit positive numeric argument, switches to
              overwrite mode.  With an explicit non-positive numeric argument, switches to insert
              mode.   This  command  affects only emacs mode; vi mode does overwrite differently.
              Each call to readline() starts in insert mode.  In overwrite mode, characters bound
              to self-insert replace the text at point rather than pushing the text to the right.
              Characters bound to backward-delete-char replace the character before point with  a
              space.  By default, this command is unbound.

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

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

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

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

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

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

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

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

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

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

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

       After  these matches have been generated, any shell function or command specified with the
       -F and -C options is invoked.  When the command or function  is  invoked,  the  COMP_LINE,
       COMP_POINT, COMP_KEY, and COMP_TYPE variables are assigned values as described above under
       Shell Variables.  If a shell function is being  invoked,  the  COMP_WORDS  and  COMP_CWORD
       variables  are  also  set.  When the function or command is invoked, the first argument 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 environment equivalent  to
       command  substitution.   It  should  print  a  list  of  completions, one per line, to the
       standard output.  Backslash may be used to escape a newline, if necessary.

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

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

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

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

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

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

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

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

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

HISTORY

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

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

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

HISTORY EXPANSION

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

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

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

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

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

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

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

       !      Start  a  history  substitution, except when followed by a blank, newline, carriage
              return, = or ( (when the extglob shell option is enabled using the shopt builtin).
       !n     Refer to command line n.
       !-n    Refer to the current command minus n.
       !!     Refer to the previous command.  This is a synonym for `!-1'.
       !string
              Refer to the most recent command preceding the current position in the history list
              starting with string.
       !?string[?]
              Refer  to  the  most  recent command preceding the current 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 separated
       by single spaces.

       0 (zero)
              The zeroth word.  For the shell, this is the command word.
       n      The nth word.
       ^      The first argument.  That is, word 1.
       $      The last 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 single backslash
              will quote the &.  If old is null, it is set to the last old substituted, or, if no
              previous  history  substitutions  took  place,  the  last  string  in a !?string[?]
              search.
       &      Repeat the previous substitution.
       g      Cause changes to  be  applied  over  the  entire  event  line.   This  is  used  in
              conjunction  with  `:s'  (e.g.,  `:gs/old/new/')  or  `:&'.  If used with `:s', any
              delimiter can be used in place of /, and the final delimiter is optional if  it  is
              the last character of the event line.  An a may be used as a synonym for g.
       G      Apply the following `s' modifier once to each word in the event line.

SHELL BUILTIN COMMANDS

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

        .  filename [arguments]
       source filename [arguments]
              Read and execute commands from filename in the current shell environment and return
              the  exit  status of the last command executed from filename.  If filename does not
              contain a slash, file names in PATH are  used  to  find  the  directory  containing
              filename.   The file searched for in PATH need not be executable.  When bash is not
              in posix mode, the current directory is searched if no file is found in  PATH.   If
              the  sourcepath  option to the shopt builtin command is turned off, the PATH is not
              searched.  If any arguments are supplied, they  become  the  positional  parameters
              when filename is executed.  Otherwise the positional parameters are unchanged.  The
              return status is the status of the last command exited within the script (0  if  no
              commands are executed), and false if filename is not found or cannot be read.

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

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

       bind [-m keymap] [-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-standard,  emacs-meta,  emacs-ctlx,
                     vi,  vi-move,  vi-command,  and  vi-insert.  vi is equivalent to vi-command;
                     emacs is equivalent to emacs-standard.
              -l     List the names of all readline functions.
              -p     Display readline function names and bindings in such a way that they can  be
                     re-read.
              -P     List current readline function names and bindings.
              -s     Display  readline  key sequences bound to macros and the strings they output
                     in such a way that they can be re-read.
              -S     Display readline key sequences bound to macros and the strings they output.
              -v     Display readline variable names and values in such a way that  they  can  be
                     re-read.
              -V     List current readline variable names and values.
              -f filename
                     Read key bindings from filename.
              -q function
                     Query about which keys invoke the named function.
              -u function
                     Unbind all keys bound to the named function.
              -r keyseq
                     Remove any current binding for keyseq.
              -x keyseq:shell-command
                     Cause  shell-command  to  be  executed  whenever  keyseq  is  entered.  When
                     shell-command is executed, the shell sets the READLINE_LINE variable to  the
                     contents  of the readline line buffer and the READLINE_POINT variable to the
                     current location of the insertion point.  If the  executed  command  changes
                     the  value  of  READLINE_LINE  or  READLINE_POINT,  those new values will be
                     reflected in the editing state.

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

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

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

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

       cd [-L|[-P [-e]]] [dir]
              Change  the  current  directory to dir.  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
              followed.  If the -e option is supplied with -P, and the current working  directory
              cannot  be  successfully  determined  after  a successful directory change, cd will
              return an unsuccessful status.  An argument of - is equivalent to  $OLDPWD.   If  a
              non-empty  directory  name  from CDPATH is used, or if - is the first argument, and
              the directory change is successful,  the  absolute  pathname  of  the  new  working
              directory  is  written  to  the  standard  output.  The return value is true if the
              directory was successfully changed; false otherwise.

       command [-pVv] command [arg ...]
              Run command with args suppressing the normal shell function  lookup.  Only  builtin
              commands  or  commands  found in the PATH are executed.  If the -p option is given,
              the search for command is  performed  using  a  default  value  for  PATH  that  is
              guaranteed to find all of the standard utilities.  If either the -V or -v option is
              supplied, a description of command is printed.  The -v option causes a single  word
              indicating  the command or 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 cannot be found, the exit status is  127.
              Otherwise, the exit status of the command builtin is the exit status of command.

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

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

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

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

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

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

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

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

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

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

       declare [-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 definitions; only the
              function name and attributes are printed.  If the extdebug shell option is  enabled
              using shopt, the source file name and line number where the function is defined are
              displayed as well.  The -F option implies -f.  The -g option forces variables to be
              created  or  modified at the global scope, even when declare is executed in a shell
              function.  It is ignored in all other cases.  The following options can be used  to
              restrict  output  to  variables  with  the specified attribute or to give variables
              attributes:
              -a     Each name is an indexed array variable (see Arrays above).
              -A     Each name is an associative array variable (see Arrays above).
              -f     Use function names only.
              -i     The variable is treated as an integer; arithmetic evaluation (see ARITHMETIC
                     EVALUATION above) is performed when the variable is assigned a value.
              -l     When  the  variable  is  assigned  a  value,  all  upper-case characters are
                     converted to lower-case.  The upper-case attribute is disabled.
              -r     Make names  readonly.   These  names  cannot  then  be  assigned  values  by
                     subsequent assignment statements or unset.
              -t     Give  each name the trace attribute.  Traced functions inherit the DEBUG and
                     RETURN traps from the calling shell.  The trace  attribute  has  no  special
                     meaning for variables.
              -u     When  the  variable  is  assigned  a  value,  all  lower-case characters are
                     converted to upper-case.  The lower-case attribute is disabled.
              -x     Mark names for export to subsequent commands via the environment.

              Using `+' instead of `-' turns off the attribute instead, with the exceptions  that
              +a may not be used to destroy an array variable and +r will not remove the readonly
              attribute.  When used in a function, 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, prefixing 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 table, 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  jobspec  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,  interpretation of the following backslash-escaped characters is
              enabled.  The -E option disables the interpretation  of  these  escape  characters,
              even  on  systems where they are interpreted by default.  The xpg_echo shell option
              may be used to dynamically determine whether  or  not  echo  expands  these  escape
              characters  by  default.   echo  does  not interpret -- to mean the end of options.
              echo interprets the following escape sequences:
              \a     alert (bell)
              \b     backspace
              \c     suppress further output
              \e
              \E     an escape character
              \f     form feed
              \n     new line
              \r     carriage return
              \t     horizontal tab
              \v     vertical tab
              \\     backslash
              \0nnn  the eight-bit character whose value is the octal value nnn  (zero  to  three
                     octal digits)
              \xHH   the  eight-bit character whose value is the hexadecimal value HH (one or two
                     hex digits)
              \uHHHH the Unicode (ISO/IEC 10646) character whose value is the  hexadecimal  value
                     HHHH (one to four hex digits)
              \UHHHHHHHH
                     the  Unicode  (ISO/IEC 10646) character whose value is the hexadecimal value
                     HHHHHHHH (one to eight hex digits)

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

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

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

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

       export [-fn] [name[=word]] ...
       export -p
              The  supplied  names  are  marked  for  automatic  export  to  the  environment  of
              subsequently  executed  commands.   If  the  -f option is given, the names refer to
              functions.  If no names are given, or if the -p option is supplied, a list  of  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 function.

       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  current  command
              number).  If last is not specified it is set to the current command for listing (so
              that ``fc -l -10'' prints the last 10 commands) and to first otherwise.   If  first
              is not specified it is set to the previous command for editing and -16 for listing.

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

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

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

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

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

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

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

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

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

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

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

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

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

              The return status is 0 unless no command matches pattern.

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

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

       jobs [-lnprs] [ jobspec ... ]
       jobs -x command [ args ... ]
              The first form lists the active jobs.  The options have the following meanings:
              -l     List process IDs in addition to the normal information.
              -n     Display  information only about jobs that have changed status since the user
                     was last notified of their status.
              -p     List only the process ID of the job's process group leader.
              -r     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 ARITHMETIC EVALUATION
              above).  If the last arg evaluates to 0, let returns 1; 0 is returned otherwise.

       local [option] [name[=value] ...]
              For each argument, a local variable named name is created, and assigned value.  The
              option  can be any of the options accepted by declare.  When local is used within a
              function, it causes the variable name to have a visible scope  restricted  to  that
              function  and  its  children.   With  no  operands,  local  writes  a list of local
              variables to the standard output.  It is an error to use local when  not  within  a
              function.   The  return  status  is  0  unless local is used outside a function, an
              invalid name is supplied, or name is a readonly variable.

       logout Exit a login shell.

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

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

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

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

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

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

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

              The  format  is  a  character  string  which contains three types of objects: plain
              characters, which are simply copied to standard output, character escape sequences,
              which  are  converted and copied to the standard output, and format specifications,
              each of which causes printing of the next successive argument.  In addition to  the
              standard   printf(1)   format   specifications,  printf  interprets  the  following
              extensions:
              %b     causes printf to expand backslash  escape  sequences  in  the  corresponding
                     argument  (except  that  \c terminates output, backslashes in \', \", and \?
                     are not removed, and octal escapes beginning with \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 constants, except that a
              leading  plus or minus sign is allowed, and if the leading character is a single or
              double quote, the value is the ASCII value of the following character.

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

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

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

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

       read [-ers] [-a aname] [-d delim] [-i text]  [-n  nchars]  [-N  nchars]  [-p  prompt]  [-t
       timeout] [-u fd] [name ...]
              One  line  is read from the standard input, or from the file descriptor fd supplied
              as an argument to the -u option, and the first word is assigned to the first  name,
              the  second  word  to  the  second  name,  and so on, with leftover words and their
              intervening separators assigned to the last name.  If there are  fewer  words  read
              from  the  input  stream than names, the remaining names are assigned empty values.
              The characters in IFS are used  to  split  the  line  into  words.   The  backslash
              character (\) may be used to remove any special meaning for the next character read
              and for line continuation.  Options, if supplied, have the following meanings:
              -a aname
                     The words are assigned to sequential indices of the  array  variable  aname,
                     starting  at  0.   aname is unset before any new values are assigned.  Other
                     name arguments are ignored.
              -d delim
                     The first character of delim is used to terminate  the  input  line,  rather
                     than newline.
              -e     If  the  standard  input  is  coming from a terminal, readline (see READLINE
                     above) is used to obtain the line.  Readline uses the current  (or  default,
                     if line editing was not previously active) editing settings.
              -i text
                     If  readline is being used to read the line, text is placed into the editing
                     buffer before editing begins.
              -n nchars
                     read returns after reading nchars  characters  rather  than  waiting  for  a
                     complete  line  of  input,  but  honor  a  delimiter  if  fewer  than nchars
                     characters are read before the delimiter.
              -N nchars
                     read returns after reading exactly nchars characters rather than waiting for
                     a  complete  line  of  input,  unless  EOF is encountered or read times out.
                     Delimiter characters encountered in the input are not treated specially  and
                     do not cause read to return until nchars characters are read.
              -p prompt
                     Display  prompt  on  standard  error,  without  a  trailing  newline, before
                     attempting to read any input.  The prompt is  displayed  only  if  input  is
                     coming from a terminal.
              -r     Backslash  does not act as an escape character.  The backslash is considered
                     to be part of the line.  In particular, a backslash-newline pair may not  be
                     used as a line continuation.
              -s     Silent mode.  If input is coming from a terminal, characters are not echoed.
              -t timeout
                     Cause read to time out and return failure if a complete line of input is not
                     read within timeout seconds.   timeout  may  be  a  decimal  number  with  a
                     fractional  portion  following  the  decimal  point.   This  option  is only
                     effective if read is reading input from a terminal, pipe, or  other  special
                     file;  it  has  no effect when reading from regular files.  If 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  variable  REPLY.   The
              return  code  is  zero, unless end-of-file is encountered, read times out (in which
              case the return code is greater  than  128),  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  cannot  be  reset.   In  posix  mode, only shell
              variables are listed.  The output is sorted according to the current locale.   When
              options are specified, they set or unset shell attributes.  Any arguments remaining
              after option processing are treated as values for the positional parameters and are
              assigned,  in order, to $1, $2, ...  $n.  Options, if specified, have the following
              meanings:
              -a      Automatically mark variables and functions which are  modified  or  created
                      for export to the environment of subsequent commands.
              -b      Report  the  status  of terminated background jobs immediately, rather than
                      before the next primary prompt.  This is effective only when job control is
                      enabled.
              -e      Exit  immediately  if  a  pipeline  (which  may  consist of a single simple
                      command),  a 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 environment 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  processes run in a separate process group and a line containing
                      their exit status is printed upon their completion.
              -n      Read commands but do not execute them.  This may be used to check  a  shell
                      script for syntax errors.  This is ignored by interactive shells.
              -o option-name
                      The option-name can be one of the following:
                      allexport
                              Same as -a.
                      braceexpand
                              Same as -B.
                      emacs   Use an emacs-style command line editing interface.  This is enabled
                              by default when the shell  is  interactive,  unless  the  shell  is
                              started with the --noediting option.  This also affects the editing
                              interface used for read -e.
                      errexit Same as -e.
                      errtrace
                              Same as -E.
                      functrace
                              Same as -T.
                      hashall Same as -h.
                      histexpand
                              Same as -H.
                      history Enable command history, as described  above  under  HISTORY.   This
                              option is on by default in interactive shells.
                      ignoreeof
                              The  effect  is  as  if the shell command ``IGNOREEOF=10'' had been
                              executed (see Shell Variables above).
                      keyword Same as -k.
                      monitor Same as -m.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Currently ignored.
                      notify  Same as -b.
                      nounset Same as -u.
                      onecmd  Same as -t.
                      physical
                              Same as -P.
                      pipefail
                              If set, the return value of a pipeline is the  value  of  the  last
                              (rightmost)  command to exit with a non-zero status, or zero if all
                              commands  in  the  pipeline  exit  successfully.   This  option  is
                              disabled by default.
                      posix   Change  the  behavior  of  bash where the default operation differs
                              from the POSIX standard to match the standard (posix mode).
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      vi      Use a vi-style command line editing interface.  This  also  affects
                              the editing interface used for read -e.
                      xtrace  Same as -x.
                      If  -o  is  supplied with no option-name, the values of the current options
                      are printed.  If +o is supplied  with  no  option-name,  a  series  of  set
                      commands  to  recreate  the  current  option  settings  is displayed on the
                      standard output.
              -p      Turn on privileged mode.  In this mode, the $ENV and  $BASH_ENV  files  are
                      not  processed, shell functions are not inherited from the environment, and
                      the SHELLOPTS, BASHOPTS, CDPATH, and GLOBIGNORE variables, if  they  appear
                      in  the  environment,  are  ignored.   If  the  shell  is  started with the
                      effective user (group) id not equal to the real user (group) id, and the -p
                      option  is  not supplied, these actions are taken and the effective user id
                      is set to the real user id.  If the -p option is supplied at  startup,  the
                      effective  user  id  is  not  reset.   Turning  this  option off causes the
                      effective user and group ids to be set to the real user and group ids.
              -t      Exit after reading and executing one command.
              -u      Treat unset variables and parameters other than the special parameters  "@"
                      and  "*"  as an error when performing parameter expansion.  If expansion is
                      attempted on an unset variable or parameter,  the  shell  prints  an  error
                      message, and, if not interactive, exits with a non-zero status.
              -v      Print shell input lines as they are read.
              -x      After  expanding  each  simple  command,  for command, case command, select
                      command, or arithmetic for command, display  the  expanded  value  of  PS4,
                      followed by the command and its expanded arguments or associated word list.
              -B      The shell performs brace expansion (see Brace Expansion above).  This is on
                      by default.
              -C      If set, bash does not overwrite an existing file with the  >,  >&,  and  <>
                      redirection  operators.   This may be overridden when creating output files
                      by using the redirection operator >| instead of >.
              -E      If  set,  any  trap  on  ERR  is  inherited  by  shell  functions,  command
                      substitutions,  and  commands  executed in a subshell environment.  The ERR
                      trap is normally not inherited in such cases.
              -H      Enable !  style history substitution.  This option is on  by  default  when
                      the shell is interactive.
              -P      If  set,  the  shell does not 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 parameters are set to the args, even if
                      some of them begin with a -.
              -       Signal the end of options, cause all remaining args to be assigned  to  the
                      positional parameters.  The -x and -v options are turned off.  If there are
                      no args, the positional parameters remain unchanged.

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

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

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

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

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

              The list of shopt options is:

              autocd  If set, a command name that is the name of a directory is executed as if it
                      were  the  argument  to  the  cd  command.   This  option  is  only used by
                      interactive shells.
              cdable_vars
                      If set, an argument to the cd builtin command that is not  a  directory  is
                      assumed to be the name of a variable whose value is the directory to change
                      to.
              cdspell If set, minor errors in the spelling of  a  directory  component  in  a  cd
                      command   will  be  corrected.   The  errors  checked  for  are  transposed
                      characters, a  missing  character,  and  one  character  too  many.   If  a
                      correction  is  found,  the corrected file name is printed, and the command
                      proceeds.  This option is only used by interactive shells.
              checkhash
                      If set, bash checks that a command found in the hash  table  exists  before
                      trying  to execute it.  If a hashed command no longer exists, a normal path
                      search is performed.
              checkjobs
                      If set, bash lists the status  of  any  stopped  and  running  jobs  before
                      exiting  an  interactive  shell.   If any jobs are running, this causes the
                      exit to be deferred until a second exit is attempted without an intervening
                      command (see JOB CONTROL above).  The shell always postpones exiting if any
                      jobs are stopped.
              checkwinsize
                      If set, bash checks the window size after each command and,  if  necessary,
                      updates the values of LINES and COLUMNS.
              cmdhist If  set,  bash attempts to save all lines of a multiple-line command in the
                      same history entry.  This allows easy re-editing of multi-line commands.
              compat31
                      If set, bash changes its behavior to that of version 3.1  with  respect  to
                      quoted arguments to the [[ conditional command's =~ operator.
              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  number)  and  the  characters  between  the  single  quotes  are
                      considered quoted.  This is the behavior of posix mode through version 4.1.
                      The default bash behavior remains as in previous versions.
              dirspell
                      If set, bash attempts spelling correction on directory  names  during  word
                      completion if the directory name initially supplied does not exist.
              dotglob If  set,  bash  includes  filenames  beginning with a `.' in the results of
                      pathname expansion.
              execfail
                      If set, a non-interactive shell will not exit if it cannot execute the file
                      specified as an argument to the exec builtin command.  An interactive shell
                      does not exit if exec fails.
              expand_aliases
                      If set, aliases are expanded as described above under ALIASES.  This option
                      is enabled by default for interactive shells.
              extdebug
                      If set, behavior intended for use by debuggers is enabled:
                      1.     The  -F  option to the declare builtin displays the source file name
                             and line number corresponding to each function name supplied  as  an
                             argument.
                      2.     If  the  command run by the DEBUG trap returns a non-zero value, the
                             next command is skipped and not executed.
                      3.     If the command run by the DEBUG trap returns a value of 2,  and  the
                             shell  is  executing  in  a  subroutine (a shell function or a shell
                             script executed by the . or source builtins), a call  to  return  is
                             simulated.
                      4.     BASH_ARGC   and   BASH_ARGV   are  updated  as  described  in  their
                             descriptions above.
                      5.     Function tracing is enabled:  command substitution, shell functions,
                             and  subshells invoked with ( command ) inherit the DEBUG and RETURN
                             traps.
                      6.     Error tracing is enabled:  command  substitution,  shell  functions,
                             and subshells invoked with ( command ) inherit the ERR trap.
              extglob If  set,  the  extended  pattern  matching  features  described above under
                      Pathname Expansion are enabled.
              extquote
                      If set, $'string' and $"string" quoting is  performed  within  ${parameter}
                      expansions enclosed in double quotes.  This option is enabled by default.
              failglob
                      If  set,  patterns  which fail to match filenames during pathname expansion
                      result in an expansion error.
              force_fignore
                      If set, the suffixes specified by the FIGNORE shell variable cause words to
                      be  ignored  when  performing word completion even if the ignored words are
                      the only possible completions.  See SHELL VARIABLES above for a description
                      of FIGNORE.  This option is enabled by default.
              globstar
                      If  set, the pattern ** used in a pathname expansion context will match all
                      files and zero or more directories and subdirectories.  If the  pattern  is
                      followed by a /, only directories and subdirectories match.
              gnu_errfmt
                      If  set, shell error messages are written in the standard GNU error message
                      format.
              histappend
                      If set, the history list is appended to the file named by the value of  the
                      HISTFILE variable when the shell exits, rather than overwriting the file.
              histreedit
                      If  set, and readline is being used, a user is given the opportunity to re-
                      edit a failed history substitution.
              histverify
                      If set, and readline is being used, the results of history substitution are
                      not immediately passed to the shell parser.  Instead, the resulting line is
                      loaded into the readline editing buffer, allowing further modification.
              hostcomplete
                      If set, and readline is being used, bash will attempt to  perform  hostname
                      completion  when  a  word containing a @ is being completed (see Completing
                      under READLINE above).  This is enabled by default.
              huponexit
                      If set, bash will send SIGHUP to all jobs when an interactive  login  shell
                      exits.
              interactive_comments
                      If  set, allow a word beginning with # to cause that word and all remaining
                      characters on that line to be ignored in an interactive shell (see COMMENTS
                      above).  This option is enabled by default.
              lastpipe
                      If set, and job control is not active, the shell runs the last command of a
                      pipeline not executed in the background in the current shell environment.
              lithist If set, and the cmdhist option is enabled, multi-line commands are saved to
                      the  history  with embedded newlines rather than using semicolon separators
                      where possible.
              login_shell
                      The shell sets this  option  if  it  is  started  as  a  login  shell  (see
                      INVOCATION above).  The value may not be changed.
              mailwarn
                      If  set,  and a file that bash is checking for mail has been accessed since
                      the last time it was checked, the message ``The mail in mailfile  has  been
                      read'' is displayed.
              no_empty_cmd_completion
                      If  set,  and  readline  is being used, bash will not attempt to search the
                      PATH for possible completions when completion  is  attempted  on  an  empty
                      line.
              nocaseglob
                      If   set,  bash  matches  filenames  in  a  case-insensitive  fashion  when
                      performing pathname expansion (see Pathname Expansion above).
              nocasematch
                      If set, bash matches patterns in a case-insensitive fashion when performing
                      matching while executing case or [[ conditional commands.
              nullglob
                      If  set,  bash allows patterns which match no files (see Pathname Expansion
                      above) to expand to a null string, rather than themselves.
              progcomp
                      If set, the programmable completion facilities (see Programmable Completion
                      above) are enabled.  This option is enabled by default.
              promptvars
                      If  set,  prompt strings undergo parameter expansion, command substitution,
                      arithmetic expansion, and quote removal after being expanded  as  described
                      in PROMPTING above.  This option is enabled by default.
              restricted_shell
                      The  shell  sets  this  option  if  it  is  started in restricted mode (see
                      RESTRICTED SHELL below).  The value may not be changed.  This is not  reset
                      when the startup files are executed, allowing the startup files to discover
                      whether or not a shell is restricted.
              shift_verbose
                      If set, the shift builtin prints an error  message  when  the  shift  count
                      exceeds the number of positional parameters.
              sourcepath
                      If set, the source (.) builtin uses the value of PATH to find the directory
                      containing the file supplied as an argument.  This  option  is  enabled  by
                      default.
              xpg_echo
                      If set, the echo builtin expands backslash-escape sequences by default.

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

       test expr
       [ expr ]
              Return a status of 0 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 precedence is used when there are five or more arguments.
              ! expr True if expr is false.
              ( expr )
                     Returns the value of  expr.   This  may  be  used  to  override  the  normal
                     precedence of operators.
              expr1 -a expr2
                     True if both expr1 and expr2 are true.
              expr1 -o expr2
                     True if either expr1 or expr2 is true.

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

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

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

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

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

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

              If  a  sigspec  is ERR, the command arg is executed whenever a simple 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  or  reset.   Trapped
              signals that are not being ignored are reset to their original values in a subshell
              or subshell environment when one is created.  The return status  is  false  if  any
              sigspec is invalid; otherwise trap returns true.

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

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

              If  limit is given, 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.

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

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

       unset [-fv] [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
              function, and the function definition is removed.  Each unset variable or  function
              is  removed  from  the  environment  passed  to  subsequent  commands.   If  any of
              COMP_WORDBREAKS, RANDOM, SECONDS, LINENO, HISTCMD, FUNCNAME,  GROUPS,  or  DIRSTACK
              are unset, they lose their special properties, even if they are subsequently reset.
              The exit status is true unless a name is readonly.

       wait [n ...]
              Wait for each specified process and return its termination status.  Each n may be a
              process  ID  or  a job specification; if a job spec is given, all processes in that
              job's pipeline are waited for.  If n is  not  given,  all  currently  active  child
              processes  are  waited  for,  and the return status is zero.  If n specifies a non-
              existent process or job, the return status is 127.  Otherwise, the return status is
              the exit status of the last process or job waited for.

RESTRICTED SHELL

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

       ·      changing directories with cd

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

       ·      specifying command names containing /

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

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

       ·      importing function definitions from the shell environment at startup

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

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

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

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

       ·      using the enable builtin command to enable disabled shell builtins

       ·      specifying the -p option to the command builtin command

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

       These restrictions are enforced after any startup files are read.

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

SEE ALSO

       Bash Reference Manual, Brian Fox and Chet Ramey
       The Gnu Readline Library, Brian Fox and Chet Ramey
       The Gnu History Library, Brian Fox and Chet Ramey
       Portable Operating System Interface (POSIX) Part 2: Shell and Utilities, IEEE
       sh(1), ksh(1), csh(1)
       emacs(1), vi(1)
       readline(3)

FILES

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

AUTHORS

       Brian Fox, Free Software Foundation
       bfox@gnu.org

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

BUG REPORTS

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

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

       ALL bug reports should include:

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

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

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

BUGS

       It's too big and too slow.

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

       Aliases are confusing in some uses.

       Shell builtin commands and functions are not stoppable/restartable.

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

       Array variables may not (yet) be exported.

       There may be only one active coprocess at a time.