     BASH(1)                        GNU Bash 4.3                         BASH(1)
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     NAME
          bash - GNU Bourne-Again SHell

     SYNOPSIS
          bash [options] [command_string | file]

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

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

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

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

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

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          --        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 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 personal initialization file
               ~/.bashrc if the shell is interactive.  This option is on by
               default if the shell is invoked as sh.

          --posix
               Change the behavior of bash where the default operation differs
               from the POSIX standard to match the standard (posix mode).  See
               SEE ALSO below for a reference to a document that details how
               posix mode affects bash's behavior.

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

          --verbose
               Equivalent to  -v.

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

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

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

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

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

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

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

          When an interactive shell that is not a login shell is started, bash
          reads and executes commands from ~/.bashrc, if that file exists.  This

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          may be inhibited by using the --norc option.  The --rcfile file option
          will force bash to read and execute commands from file instead of
          ~/.bashrc.

          When bash is started non-interactively, to run a shell script, for
          example, it looks for the variable BASH_ENV in the environment,
          expands its value if it appears there, and uses the expanded value as
          the name of a file to read and execute.  Bash behaves as if the
          following command were executed:

               if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
          but the value of the PATH variable is not used to search for the
          filename.

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

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

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

          If the shell is started with the effective user (group) id not equal
          to the real user (group) id, and the -p option is not supplied, no
          startup files are read, shell functions are not inherited from the
          environment, the SHELLOPTS, BASHOPTS, CDPATH, and GLOBIGNORE
          variables, if they appear in the environment, are ignored, and the

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          effective user id is set to the real user id.  If the -p option is
          supplied at invocation, the startup behavior is the same, but the
          effective user id is not reset.

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

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

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

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

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

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

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

          The standard output of command is connected via a pipe to the standard
          input of command2.  This connection is performed before any

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

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

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

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

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

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

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

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

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

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

               command1 && command2

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

          An OR list has the form

               command1 || command2

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

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

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

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

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

          [[ expression ]]
               Return a status of 0 or 1 depending on the evaluation of the
               conditional expression expression.  Expressions are composed of
               the primaries described below under CONDITIONAL EXPRESSIONS.
               Word splitting and pathname expansion are not performed on the

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               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.

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

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

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

               ( expression )
                    Returns the value of expression.  This may be used to
                    override the normal precedence of operators.
               ! expression
                    True if expression is false.

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               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

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               substitution and quote removal.  Each pattern examined is
               expanded using tilde expansion, parameter and variable expansion,
               arithmetic substitution, command substitution, and process
               substitution.  If the shell option nocasematch is enabled, the
               match is performed without regard to the case of alphabetic
               characters.  When a match is found, the corresponding list is
               executed.  If the ;; operator is used, no subsequent matches are
               attempted after the first pattern match.  Using ;& in place of ;;
               causes execution to continue with the list associated with the
               next set of patterns.  Using ;;& in place of ;; causes the shell
               to test the next pattern list in the statement, if any, and
               execute any associated list on a successful match.  The exit
               status is zero if no pattern matches.  Otherwise, it is the exit
               status of the last command executed in list.

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

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

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

          The format for a coprocess is:

               coproc [NAME] command [redirections]

          This creates a coprocess named NAME.  If NAME is not supplied, the
          default name is COPROC.  NAME must not be supplied if command is a
          simple command (see above); otherwise, it is interpreted as the first
          word of the simple command.  When the coprocess is executed, the shell
          creates an array variable (see Arrays below) named NAME in the context
          of the executing shell.  The standard output of command is connected
          via a pipe to a file descriptor in the executing shell, and that file

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          descriptor is assigned to NAME[0].  The standard input of command is
          connected via a pipe to a file descriptor in the executing shell, and
          that file descriptor is assigned to NAME[1].  This pipe is established
          before any redirections specified by the command (see REDIRECTION
          below).  The file descriptors can be utilized as arguments to shell
          commands and redirections using standard word expansions.  The file
          descriptors are not available in subshells.  The process ID of the
          shell spawned to execute the coprocess is available as the value of
          the variable NAME_PID.  The wait builtin command may be used to wait
          for the coprocess to terminate.

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

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

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

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

     QUOTING
          Quoting is used to remove the special meaning of certain characters or
          words to the shell.  Quoting can be used to disable special treatment
          for special characters, to prevent reserved words from being

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          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

                                       - 12 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               \    single quote
               \    double quote
               \nnn the eight-bit character whose value is the octal value nnn
                    (one to three digits)
               \xHH the eight-bit character whose value is the hexadecimal value
                    HH (one or two hex digits)
               \uHHHH
                    the Unicode (ISO/IEC 10646) character whose value is the
                    hexadecimal value HHHH (one to four hex digits)
               \UHHHHHHHH
                    the Unicode (ISO/IEC 10646) character whose value is the
                    hexadecimal value HHHHHHHH (one to eight hex digits)
               \cx  a control-x character
          The expanded result is single-quoted, as if the dollar sign had not
          been present.

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

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

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

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

               name=[value]

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

                                       - 13 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

          A variable can be assigned the nameref attribute using the -n option
          to the declare or local builtin commands (see the descriptions of
          declare and local below) to create a nameref, or a reference to
          another variable.  This allows variables to be manipulated indirectly.
          Whenever the nameref variable is referenced or assigned to, the
          operation is actually performed on the variable specified by the
          nameref variable's value.  A nameref is commonly used within shell
          functions to refer to a variable whose name is passed as an argument
          to the function.  For instance, if a variable name is passed to a
          shell function as its first argument, running

               declare -n ref=$1
          inside the function creates a nameref variable ref whose value is the
          variable name passed as the first argument.  References and
          assignments to ref are treated as references and assignments to the
          variable whose name was passed as $1.  If the control variable in a
          for loop has the nameref attribute, the list of words can be a list of
          shell variables, and a name reference will be established for each
          word in the list, in turn, when the loop is executed.  Array variables
          cannot be given the -n attribute.  However, nameref variables can
          reference array variables and subscripted array variables.  Namerefs
          can be unset using the -n option to the unset builtin.  Otherwise, if
          unset is executed with the name of a nameref variable as an argument,
          the variable referenced by the nameref variable will be unset.

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

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

                                       - 14 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

                                       - 15 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

        Shell Variables
          The following variables are set by the shell:

          BASH Expands to the full filename used to invoke this instance of
               bash.
          BASHOPTS
               A colon-separated list of enabled shell options.  Each word in
               the list is a valid argument for the -s option to the shopt
               builtin command (see SHELL BUILTIN COMMANDS below).  The options
               appearing in BASHOPTS are those reported as on by shopt.  If this
               variable is in the environment when bash starts up, each shell
               option in the list will be enabled before reading any startup
               files.  This variable is read-only.
          BASHPID
               Expands to the process ID of the current bash process.  This
               differs from $$ under certain circumstances, such as subshells
               that do not require bash to be re-initialized.
          BASH_ALIASES
               An associative array variable whose members correspond to the
               internal list of aliases as maintained by the alias builtin.
               Elements added to this array appear in the alias list; unsetting
               array elements cause aliases to be removed from the alias list.
          BASH_ARGC
               An array variable whose values are the number of parameters in
               each frame of the current bash execution call stack.  The number
               of parameters to the current subroutine (shell function or script
               executed with . or source) is at the top of the stack.  When a
               subroutine is executed, the number of parameters passed is pushed
               onto BASH_ARGC.  The shell sets BASH_ARGC only when in extended
               debugging mode (see the description of the extdebug option to the
               shopt builtin below)
          BASH_ARGV
               An array variable containing all of the parameters in the current
               bash execution call stack.  The final parameter of the last
               subroutine call is at the top of the stack; the first parameter
               of the initial call is at the bottom.  When a subroutine is
               executed, the parameters supplied are pushed onto BASH_ARGV.  The
               shell sets BASH_ARGV only when in extended debugging mode (see
               the description of the extdebug option to the shopt builtin
               below)
          BASH_CMDS
               An associative array variable whose members correspond to the
               internal hash table of commands as maintained by the hash
               builtin.  Elements added to this array appear in the hash table;
               unsetting array elements cause commands to be removed from the
               hash table.
          BASH_COMMAND
               The command currently being executed or about to be executed,
               unless the shell is executing a command as the result of a trap,
               in which case it is the command executing at the time of the
               trap.

                                       - 16 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          BASH_EXECUTION_STRING
               The command argument to the -c invocation option.
          BASH_LINENO
               An array variable whose members are the line numbers in source
               files where each corresponding member of FUNCNAME was invoked.
               ${BASH_LINENO[$i]} is the line number in the source file
               (${BASH_SOURCE[$i+1]}) where ${FUNCNAME[$i]} was called (or
               ${BASH_LINENO[$i-1]} if referenced within another shell
               function).  Use LINENO to obtain the current line number.
          BASH_REMATCH
               An array variable whose members are assigned by the =~ binary
               operator to the [[ conditional command.  The element with index 0
               is the portion of the string matching the entire regular
               expression.  The element with index n is the portion of the
               string matching the nth parenthesized subexpression.  This
               variable is read-only.
          BASH_SOURCE
               An array variable whose members are the source filenames where
               the corresponding shell function names in the FUNCNAME array
               variable are defined.  The shell function ${FUNCNAME[$i]} is
               defined in the file ${BASH_SOURCE[$i]} and called from
               ${BASH_SOURCE[$i+1]}.
          BASH_SUBSHELL
               Incremented by one within each subshell or subshell environment
               when the shell begins executing in that environment.  The initial
               value is 0.
          BASH_VERSINFO
               A readonly array variable whose members hold version information
               for this instance of bash.  The values assigned to the array
               members are as follows:

               BASH_VERSINFO[0]        The major version number (the release).
               BASH_VERSINFO[1]        The minor version number (the version).
               BASH_VERSINFO[2]        The patch level.
               BASH_VERSINFO[3]        The build version.
               BASH_VERSINFO[4]        The release status (e.g., beta1).
               BASH_VERSINFO[5]        The value of MACHTYPE.
          BASH_VERSION
               Expands to a string describing the version of this instance of
               bash.
          COMP_CWORD
               An index into ${COMP_WORDS} of the word containing the current
               cursor position.  This variable is available only in shell
               functions invoked by the programmable completion facilities (see
               Programmable Completion below).
          COMP_KEY
               The key (or final key of a key sequence) used to invoke the
               current completion function.
          COMP_LINE
               The current command line.  This variable is available only in
               shell functions and external commands invoked by the programmable

                                       - 17 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               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.

                                       - 18 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               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.

                                       - 19 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          PIPESTATUS
               An array variable (see Arrays below) containing a list of exit
               status values from the processes in the most-recently-executed
               foreground pipeline (which may contain only a single command).
          PPID The process ID of the shell's parent.  This variable is readonly.
          PWD  The current working directory as set by the cd command.
          RANDOM
               Each time this parameter is referenced, a random integer between
               0 and 32767 is generated.  The sequence of random numbers may be
               initialized by assigning a value to RANDOM.  If RANDOM is unset,
               it loses its special properties, even if it is subsequently
               reset.
          READLINE_LINE
               The contents of the readline line buffer, for use with "bind -x"
               (see SHELL BUILTIN COMMANDS below).
          READLINE_POINT
               The position of the insertion point in the readline line buffer,
               for use with "bind -x" (see SHELL BUILTIN COMMANDS below).
          REPLY
               Set to the line of input read by the read builtin command when no
               arguments are supplied.
          SECONDS
               Each time this parameter is referenced, the number of seconds
               since shell invocation is returned.  If a value is assigned to
               SECONDS, the value returned upon subsequent references is the
               number of seconds since the assignment plus the value assigned.
               If SECONDS is unset, it loses its special properties, even if it
               is subsequently reset.
          SHELLOPTS
               A colon-separated list of enabled shell options.  Each word in
               the list is a valid argument for the -o option to the set builtin
               command (see SHELL BUILTIN COMMANDS below).  The options
               appearing in SHELLOPTS are those reported as on by set -o.  If
               this variable is in the environment when bash starts up, each
               shell option in the list will be enabled before reading any
               startup files.  This variable is read-only.
          SHLVL
               Incremented by one each time an instance of bash is started.
          UID  Expands to the user ID of the current user, initialized at shell
               startup.  This variable is readonly.

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

          BASH_COMPAT
               The value is used to set the shell's compatibility level.  See
               the description of the shopt builtin below under SHELL BUILTIN
               COMMANDS for a description of the various compatibility levels
               and their effects.  The value may be a decimal number (e.g., 4.2)
               or an integer (e.g., 42) corresponding to the desired
               compatibility level.  If BASH_COMPAT is unset or set to the empty

                                       - 20 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               string, the compatibility level is set to the default for the
               current version.  If BASH_COMPAT is set to a value that is not
               one of the valid compatibility levels, the shell prints an error
               message and sets the compatibility level to the default for the
               current version.  The valid compatibility levels correspond to
               the compatibility options accepted by the shopt builtin described
               below (for example, compat42 means that 4.2 and 42 are valid
               values).  The current version is also a valid value.
          BASH_ENV
               If this parameter is set when bash is executing a shell script,
               its value is interpreted as a filename containing commands to
               initialize the shell, as in ~/.bashrc.  The value of BASH_ENV is
               subjected to parameter expansion, command substitution, and
               arithmetic expansion before being interpreted as a filename.
               PATH is not used to search for the resultant filename.
          BASH_XTRACEFD
               If set to an integer corresponding to a valid file descriptor,
               bash will write the trace output generated when set -x is enabled
               to that file descriptor.  The file descriptor is closed when
               BASH_XTRACEFD is unset or assigned a new value.  Unsetting
               BASH_XTRACEFD or assigning it the empty string causes the trace
               output to be sent to the standard error.  Note that setting
               BASH_XTRACEFD to 2 (the standard error file descriptor) and then
               unsetting it will result in the standard error being closed.
          CDPATH
               The search path for the cd command.  This is a colon-separated
               list of directories in which the shell looks for destination
               directories specified by the cd command.  A sample value is
               ".:~:/usr".
          CHILD_MAX
               Set the number of exited child status values for the shell to
               remember.  Bash will not allow this value to be decreased below a
               POSIX-mandated minimum, and there is a maximum value (currently
               8192) that this may not exceed.  The minimum value is system-
               dependent.
          COLUMNS
               Used by the select compound command to determine the terminal
               width when printing selection lists.  Automatically set if the
               checkwinsize option is enabled or in an interactive shell upon
               receipt of a SIGWINCH.
          COMPREPLY
               An array variable from which bash reads the possible completions
               generated by a shell function invoked by the programmable
               completion facility (see Programmable Completion below).  Each
               array element contains one possible completion.
          EMACS
               If bash finds this variable in the environment when the shell
               starts with value "t", it assumes that the shell is running in an
               Emacs shell buffer and disables line editing.
          ENV  Similar to BASH_ENV; used when the shell is invoked in POSIX
               mode.

                                       - 21 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          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:~".
          FUNCNEST
               If set to a numeric value greater than 0, defines a maximum
               function nesting level.  Function invocations that exceed this
               nesting level will cause the current command to abort.
          GLOBIGNORE
               A colon-separated list of patterns defining the set of filenames
               to be ignored by pathname expansion.  If a filename matched by a
               pathname expansion pattern also matches one of the patterns in
               GLOBIGNORE, it is removed from the list of matches.
          HISTCONTROL
               A colon-separated list of values controlling how commands are
               saved on the history list.  If the list of values includes
               ignorespace, lines which begin with a space character are not
               saved in the history list.  A value of ignoredups causes lines
               matching the previous history entry to not be saved.  A value of
               ignoreboth is shorthand for ignorespace and ignoredups.  A value
               of erasedups causes all previous lines matching the current line
               to be removed from the history list before that line is saved.
               Any value not in the above list is ignored.  If HISTCONTROL is
               unset, or does not include a valid value, all lines read by the
               shell parser are saved on the history list, subject to the value
               of HISTIGNORE.  The second and subsequent lines of a multi-line
               compound command are not tested, and are added to the history
               regardless of the value of HISTCONTROL.
          HISTFILE
               The name of the file in which command history is saved (see
               HISTORY below).  The default value is ~/.bash_history.  If unset,
               the command history is not saved when a shell exits.
          HISTFILESIZE
               The maximum number of lines contained in the history file.  When
               this variable is assigned a value, the history file is truncated,
               if necessary, to contain no more than that number of lines by
               removing the oldest entries.  The history file is also truncated
               to this size after writing it when a shell exits.  If the value
               is 0, the history file is truncated to zero size.  Non-numeric
               values and numeric values less than zero inhibit truncation.  The
               shell sets the default value to the value of HISTSIZE after
               reading any startup files.
          HISTIGNORE
               A colon-separated list of patterns used to decide which command
               lines should be saved on the history list.  Each pattern is
               anchored at the beginning of the line and must match the complete
               line (no implicit `*' is appended).  Each pattern is tested
               against the line after the checks specified by HISTCONTROL are

                                       - 22 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               applied.  In addition to the normal shell pattern matching
               characters, `&' matches the previous history line.  `&' may be
               escaped using a backslash; the backslash is removed before
               attempting a match.  The second and subsequent lines of a multi-
               line compound command are not tested, and are added to the
               history regardless of the value of HISTIGNORE.
          HISTSIZE
               The number of commands to remember in the command history (see
               HISTORY below).  If the value is 0, commands are not saved in the
               history list.  Numeric values less than zero result in every
               command being saved on the history list (there is no limit).  The
               shell sets the default value to 500 after reading any startup
               files.
          HISTTIMEFORMAT
               If this variable is set and not null, its value is used as a
               format string for strftime(3) to print the time stamp associated
               with each history entry displayed by the history builtin.  If
               this variable is set, time stamps are written to the history file
               so they may be preserved across shell sessions.  This uses the
               history comment character to distinguish timestamps from other
               history lines.
          HOME The home directory of the current user; the default argument for
               the cd builtin command.  The value of this variable is also used
               when performing tilde expansion.
          HOSTFILE
               Contains the name of a file in the same format as /etc/hosts that
               should be read when the shell needs to complete a hostname.  The
               list of possible hostname completions may be changed while the
               shell is running; the next time hostname completion is attempted
               after the value is changed, bash adds the contents of the new
               file to the existing list.  If HOSTFILE is set, but has no value,
               or does not name a readable file, bash attempts to read
               /etc/hosts to obtain the list of possible hostname completions.
               When HOSTFILE is unset, the hostname list is cleared.
          IFS  The Internal Field Separator that is used for word splitting
               after expansion and to split lines into words with the read
               builtin command.  The default value is ``<space><tab><newline>''.
          IGNOREEOF
               Controls the action of an interactive shell on receipt of an EOF
               character as the sole input.  If set, the value is the number of
               consecutive EOF characters which must be typed as the first
               characters on an input line before bash exits.  If the variable
               exists but does not have a numeric value, or has no value, the
               default value is 10.  If it does not exist, EOF signifies the end
               of input to the shell.
          INPUTRC
               The filename for the readline startup file, overriding the
               default of ~/.inputrc (see READLINE below).
          LANG Used to determine the locale category for any category not
               specifically selected with a variable starting with LC_.

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          LC_ALL
               This variable overrides the value of LANG and any other LC_
               variable specifying a locale category.
          LC_COLLATE
               This variable determines the collation order used when sorting
               the results of pathname expansion, and determines the behavior of
               range expressions, equivalence classes, and collating sequences
               within pathname expansion and pattern matching.
          LC_CTYPE
               This variable determines the interpretation of characters and the
               behavior of character classes within pathname expansion and
               pattern matching.
          LC_MESSAGES
               This variable determines the locale used to translate double-
               quoted strings preceded by a $.
          LC_NUMERIC
               This variable determines the locale category used for number
               formatting.
          LINES
               Used by the select compound command to determine the column
               length for printing selection lists.  Automatically set if the
               checkwinsize option is enabled or in an interactive shell upon
               receipt of a SIGWINCH.
          MAIL If this parameter is set to a file or directory name and the
               MAILPATH variable is not set, bash informs the user of the
               arrival of mail in the specified file or Maildir-format
               directory.
          MAILCHECK
               Specifies how often (in seconds) bash checks for mail.  The
               default is 60 seconds.  When it is time to check for mail, the
               shell does so before displaying the primary prompt.  If this
               variable is unset, or set to a value that is not a number greater
               than or equal to zero, the shell disables mail checking.
          MAILPATH
               A colon-separated list of filenames to be checked for mail. The
               message to be printed when mail arrives in a particular file may
               be specified by separating the filename from the message with a
               `?'.  When used in the text of the message, $_ expands to the
               name of the current mailfile. Example:
               MAILPATH=/var/mail/bfox?"You have mail":~/shell-mail?"$_ has
               mail!"
               Bash supplies a default value for this variable, but the location
               of the user mail files that it uses is system dependent (e.g.,
               /var/mail/$USER).
          OPTERR
               If set to the value 1, bash displays error messages generated by
               the getopts builtin command (see SHELL BUILTIN COMMANDS below).
               OPTERR is initialized to 1 each time the shell is invoked or a
               shell script is executed.
          PATH The search path for commands.  It is a colon-separated list of
               directories in which the shell looks for commands (see COMMAND

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               EXECUTION below).  A zero-length (null) directory name in the
               value of PATH indicates the current directory.  A null directory
               name may appear as two adjacent colons, or as an initial or
               trailing colon.  The default path is system-dependent, and is set
               by the administrator who installs bash.  A common value is
               ``/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
          POSIXLY_CORRECT
               If this variable is in the environment when bash starts, the
               shell enters posix mode before reading the startup files, as if
               the --posix invocation option had been supplied.  If it is set
               while the shell is running, bash enables posix mode, as if the
               command set -o posix had been executed.
          PROMPT_COMMAND
               If set, the value is executed as a command prior to issuing each
               primary prompt.
          PROMPT_DIRTRIM
               If set to a number greater than zero, the value is used as the
               number of trailing directory components to retain when expanding
               the \w and \W prompt string escapes (see PROMPTING below).
               Characters removed are replaced with an ellipsis.
          PS1  The value of this parameter is expanded (see PROMPTING below) and
               used as the primary prompt string.  The default value is
               ``\s-\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

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               indicates that the remainder of the line is a comment when found
               as the first character of a word, normally `#'.  The history
               comment character causes history substitution to be skipped for
               the remaining words on the line.  It does not necessarily cause
               the shell parser to treat the rest of the line as a comment.

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

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

          Associative arrays are created using declare -A name.

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

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

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

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

          Any element of an array may be referenced using ${name[subscript]}.
          The braces are required to avoid conflicts with pathname expansion.
          If subscript is @ or *, the word expands to all members of name.
          These subscripts differ only when the word appears within double

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

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

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

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

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

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

          The order of expansions is: brace expansion; tilde expansion,
          parameter and variable expansion, arithmetic expansion, and command

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                                   2014 February 2

          substitution (done in a left-to-right fashion); word splitting; and
          pathname expansion.

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

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

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

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

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

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

          A correctly-formed brace expansion must contain unquoted opening and
          closing braces, and at least one unquoted comma or a valid sequence
          expression.  Any incorrectly formed brace expansion is left unchanged.
          A { or , may be quoted with a backslash to prevent its being

                                       - 29 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          considered part of a brace expression.  To avoid conflicts with
          parameter expansion, the string ${ is not considered eligible for
          brace expansion.

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

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

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

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

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

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

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

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

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

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

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

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

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

          ${parameter:-word}
               Use Default Values.  If parameter is unset or null, the expansion
               of word is substituted.  Otherwise, the value of parameter is
               substituted.
          ${parameter:=word}
               Assign Default Values.  If parameter is unset or null, the
               expansion of word is assigned to parameter.  The value of
               parameter is then substituted.  Positional parameters and special
               parameters may not be assigned to in this way.
          ${parameter:?word}
               Display Error if Null or Unset.  If parameter is null or unset,
               the expansion of word (or a message to that effect if word is not
               present) is written to the standard error and the shell, if it is

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               not interactive, exits.  Otherwise, the value of parameter is
               substituted.
          ${parameter:+word}
               Use Alternate Value.  If parameter is null or unset, nothing is
               substituted, otherwise the expansion of word is substituted.
          ${parameter:offset}
          ${parameter:offset:length}
               Substring Expansion.  Expands to up to length characters of the
               value of parameter starting at the character specified by offset.
               If parameter is @, an indexed array subscripted by @ or *, or an
               associative array name, the results differ as described below.
               If length is omitted, expands to the substring of the value of
               parameter starting at the character specified by offset and
               extending to the end of the value.  length and offset are
               arithmetic expressions (see ARITHMETIC EVALUATION below).

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

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

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

               Substring expansion applied to an associative array produces
               undefined results.

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

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

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               word.

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

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

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

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

          ${parameter/pattern/string}
               Pattern substitution.  The pattern is expanded to produce a

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

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

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

               $(command)
          or
               `command`

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

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

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

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

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

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

          The shell treats each character of IFS as a delimiter, and splits the
          results of the other expansions into words using these characters as

                                       - 35 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

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

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

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

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

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          Pattern Matching

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

          The special pattern characters have the following meanings:

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

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

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

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

                                       - 37 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

                    symbol symbol.

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

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

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

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

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

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

          The word following the redirection operator in the following
          descriptions, unless otherwise noted, is subjected to brace expansion,
          tilde expansion, parameter and variable expansion, command

                                       - 38 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          substitution, arithmetic expansion, quote removal, pathname expansion,
          and word splitting.  If it expands to more than one word, bash reports
          an error.

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

               ls > dirlist 2>&1

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

               ls 2>&1 > dirlist

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

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

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

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

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

        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:

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               [n]<word

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

          The general format for redirecting output is:

               [n]>word

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

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

          The general format for appending output is:

               [n]>>word

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

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

               &>word
          and
               >&word

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

               >word 2>&1

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

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                                   2014 February 2

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

          The format for appending standard output and standard error is:

               &>>word

          This is semantically equivalent to

               >>word 2>&1

          (see Duplicating File Descriptors below).

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

          The format of here-documents is:

               <<[-]word
                       here-document
               delimiter

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

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

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

               <<<word

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

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                                   2014 February 2

        Duplicating File Descriptors
          The redirection operator

               [n]<&word

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

          The operator

               [n]>&word

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

        Moving File Descriptors
          The redirection operator

               [n]<&digit-

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

          Similarly, the redirection operator

               [n]>&digit-

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

        Opening File Descriptors for Reading and Writing
          The redirection operator

               [n]<>word

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

     ALIASES
          Aliases allow a string to be substituted for a word when it is used as

                                       - 42 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          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

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          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

                                       - 44 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          for overflow, though division by 0 is trapped and flagged as an error.
          The operators and their precedence, associativity, and values are the
          same as in the C language.  The following list of operators is grouped
          into levels of equal-precedence operators.  The levels are listed in
          order of decreasing precedence.

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

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

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

                                       - 45 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          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.

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          -u file
               True if file exists and its set-user-id bit is set.
          -w file
               True if file exists and is writable.
          -x file
               True if file exists and is executable.
          -G file
               True if file exists and is owned by the effective group id.
          -L file
               True if file exists and is a symbolic link.
          -N file
               True if file exists and has been modified since it was last read.
          -O file
               True if file exists and is owned by the effective user id.
          -S file
               True if file exists and is a socket.
          file1 -ef file2
               True if file1 and file2 refer to the same device and inode
               numbers.
          file1 -nt file2
               True if file1 is newer (according to modification date) than
               file2, or if file1 exists and file2 does not.
          file1 -ot file2
               True if file1 is older than file2, or if file2 exists and file1
               does not.
          -o optname
               True if the shell option optname is enabled.  See the list of
               options under the description of the -o option to the set builtin
               below.
          -v varname
               True if the shell variable varname is set (has been assigned a
               value).
          -R varname
               True if the shell variable varname is set and is a name
               reference.
          -z string
               True if the length of string is zero.
          string
          -n string
               True if the length of string is non-zero.

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

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

                                       - 47 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          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.

                                       - 48 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

     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:

                                       - 49 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

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

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

          o    current traps set by trap

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

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

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

          o    options enabled by shopt

          o    shell aliases defined with alias

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

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

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

          o    the current working directory

          o    the file creation mode mask

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

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

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

          Command substitution, commands grouped with parentheses, and
          asynchronous commands are invoked in a subshell environment that is a

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

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

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

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

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

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

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

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

     EXIT STATUS
          The exit status of an executed command is the value returned by the
          waitpid system call or equivalent function.  Exit statuses fall
          between 0 and 255, though, as explained below, the shell may use

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          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.

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          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

                                       - 53 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

          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

                                       - 54 -         Formatted:  April 10, 2015

     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

                    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.

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

        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).

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                                   2014 February 2

        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

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

               \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.
          colored-stats (Off)
               If set to On, readline displays possible completions using
               different colors to indicate their file type. The color
               definitions are taken from the value of the LS_COLORS environment
               variable.
          comment-begin (``#'')
               The string that is inserted when the readline insert-comment
               command is executed.  This command is bound to M-# in emacs mode
               and to # in vi command mode.
          completion-ignore-case (Off)
               If set to On, readline performs filename matching and completion
               in a case-insensitive fashion.

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          completion-prefix-display-length (0)
               The length in characters of the common prefix of a list of
               possible completions that is displayed without modification.
               When set to a value greater than zero, common prefixes longer
               than this value are replaced with an ellipsis when displaying
               possible completions.
          completion-query-items (100)
               This determines when the user is queried about viewing the number
               of possible completions generated by the possible-completions
               command.  It may be set to any integer value greater than or
               equal to zero.  If the number of possible completions is greater
               than or equal to the value of this variable, the user is asked
               whether or not he wishes to view them; otherwise they are simply
               listed on the terminal.
          convert-meta (On)
               If set to On, readline will convert characters with the eighth
               bit set to an ASCII key sequence by stripping the eighth bit and
               prefixing an escape character (in effect, using escape as the
               meta prefix).
          disable-completion (Off)
               If set to On, readline will inhibit word completion.  Completion
               characters will be inserted into the line as if they had been
               mapped to self-insert.
          editing-mode (emacs)
               Controls whether readline begins with a set of key bindings
               similar to Emacs or vi.  editing-mode can be set to either emacs
               or vi.
          echo-control-characters (On)
               When set to On, on operating systems that indicate they support
               it, readline echoes a character corresponding to a signal
               generated from the keyboard.
          enable-keypad (Off)
               When set to On, readline will try to enable the application
               keypad when it is called.  Some systems need this to enable the
               arrow keys.
          enable-meta-key (On)
               When set to On, readline will try to enable any meta modifier key
               the terminal claims to support when it is called.  On many
               terminals, the meta key is used to send eight-bit characters.
          expand-tilde (Off)
               If set to On, tilde expansion is performed when readline attempts
               word completion.
          history-preserve-point (Off)
               If set to On, the history code attempts to place point at the
               same location on each history line retrieved with previous-
               history or next-history.
          history-size (0)
               Set the maximum number of history entries saved in the history
               list.  If set to zero, any existing history entries are deleted
               and no new entries are saved.  If set to a value less than zero,
               the number of history entries is not limited.  By default, the

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               number of history entries is not limited.
          horizontal-scroll-mode (Off)
               When set to On, makes readline use a single line for display,
               scrolling the input horizontally on a single screen line when it
               becomes longer than the screen width rather than wrapping to a
               new line.
          input-meta (Off)
               If set to On, readline will enable eight-bit input (that is, it
               will not strip the high bit from the characters it reads),
               regardless of what the terminal claims it can support.  The name
               meta-flag is a synonym for this variable.
          isearch-terminators (``C-[C-J'')
               The string of characters that should terminate an incremental
               search without subsequently executing the character as a command.
               If this variable has not been given a value, the characters ESC
               and C-J will terminate an incremental search.
          keymap (emacs)
               Set the current readline keymap.  The set of valid keymap names
               is emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi-command,
               and vi-insert.  vi is equivalent to vi-command; emacs is
               equivalent to emacs-standard.  The default value is emacs; the
               value of editing-mode also affects the default keymap.
          keyseq-timeout (500)
               Specifies the duration readline will wait for a character when
               reading an ambiguous key sequence (one that can form a complete
               key sequence using the input read so far, or can take additional
               input to complete a longer key sequence).  If no input is
               received within the timeout, readline will use the shorter but
               complete key sequence.  The value is specified in milliseconds,
               so a value of 1000 means that readline will wait one second for
               additional input.  If this variable is set to a value less than
               or equal to zero, or to a non-numeric value, readline will wait
               until another key is pressed to decide which key sequence to
               complete.
          mark-directories (On)
               If set to On, completed directory names have a slash appended.
          mark-modified-lines (Off)
               If set to On, history lines that have been modified are displayed
               with a preceding asterisk (*).
          mark-symlinked-directories (Off)
               If set to On, completed names which are symbolic links to
               directories have a slash appended (subject to the value of
               mark-directories).
          match-hidden-files (On)
               This variable, when set to On, causes readline to match files
               whose names begin with a `.' (hidden files) when performing
               filename completion.  If set to Off, the leading `.' must be
               supplied by the user in the filename to be completed.
          menu-complete-display-prefix (Off)
               If set to On, menu completion displays the common prefix of the
               list of possible completions (which may be empty) before cycling

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                                   2014 February 2

               through the list.
          output-meta (Off)
               If set to On, readline will display characters with the eighth
               bit set directly rather than as a meta-prefixed escape sequence.
          page-completions (On)
               If set to On, readline uses an internal more-like pager to
               display a screenful of possible completions at a time.
          print-completions-horizontally (Off)
               If set to On, readline will display completions with matches
               sorted horizontally in alphabetical order, rather than down the
               screen.
          revert-all-at-newline (Off)
               If set to On, readline will undo all changes to history lines
               before returning when accept-line is executed.  By default,
               history lines may be modified and retain individual undo lists
               across calls to readline.
          show-all-if-ambiguous (Off)
               This alters the default behavior of the completion functions.  If
               set to On, words which have more than one possible completion
               cause the matches to be listed immediately instead of ringing the
               bell.
          show-all-if-unmodified (Off)
               This alters the default behavior of the completion functions in a
               fashion similar to show-all-if-ambiguous.  If set to On, words
               which have more than one possible completion without any possible
               partial completion (the possible completions don't share a common
               prefix) cause the matches to be listed immediately instead of
               ringing the bell.
          show-mode-in-prompt (Off)
               If set to On, add a character to the beginning of the prompt
               indicating the editing mode: emacs (@), vi command (:) or vi
               insertion (+).
          skip-completed-text (Off)
               If set to On, this alters the default completion behavior when
               inserting a single match into the line.  It's only active when
               performing completion in the middle of a word.  If enabled,
               readline does not insert characters from the completion that
               match characters after point in the word being completed, so
               portions of the word following the cursor are not duplicated.
          visible-stats (Off)
               If set to On, a character denoting a file's type as reported by
               stat(2) is appended to the filename when listing possible
               completions.

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

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          $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.

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          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).

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          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.

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          yank-nth-arg (M-C-y)
               Insert the first argument to the previous command (usually the
               second word on the previous line) at point.  With an argument n,
               insert the nth word from the previous command (the words in the
               previous command begin with word 0).  A negative argument inserts
               the nth word from the end of the previous command.  Once the
               argument n is computed, the argument is extracted as if the "!n"
               history expansion had been specified.
          yank-last-arg (M-., M-_)
               Insert the last argument to the previous command (the last word
               of the previous history entry).  With a numeric argument, behave
               exactly like yank-nth-arg.  Successive calls to yank-last-arg
               move back through the history list, inserting the last word (or
               the word specified by the argument to the first call) of each
               line in turn.  Any numeric argument supplied to these successive
               calls determines the direction to move through the history.  A
               negative argument switches the direction through the history
               (back or forward).  The history expansion facilities are used to
               extract the last word, as if the "!$" history expansion had been
               specified.
          shell-expand-line (M-C-e)
               Expand the line as the shell does.  This performs alias and
               history expansion as well as all of the shell word expansions.
               See HISTORY EXPANSION below for a description of history
               expansion.
          history-expand-line (M-^)
               Perform history expansion on the current line.  See HISTORY
               EXPANSION below for a description of history expansion.
          magic-space
               Perform history expansion on the current line and insert a space.
               See HISTORY EXPANSION below for a description of history
               expansion.
          alias-expand-line
               Perform alias expansion on the current line.  See ALIASES above
               for a description of alias expansion.
          history-and-alias-expand-line
               Perform history and alias expansion on the current line.
          insert-last-argument (M-., M-_)
               A synonym for yank-last-arg.
          operate-and-get-next (C-o)
               Accept the current line for execution and fetch the next line
               relative to the current line from the history for editing.  Any
               argument is ignored.
          edit-and-execute-command (C-xC-e)
               Invoke an editor on the current command line, and execute the
               result as shell commands.  Bash attempts to invoke $VISUAL,
               $EDITOR, and emacs as the editor, in that order.

        Commands for Changing Text
          end-of-file (usually C-d)
               The character indicating end-of-file as set, for example, by

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                                   2014 February 2

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

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        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.

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        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.

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          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.

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          call-last-kbd-macro (C-x e)
               Re-execute the last keyboard macro defined, by making the
               characters in the macro appear as if typed at the keyboard.
          print-last-kbd-macro ()
               Print the last keyboard macro defined in a format suitable for
               the inputrc file.

        Miscellaneous
          re-read-init-file (C-x C-r)
               Read in the contents of the inputrc file, and incorporate any
               bindings or variable assignments found there.
          abort (C-g)
               Abort the current editing command and ring the terminal's bell
               (subject to the setting of bell-style).
          do-uppercase-version (M-a, M-b, M-x, ...)
               If the metafied character x is lowercase, run the command that is
               bound to the corresponding uppercase character.
          prefix-meta (ESC)
               Metafy the next character typed.  ESC f is equivalent to Meta-f.
          undo (C-_, C-x C-u)
               Incremental undo, separately remembered for each line.
          revert-line (M-r)
               Undo all changes made to this line.  This is like executing the
               undo command enough times to return the line to its initial
               state.
          tilde-expand (M-&)
               Perform tilde expansion on the current word.
          set-mark (C-@, M-<space>)
               Set the mark to the point.  If a numeric argument is supplied,
               the mark is set to that position.
          exchange-point-and-mark (C-x C-x)
               Swap the point with the mark.  The current cursor position is set
               to the saved position, and the old cursor position is saved as
               the mark.
          character-search (C-])
               A character is read and point is moved to the next occurrence of
               that character.  A negative count searches for previous
               occurrences.
          character-search-backward (M-C-])
               A character is read and point is moved to the previous occurrence
               of that character.  A negative count searches for subsequent
               occurrences.
          skip-csi-sequence
               Read enough characters to consume a multi-key sequence such as
               those defined for keys like Home and End.  Such sequences begin
               with a Control Sequence Indicator (CSI), usually ESC-[.  If this
               sequence is bound to "\[", keys producing such sequences will
               have no effect unless explicitly bound to a readline command,
               instead of inserting stray characters into the editing buffer.
               This is unbound by default, but usually bound to ESC-[.

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          insert-comment (M-#)
               Without a numeric argument, the value of the readline
               comment-begin variable is inserted at the beginning of the
               current line.  If a numeric argument is supplied, this command
               acts as a toggle:  if the characters at the beginning of the line
               do not match the value of comment-begin, the value is inserted,
               otherwise the characters in comment-begin are deleted from the
               beginning of the line.  In either case, the line is accepted as
               if a newline had been typed.  The default value of comment-begin
               causes this command to make the current line a shell comment.  If
               a numeric argument causes the comment character to be removed,
               the line will be executed by the shell.
          glob-complete-word (M-g)
               The word before point is treated as a pattern for pathname
               expansion, with an asterisk implicitly appended.  This pattern is
               used to generate a list of matching filenames for possible
               completions.
          glob-expand-word (C-x *)
               The word before point is treated as a pattern for pathname
               expansion, and the list of matching filenames is inserted,
               replacing the word.  If a numeric argument is supplied, an
               asterisk is appended before pathname expansion.
          glob-list-expansions (C-x g)
               The list of expansions that would have been generated by
               glob-expand-word is displayed, and the line is redrawn.  If a
               numeric argument is supplied, an asterisk is appended before
               pathname expansion.
          dump-functions
               Print all of the functions and their key bindings to the readline
               output stream.  If a numeric argument is supplied, the output is
               formatted in such a way that it can be made part of an inputrc
               file.
          dump-variables
               Print all of the settable readline variables and their values to
               the readline output stream.  If a numeric argument is supplied,
               the output is formatted in such a way that it can be made part of
               an inputrc file.
          dump-macros
               Print all of the readline key sequences bound to macros and the
               strings they output.  If a numeric argument is supplied, the
               output is formatted in such a way that it can be made part of an
               inputrc file.
          display-shell-version (C-x C-v)
               Display version information about the current instance of bash.

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

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

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

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

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

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

          After these matches have been generated, any shell function or command
          specified with the -F and -C options is invoked.  When the command or
          function is invoked, the COMP_LINE, COMP_POINT, COMP_KEY, and
          COMP_TYPE variables are assigned values as described above under Shell
          Variables.  If a shell function is being invoked, the COMP_WORDS and
          COMP_CWORD variables are also set.  When the function or command is
          invoked, the first argument ($1) is the name of the command whose
          arguments are being completed, the second argument ($2) is the word
          being completed, and the third argument ($3) is the word preceding the
          word being completed on the current command line.  No filtering of the
          generated completions against the word being completed is performed;
          the function or command has complete freedom in generating the
          matches.

          Any function specified with -F is invoked first.  The function may use
          any of the shell facilities, including the compgen builtin described

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          below, to generate the matches.  It must put the possible completions
          in the COMPREPLY array variable, one per array element.

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

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

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

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

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

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

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

          There is some support for dynamically modifying completions.  This is
          most useful when used in combination with a default completion
          specified with complete -D.  It's possible for shell functions
          executed as completion handlers to indicate that completion should be

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          retried by returning an exit status of 124.  If a shell function
          returns 124, and changes the compspec associated with the command on
          which completion is being attempted (supplied as the first argument
          when the function is executed), programmable completion restarts from
          the beginning, with an attempt to find a new compspec for that
          command.  This allows a set of completions to be built dynamically as
          completion is attempted, rather than being loaded all at once.

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

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

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

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

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          than HISTFILESIZE lines.  If HISTFILESIZE is unset, or set to null, a
          non-numeric value, or a numeric value less than zero, the history file
          is not truncated.

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

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

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

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

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

          Several characters inhibit history expansion if found immediately
          following the history expansion character, even if it is unquoted:

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          space, tab, newline, carriage return, and =.  If the extglob shell
          option is enabled, ( will also inhibit expansion.

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

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

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

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

          ^string1^string2^
               Quick substitution.  Repeat the previous command, replacing
               string1 with string2.  Equivalent to ``!!:s/string1/string2/''
               (see Modifiers below).
          !#   The entire command line typed so far.

        Word Designators
          Word designators are used to select desired words from the event.  A :
          separates the event specification from the word designator.  It may be
          omitted if the word designator begins with a ^, $, *, -, or %.  Words
          are numbered from the beginning of the line, with the first word being

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                                   2014 February 2

          denoted by 0 (zero).  Words are inserted into the current line
          separated by single spaces.

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

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

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

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

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     SHELL BUILTIN COMMANDS
          Unless otherwise noted, each builtin command documented in this
          section as accepting options preceded by - accepts -- to signify the
          end of the options.  The :, true, false, and test builtins do not
          accept options and do not treat -- specially.  The exit, logout,
          break, continue, let, and shift builtins accept and process arguments
          beginning with - without requiring --.  Other builtins that accept
          arguments but are not specified as accepting options interpret
          arguments beginning with - as invalid options and require -- to
          prevent this interpretation.

          : [arguments]
               No effect; the command does nothing beyond expanding arguments
               and performing any specified redirections.  A zero exit code is
               returned.

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

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

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

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

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

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

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

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

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

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               successful, the absolute pathname of the new working directory is
               written to the standard output.  The return value is true if the
               directory was successfully changed; false otherwise.

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

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

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

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

     [-W wordlist] [-F function] [-C command]
          complete [-abcdefgjksuv] [-o comp-
               option] [-DE] [-A action] [-G globpat]
               [-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

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               apply to ``empty'' command completion; that is, completion
               attempted on a blank line.

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

               Other options, if specified, have the following meanings.  The
               arguments to the -G, -W, and -X options (and, if necessary, the
               -P and -S options) should be quoted to protect them from
               expansion before the complete builtin is invoked.
               -o comp-option
                       The comp-option controls several aspects of the
                       compspec's behavior beyond the simple generation of
                       completions.  comp-option may be one of:
                       bashdefault
                               Perform the rest of the default bash completions
                               if the compspec generates no matches.
                       default Use readline's default filename completion if the
                               compspec generates no matches.
                       dirnames
                               Perform directory name completion if the compspec
                               generates no matches.
                       filenames
                               Tell readline that the compspec generates
                               filenames, so it can perform any
                               filename-specific processing (like adding a slash
                               to directory names, quoting special characters,
                               or suppressing trailing spaces).  Intended to be
                               used with shell functions.
                       noquote Tell readline not to quote the completed words if
                               they are filenames (quoting filenames is the
                               default).
                       nospace Tell readline not to append a space (the default)
                               to words completed at the end of the line.
                       plusdirs
                               After any matches defined by the compspec are
                               generated, directory name completion is attempted
                               and any matches are added to the results of the
                               other actions.
               -A action
                       The action may be one of the following to generate a list
                       of possible completions:
                       alias   Alias names.  May also be specified as -a.
                       arrayvar
                               Array variable names.
                       binding Readline key binding names.
                       builtin Names of shell builtin commands.  May also be
                               specified as -b.
                       command Command names.  May also be specified as -c.

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                       directory
                               Directory names.  May also be specified as -d.
                       disabled
                               Names of disabled shell builtins.
                       enabled Names of enabled shell builtins.
                       export  Names of exported shell variables.  May also be
                               specified as -e.
                       file    File names.  May also be specified as -f.
                       function
                               Names of shell functions.
                       group   Group names.  May also be specified as -g.
                       helptopic
                               Help topics as accepted by the help builtin.
                       hostname
                               Hostnames, as taken from the file specified by
                               the HOSTFILE shell variable.
                       job     Job names, if job control is active.  May also be
                               specified as -j.
                       keyword Shell reserved words.  May also be specified as
                               -k.
                       running Names of running jobs, if job control is active.
                       service Service names.  May also be specified as -s.
                       setopt  Valid arguments for the -o option to the set
                               builtin.
                       shopt   Shell option names as accepted by the shopt
                               builtin.
                       signal  Signal names.
                       stopped Names of stopped jobs, if job control is active.
                       user    User names.  May also be specified as -u.
                       variable
                               Names of all shell variables.  May also be
                               specified as -v.
               -C command
                       command is executed in a subshell environment, and its
                       output is used as the possible completions.
               -F function
                       The shell function function is executed in the current
                       shell environment.  When the function is executed, the
                       first argument ($1) is the name of the command whose
                       arguments are being completed, the second argument ($2)
                       is the word being completed, and the third argument ($3)
                       is the word preceding the word being completed on the
                       current command line.  When it finishes, the possible
                       completions are retrieved from the value of the COMPREPLY
                       array variable.
               -G globpat
                       The pathname expansion pattern globpat is expanded to
                       generate the possible completions.
               -P prefix
                       prefix is added at the beginning of each possible
                       completion after all other options have been applied.

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               -S suffix
                       suffix is appended to each possible completion after all
                       other options have been applied.
               -W wordlist
                       The wordlist is split using the characters in the IFS
                       special variable as delimiters, and each resultant word
                       is expanded.  The possible completions are the members of
                       the resultant list which match the word being completed.
               -X filterpat
                       filterpat is a pattern as used for pathname expansion.
                       It is applied to the list of possible completions
                       generated by the preceding options and arguments, and
                       each completion matching filterpat is removed from the
                       list.  A leading ! in filterpat negates the pattern; in
                       this case, any completion not matching filterpat is
                       removed.

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

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

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

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

          declare [-aAfFgilnrtux] [-p] [name[=value] ...]
          typeset [-aAfFgilnrtux] [-p] [name[=value] ...]
               Declare variables and/or give them attributes.  If no names are

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

               Using `+' instead of `-' turns off the attribute instead, with
               the exceptions that +a may not be used to destroy an array
               variable and +r will not remove the readonly attribute.  When
               used in a function, declare and typeset make each name local, as
               with the local command, unless the -g option is supplied.  If a

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               variable name is followed by =value, the value of the variable is
               set to value.  When using -a or -A and the compound assignment
               syntax to create array variables, additional attributes do not
               take effect until subsequent assignments.  The return value is 0
               unless an invalid option is encountered, an attempt is made to
               define a function using ``-f foo=bar'', an attempt is made to
               assign a value to a readonly variable, an attempt is made to
               assign a value to an array variable without using the compound
               assignment syntax (see Arrays above), one of the names is not a
               valid shell variable name, an attempt is made to turn off
               readonly status for a readonly variable, an attempt is made to
               turn off array status for an array variable, or an attempt is
               made to display a non-existent function with -f.

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

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

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

          echo [-neE] [arg ...]
               Output the args, separated by spaces, followed by a newline.  The
               return status is 0 unless a write error occurs.  If -n is
               specified, the trailing newline is suppressed.  If the -e option

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               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.

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

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

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

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

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

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               -16 for listing.

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

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

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

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

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

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

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

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

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

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

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

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

          help [-dms] [pattern]
               Display helpful information about builtin commands.  If pattern
               is specified, help gives detailed help on all commands matching
               pattern; otherwise help for all the builtins and shell control
               structures is printed.

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               -d   Display a short description of each pattern
               -m   Display the description of each pattern in a manpage-like
                    format
               -s   Display only a short usage synopsis for each pattern

               The return status is 0 unless no command matches pattern.

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

               If the HISTTIMEFORMAT variable is set, the time stamp information
               associated with each history entry is written to the history
               file, marked with the history comment character.  When the
               history file is read, lines beginning with the history comment
               character followed immediately by a digit are interpreted as
               timestamps for the previous history line.  The return value is 0

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               unless an invalid option is encountered, an error occurs while
               reading or writing the history file, an invalid offset is
               supplied as an argument to -d, or the history expansion supplied
               as an argument to -p fails.

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

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

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

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

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

          local [option] [name[=value] ...]
               For each argument, a local variable named name is created, and
               assigned value.  The option can be any of the options accepted by
               declare.  When local is used within a function, it causes the
               variable name to have a visible scope restricted to that function
               and its children.  With no operands, local writes a list of local
               variables to the standard output.  It is an error to use local

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               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.

     quantum] [array]
          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
               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''

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                    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.  If no argument is
                    specified, conversion behaves as if -1 had been given.  This
                    is an exception to the usual printf behavior.

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

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

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

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

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

     prompt] [-t timeout] [-u fd] [name ...]
          read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p
               One line is read from the standard input, or from the file
               descriptor fd supplied as an argument to the -u option, and the
               first word is assigned to the first name, the second word to the
               second name, and so on, with leftover words and their intervening
               separators assigned to the last name.  If there are fewer words
               read from the input stream than names, the remaining names are
               assigned empty values.  The characters in IFS are used to split
               the line into words using the same rules the shell uses for
               expansion (described above under Word Splitting).  The backslash
               character (\) may be used to remove any special meaning for the
               next character read and for line continuation.  Options, if
               supplied, have the following meanings:

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                                   2014 February 2

               -a aname
                    The words are assigned to sequential indices of the array
                    variable aname, starting at 0.  aname is unset before any
                    new values are assigned.  Other name arguments are ignored.
               -d delim
                    The first character of delim is used to terminate the input
                    line, rather than newline.
               -e   If the standard input is coming from a terminal, readline
                    (see READLINE above) is used to obtain the line.  Readline
                    uses the current (or default, if line editing was not
                    previously active) editing settings.
               -i text
                    If readline is being used to read the line, text is placed
                    into the editing buffer before editing begins.
               -n nchars
                    read returns after reading nchars characters rather than
                    waiting for a complete line of input, but honor a delimiter
                    if fewer than nchars characters are read before the
                    delimiter.
               -N nchars
                    read returns after reading exactly nchars characters rather
                    than waiting for a complete line of input, unless EOF is
                    encountered or read times out.  Delimiter characters
                    encountered in the input are not treated specially and do
                    not cause read to return until nchars characters are read.
               -p prompt
                    Display prompt on standard error, without a trailing
                    newline, before attempting to read any input.  The prompt is
                    displayed only if input is coming from a terminal.
               -r   Backslash does not act as an escape character.  The
                    backslash is considered to be part of the line.  In
                    particular, a backslash-newline pair may not be used as a
                    line continuation.
               -s   Silent mode.  If input is coming from a terminal, characters
                    are not echoed.
               -t timeout
                    Cause read to time out and return failure if a complete line
                    of input (or a specified number of characters) is not read
                    within timeout seconds.  timeout may be a decimal number
                    with a fractional portion following the decimal point.  This
                    option is only effective if read is reading input from a
                    terminal, pipe, or other special file; it has no effect when
                    reading from regular files.  If read times out, read saves
                    any partial input read into the specified variable name.  If
                    timeout is 0, read returns immediately, without trying to
                    read any data.  The exit status is 0 if input is available
                    on the specified file descriptor, non-zero otherwise.  The
                    exit status is greater than 128 if the timeout is exceeded.
               -u fd
                    Read input from file descriptor fd.

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

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

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

          set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]
          set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg ...]
               Without options, the name and value of each shell variable are
               displayed in a format that can be reused as input for setting or
               resetting the currently-set variables.  Read-only variables
               cannot be reset.  In posix mode, only shell variables are listed.
               The output is sorted according to the current locale.  When
               options are specified, they set or unset shell attributes.  Any
               arguments remaining after option processing are treated as values
               for the positional parameters and are assigned, in order, to $1,
               $2, ... $n.  Options, if specified, have the following meanings:

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                                   2014 February 2

               -a      Automatically mark variables and functions which are
                       modified or created for export to the environment of
                       subsequent commands.
               -b      Report the status of terminated background jobs
                       immediately, rather than before the next primary prompt.
                       This is effective only when job control is enabled.
               -e      Exit immediately if a pipeline (which may consist of a
                       single simple command), a list, or a compound command
                       (see SHELL GRAMMAR above),  exits with a non-zero status.
                       The shell does not exit if the command that fails is part
                       of the command list immediately following a while or
                       until keyword, part of the test following the if or elif
                       reserved words, part of any command executed in a && or
                       || list except the command following the final && or ||,
                       any command in a pipeline but the last, or if the
                       command's return value is being inverted with !.  If a
                       compound command other than a subshell returns a non-zero
                       status because a command failed while -e was being
                       ignored, the shell does not exit.  A trap on ERR, if set,
                       is executed before the shell exits.  This option applies
                       to the shell environment and each subshell environment
                       separately (see COMMAND EXECUTION ENVIRONMENT above), and
                       may cause subshells to exit before executing all the
                       commands in the subshell.

                       If a compound command or shell function executes in a
                       context where -e is being ignored, none of the commands
                       executed within the compound command or function body
                       will be affected by the -e setting, even if -e is set and
                       a command returns a failure status.  If a compound
                       command or shell function sets -e while executing in a
                       context where -e is ignored, that setting will not have
                       any effect until the compound command or the command
                       containing the function call completes.
               -f      Disable pathname expansion.
               -h      Remember the location of commands as they are looked up
                       for execution.  This is enabled by default.
               -k      All arguments in the form of assignment statements are
                       placed in the environment for a command, not just those
                       that precede the command name.
               -m      Monitor mode.  Job control is enabled.  This option is on
                       by default for interactive shells on systems that support
                       it (see JOB CONTROL above).  All processes run in a
                       separate process group.  When a background job completes,
                       the shell prints a line containing its exit status.
               -n      Read commands but do not execute them.  This may be used
                       to check a shell script for syntax errors.  This is
                       ignored by interactive shells.
               -o option-name
                       The option-name can be one of the following:

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                                   2014 February 2

                       allexport
                               Same as -a.
                       braceexpand
                               Same as -B.
                       emacs   Use an emacs-style command line editing
                               interface.  This is enabled by default when the
                               shell is interactive, unless the shell is started
                               with the --noediting option.  This also affects
                               the editing interface used for read -e.
                       errexit Same as -e.
                       errtrace
                               Same as -E.
                       functrace
                               Same as -T.
                       hashall Same as -h.
                       histexpand
                               Same as -H.
                       history Enable command history, as described above under
                               HISTORY.  This option is on by default in
                               interactive shells.
                       ignoreeof
                               The effect is as if the shell command
                               ``IGNOREEOF=10'' had been executed (see Shell
                               Variables above).
                       keyword Same as -k.
                       monitor Same as -m.
                       noclobber
                               Same as -C.
                       noexec  Same as -n.
                       noglob  Same as -f.
                       nolog   Currently ignored.
                       notify  Same as -b.
                       nounset Same as -u.
                       onecmd  Same as -t.
                       physical
                               Same as -P.
                       pipefail
                               If set, the return value of a pipeline is the
                               value of the last (rightmost) command to exit
                               with a non-zero status, or zero if all commands
                               in the pipeline exit successfully.  This option
                               is disabled by default.
                       posix   Change the behavior of bash where the default
                               operation differs from the POSIX standard to
                               match the standard (posix mode).  See SEE ALSO
                               below for a reference to a document that details
                               how posix mode affects bash's behavior.
                       privileged
                               Same as -p.
                       verbose Same as -v.

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                       vi      Use a vi-style command line editing interface.
                               This also affects the editing interface used for
                               read -e.
                       xtrace  Same as -x.

                       If -o is supplied with no option-name, the values of the
                       current options are printed.  If +o is supplied with no
                       option-name, a series of set commands to recreate the
                       current option settings is displayed on the standard
                       output.
               -p      Turn on privileged mode.  In this mode, the $ENV and
                       $BASH_ENV files are not processed, shell functions are
                       not inherited from the environment, and the SHELLOPTS,
                       BASHOPTS, CDPATH, and GLOBIGNORE variables, if they
                       appear in the environment, are ignored.  If the shell is
                       started with the effective user (group) id not equal to
                       the real user (group) id, and the -p option is not
                       supplied, these actions are taken and the effective user
                       id is set to the real user id.  If the -p option is
                       supplied at startup, the effective user id is not reset.
                       Turning this option off causes the effective user and
                       group ids to be set to the real user and group ids.
               -t      Exit after reading and executing one command.
               -u      Treat unset variables and parameters other than the
                       special parameters "@" and "*" as an error when
                       performing parameter expansion.  If expansion is
                       attempted on an unset variable or parameter, the shell
                       prints an error message, and, if not interactive, exits
                       with a non-zero status.
               -v      Print shell input lines as they are read.
               -x      After expanding each simple command, for command, case
                       command, select command, or arithmetic for command,
                       display the expanded value of PS4, followed by the
                       command and its expanded arguments or associated word
                       list.
               -B      The shell performs brace expansion (see Brace Expansion
                       above).  This is on by default.
               -C      If set, bash does not overwrite an existing file with the
                       >, >&, and <> redirection operators.  This may be
                       overridden when creating output files by using the
                       redirection operator >| instead of >.
               -E      If set, any trap on ERR is inherited by shell functions,
                       command substitutions, and commands executed in a
                       subshell environment.  The ERR trap is normally not
                       inherited in such cases.
               -H      Enable ! style history substitution.  This option is on
                       by default when the shell is interactive.
               -P      If set, the shell does not resolve symbolic links when
                       executing commands such as cd that change the current
                       working directory.  It uses the physical directory
                       structure instead.  By default, bash follows the logical

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                       chain of directories when performing commands which
                       change the current directory.
               -T      If set, any traps on DEBUG and RETURN are inherited by
                       shell functions, command substitutions, and commands
                       executed in a subshell environment.  The DEBUG and RETURN
                       traps are normally not inherited in such cases.
               --      If no arguments follow this option, then the positional
                       parameters are unset.  Otherwise, the positional
                       parameters are set to the args, even if some of them
                       begin with a -.
               -       Signal the end of options, cause all remaining args to be
                       assigned to the positional parameters.  The -x and -v
                       options are turned off.  If there are no args, the
                       positional parameters remain unchanged.

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

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

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

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

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               default.

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

               The list of shopt options is:

               autocd  If set, a command name that is the name of a directory is
                       executed as if it were the argument to the cd command.
                       This option is only used by interactive shells.
               cdable_vars
                       If set, an argument to the cd builtin command that is not
                       a directory is assumed to be the name of a variable whose
                       value is the directory to change to.
               cdspell If set, minor errors in the spelling of a directory
                       component in a cd command will be corrected.  The errors
                       checked for are transposed characters, a missing
                       character, and one character too many.  If a correction
                       is found, the corrected filename is printed, and the
                       command proceeds.  This option is only used by
                       interactive shells.
               checkhash
                       If set, bash checks that a command found in the hash
                       table exists before trying to execute it.  If a hashed
                       command no longer exists, a normal path search is
                       performed.
               checkjobs
                       If set, bash lists the status of any stopped and running
                       jobs before exiting an interactive shell.  If any jobs
                       are running, this causes the exit to be deferred until a
                       second exit is attempted without an intervening command
                       (see JOB CONTROL above).  The shell always postpones
                       exiting if any jobs are stopped.
               checkwinsize
                       If set, bash checks the window size after each command
                       and, if necessary, updates the values of LINES and
                       COLUMNS.
               cmdhist If set, bash attempts to save all lines of a multiple-
                       line command in the same history entry.  This allows easy
                       re-editing of multi-line commands.
               compat31
                       If set, bash changes its behavior to that of version 3.1
                       with respect to quoted arguments to the [[ conditional
                       command's =~ operator and locale-specific string
                       comparison when using the [[ conditional command's < and
                       > operators.  Bash versions prior to bash-4.1 use ASCII
                       collation and strcmp(3); bash-4.1 and later use the
                       current locale's collation sequence and strcoll(3).

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               compat32
                       If set, bash changes its behavior to that of version 3.2
                       with respect to locale-specific string comparison when
                       using the [[ conditional command's < and > operators (see
                       previous item).
               compat40
                       If set, bash changes its behavior to that of version 4.0
                       with respect to locale-specific string comparison when
                       using the [[ conditional command's < and > operators (see
                       description of compat31) and the effect of interrupting a
                       command list.  Bash versions 4.0 and later interrupt the
                       list as if the shell received the interrupt; previous
                       versions continue with the next command in the list.
               compat41
                       If set, bash, when in posix mode, treats a single quote
                       in a double-quoted parameter expansion as a special
                       character.  The single quotes must match (an even number)
                       and the characters between the single quotes are
                       considered quoted.  This is the behavior of posix mode
                       through version 4.1.  The default bash behavior remains
                       as in previous versions.
               compat42
                       If set, bash does not process the replacement string in
                       the pattern substitution word expansion using quote
                       removal.
               complete_fullquote
                       If set, bash quotes all shell metacharacters in filenames
                       and directory names when performing completion.  If not
                       set, bash removes metacharacters such as the dollar sign
                       from the set of characters that will be quoted in
                       completed filenames when these metacharacters appear in
                       shell variable references in words to be completed.  This
                       means that dollar signs in variable names that expand to
                       directories will not be quoted; however, any dollar signs
                       appearing in filenames will not be quoted, either.  This
                       is active only when bash is using backslashes to quote
                       completed filenames.  This variable is set by default,
                       which is the default bash behavior in versions through
                       4.2.
               direxpand
                       If set, bash replaces directory names with the results of
                       word expansion when performing filename completion.  This
                       changes the contents of the readline editing buffer.  If
                       not set, bash attempts to preserve what the user typed.
               dirspell
                       If set, bash attempts spelling correction on directory
                       names during word completion if the directory name
                       initially supplied does not exist.
               dotglob If set, bash includes filenames beginning with a `.' in
                       the results of pathname expansion.

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               execfail
                       If set, a non-interactive shell will not exit if it
                       cannot execute the file specified as an argument to the
                       exec builtin command.  An interactive shell does not exit
                       if exec fails.
               expand_aliases
                       If set, aliases are expanded as described above under
                       ALIASES.  This option is enabled by default for
                       interactive shells.
               extdebug
                       If set, behavior intended for use by debuggers is
                       enabled:
                       1.   The -F option to the declare builtin displays the
                            source file name and line number corresponding to
                            each function name supplied as an argument.
                       2.   If the command run by the DEBUG trap returns a non-
                            zero value, the next command is skipped and not
                            executed.
                       3.   If the command run by the DEBUG trap returns a value
                            of 2, and the shell is executing in a subroutine (a
                            shell function or a shell script executed by the .
                            or source builtins), a call to return is simulated.
                       4.   BASH_ARGC and BASH_ARGV are updated as described in
                            their descriptions above.
                       5.   Function tracing is enabled:  command substitution,
                            shell functions, and subshells invoked with (
                            command ) inherit the DEBUG and RETURN traps.
                       6.   Error tracing is enabled:  command substitution,
                            shell functions, and subshells invoked with (
                            command ) inherit the ERR trap.
               extglob If set, the extended pattern matching features described
                       above under Pathname Expansion are enabled.
               extquote
                       If set, $string and $"string" quoting is performed within
                       ${parameter} expansions enclosed in double quotes.  This
                       option is enabled by default.
               failglob
                       If set, patterns which fail to match filenames during
                       pathname expansion result in an expansion error.
               force_fignore
                       If set, the suffixes specified by the FIGNORE shell
                       variable cause words to be ignored when performing word
                       completion even if the ignored words are the only
                       possible completions.  See SHELL VARIABLES above for a
                       description of FIGNORE.  This option is enabled by
                       default.
               globasciiranges
                       If set, range expressions used in pattern matching
                       bracket expressions (see Pattern Matching above) behave
                       as if in the traditional C locale when performing
                       comparisons.  That is, the current locale's collating

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

                       sequence is not taken into account, so b will not collate
                       between A and B, and upper-case and lower-case ASCII
                       characters will collate together.
               globstar
                       If set, the pattern ** used in a pathname expansion
                       context will match all files and zero or more directories
                       and subdirectories.  If the pattern is followed by a /,
                       only directories and subdirectories match.
               gnu_errfmt
                       If set, shell error messages are written in the standard
                       GNU error message format.
               histappend
                       If set, the history list is appended to the file named by
                       the value of the HISTFILE variable when the shell exits,
                       rather than overwriting the file.
               histreedit
                       If set, and readline is being used, a user is given the
                       opportunity to re-edit a failed history substitution.
               histverify
                       If set, and readline is being used, the results of
                       history substitution are not immediately passed to the
                       shell parser.  Instead, the resulting line is loaded into
                       the readline editing buffer, allowing further
                       modification.
               hostcomplete
                       If set, and readline is being used, bash will attempt to
                       perform hostname completion when a word containing a @ is
                       being completed (see Completing under READLINE above).
                       This is enabled by default.
               huponexit
                       If set, bash will send SIGHUP to all jobs when an
                       interactive login shell exits.
               interactive_comments
                       If set, allow a word beginning with # to cause that word
                       and all remaining characters on that line to be ignored
                       in an interactive shell (see COMMENTS above).  This
                       option is enabled by default.
               lastpipe
                       If set, and job control is not active, the shell runs the
                       last command of a pipeline not executed in the background
                       in the current shell environment.
               lithist If set, and the cmdhist option is enabled, multi-line
                       commands are saved to the history with embedded newlines
                       rather than using semicolon separators where possible.
               login_shell
                       The shell sets this option if it is started as a login
                       shell (see INVOCATION above).  The value may not be
                       changed.
               mailwarn
                       If set, and a file that bash is checking for mail has
                       been accessed since the last time it was checked, the

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

                       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.

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     BASH(1)                        GNU Bash 4.3                         BASH(1)
                                   2014 February 2

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

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

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

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

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               4 arguments
                    If the first argument is !, the result is the negation of
                    the three-argument expression composed of the remaining
                    arguments.  Otherwise, the expression is parsed and
                    evaluated according to precedence using the rules listed
                    above.
               5 or more arguments
                    The expression is parsed and evaluated according to
                    precedence using the rules listed above.

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

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

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

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

               If a sigspec is ERR, the command arg is executed whenever a a
               pipeline (which may consist of a single simple command), a list,
               or a compound command returns a non-zero exit status, subject to
               the following conditions.  The ERR trap is not executed if the
               failed command is part of the command list immediately following
               a while or until keyword, part of the test in an if statement,
               part of a command executed in a && or || list except the command

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                                   2014 February 2

               following the final && or ||, any command in a pipeline but the
               last, or if the command's return value is being inverted using !.
               These are the same conditions obeyed by the errexit (-e) option.

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

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

          ulimit [-HSTabcdefilmnpqrstuvx [limit]]
               Provides control over the resources available to the shell and to
               processes started by it, on systems that allow such control.  The
               -H and -S options specify that the hard or soft limit is set for
               the given resource.  A hard limit cannot be increased by a non-
               root user once it is set; a soft limit may be increased up to the
               value of the hard limit.  If neither -H nor -S is specified, both
               the soft and hard limits are set.  The value of limit can be a
               number in the unit specified for the resource or one of the
               special values hard, soft, or unlimited, which stand for the
               current hard limit, the current soft limit, and no limit,
               respectively.  If limit is omitted, the current value of the soft
               limit of the resource is printed, unless the -H option is given.
               When more than one resource is specified, the limit name and unit
               are printed before the value.  Other options are interpreted as
               follows:
               -a   All current limits are reported
               -b   The maximum socket buffer size
               -c   The maximum size of core files created

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                                   2014 February 2

               -d   The maximum size of a process's data segment
               -e   The maximum scheduling priority ("nice")
               -f   The maximum size of files written by the shell and its
                    children
               -i   The maximum number of pending signals
               -l   The maximum size that may be locked into memory
               -m   The maximum resident set size (many systems do not honor
                    this limit)
               -n   The maximum number of open file descriptors (most systems do
                    not allow this value to be set)
               -p   The pipe size in 512-byte blocks (this may not be set)
               -q   The maximum number of bytes in POSIX message queues
               -r   The maximum real-time scheduling priority
               -s   The maximum stack size
               -t   The maximum amount of cpu time in seconds
               -u   The maximum number of processes available to a single user
               -v   The maximum amount of virtual memory available to the shell
                    and, on some systems, to its children
               -x   The maximum number of file locks
               -T   The maximum number of threads

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

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

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

          unset [-fv] [-n] [name ...]
               For each name, remove the corresponding variable or function.  If
               the -v option is given, each name refers to a shell variable, and
               that variable is removed.  Read-only variables may not be unset.
               If -f is specified, each name refers to a shell function, and the

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               function definition is removed.  If the -n option is supplied,
               and name is a variable with the nameref attribute, name will be
               unset rather than the variable it references.  -n has no effect
               if the -f option is supplied.  If no options are supplied, each
               name refers to a variable; if there is no variable by that name,
               any function with that name is unset.  Each unset variable or
               function is removed from the environment passed to subsequent
               commands.  If any of COMP_WORDBREAKS, RANDOM, SECONDS, LINENO,
               HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their
               special properties, even if they are subsequently reset.  The
               exit status is true unless a name is readonly.

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

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

          o    changing directories with cd

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

          o    specifying command names containing /

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

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

          o    importing function definitions from the shell environment at
               startup

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

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

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                                   2014 February 2

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

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

          o    using the enable builtin command to enable disabled shell
               builtins

          o    specifying the -p option to the command builtin command

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

          These restrictions are enforced after any startup files are read.

          When a command that is found to be a shell script is executed (see
          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
     IEEE --
          Portable Operating System Interface (POSIX) Part 2: Shell and Utilities,
               http://pubs.opengroup.org/onlinepubs/9699919799/
          http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
          sh(1), ksh(1), csh(1)
          emacs(1), vi(1)
          readline(3)

     FILES
          /bin/bash
               The bash executable
          /etc/profile
               The systemwide initialization file, executed for login shells
          ~/.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

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                                   2014 February 2

          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.

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