fortunes data file for Bash Shell
Version: 1.0
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Mt Xia Technical Consulting Group
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Specializing in Business Continuity, Disaster Recovery, AIX and HACMP

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Bash Shell - Definitions

These definitions are used throughout the remainder of this manual.

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Bash Shell - Definitions

  POSIX

A family of open system standards based on Unix. Bash is concerned with
POSIX  1003.2, the Shell and Tools Standard.

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Bash Shell - Definitions

  blank

A space or tab character.

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Bash Shell - Definitions

  builtin

A command that is implemented internally by the shell itself, rather
than by an  executable program somewhere in the file system.

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Bash Shell - Definitions

  control operator

A word that performs a control function. It is a newline or one of the
following:  `||', `&&', `&', `;', `;;', `|', `(', or `)'.

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Bash Shell - Definitions

  exit status

The value returned by a command to its caller. The value is restricted
to eight bits, so  the maximum value is 255.

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Bash Shell - Definitions

  field

A unit of text that is the result of one of the shell expansions. After
expansion, when  executing a command, the resulting fields are used as
the command name and  arguments.

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Bash Shell - Definitions

  filename

A string of characters used to identify a file.

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Bash Shell - Definitions

  job

A set of processes comprising a pipeline, and any processes descended
from it, that are  all in the same process group.

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Bash Shell - Definitions

  job control

A mechanism by which users can selectively stop (suspend) and restart
(resume)  execution of processes.

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Bash Shell - Definitions

  metacharacter

A character that, when unquoted, separates words. A metacharacter is a
blank or one  of the following characters: `|', `&', `;', `(', `)', `<',
or `>'.

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Bash Shell - Definitions

  name

A word consisting solely of letters, numbers, and underscores, and
beginning with a  letter or underscore. Names are used as shell variable
and function names. Also referred  to as an identifier.

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Bash Shell - Definitions

  operator

A control operator or a redirection operator.

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Bash Shell - Definitions

  process group

A collection of related processes each having the same process group ID.

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Bash Shell - Definitions

  process group ID

A unique identifer that represents a process group during its lifetime.

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Bash Shell - Definitions

  reserved word

A word that has a special meaning to the shell. Most reserved words
introduce shell  flow control constructs, such as for and while.

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Bash Shell - Definitions

  return status

A synonym for exit status.

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Bash Shell - Definitions

  signal

A mechanism by which a process may be notified by the kernel of an event
occurring in  the system.

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Bash Shell - Definitions

  special builtin

A shell builtin command that has been classified as special by the POSIX
1003.2  standard.

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Bash Shell - Definitions

  token

A sequence of characters considered a single unit by the shell. It is
either a word or an  operator.

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Bash Shell - Definitions

  word

A token that is not an operator.

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Bash Shell - Basic Shell Features

Bash is an acronym for `Bourne-Again SHell'. The Bourne shell is the
traditional Unix shell originally written by Stephen Bourne. All of the
Bourne shell builtin commands are  available in Bash, and the rules for
evaluation and quoting are taken from the POSIX 1003.2  specification
for the `standard' Unix shell.

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Bash Shell - Escape Character

A non-quoted backslash `\' is the Bash 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
itself is not quoted, the \newline is treated as a line continuation
(that is, it is  removed from the input stream and effectively ignored).

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Bash Shell - Single Quotes

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.

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Bash Shell - Double Quotes

Enclosing characters in double quotes (`"') preserves the literal value
of all characters within  the quotes, with the exception of `$', ``',
and `\'. The characters `$' 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. Within double quotes,
backslashes that are followed by one of these  characters are removed.
Backslashes preceding characters without a special meaning are left
unmodified. A double quote may be quoted within double quotes by
preceding it with a  backslash.

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Bash Shell - ANSI-C Quoting

Words of the form $'string' are treated specially. The word expands to
string, with  backslash-escaped characters replaced as specified by the
ANSI C standard. Backslash  escape sequences, if present, are decoded as
follows:

  \a - alert (bell)
  \b - backspace
  \e - an escape character (not ANSI C)
  \f - form feed
  \n - newline
  \r - carriage return
  \t - horizontal tab
  \v - vertical tab
  \\ - backslash
  \' - single 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)
  \cx - a control-x character

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

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Bash Shell - Locale-Specific Translation

A double-quoted string preceded by a dollar sign (`$') 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.

Some systems use the message catalog selected by the LC_MESSAGES shell
variable. Others  create the name of the message catalog from the value
of the TEXTDOMAIN shell variable,  possibly adding a suffix of `.mo'. If
you use the TEXTDOMAIN variable, you may need to set  the TEXTDOMAINDIR
variable to the location of the message catalog files. Still others use
both  variables in this fashion:

TEXTDOMAINDIR/LC_MESSAGES/LC_MESSAGES/TEXTDOMAIN.mo.

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Bash Shell - Simple Commands

A simple command is the kind of command encountered most often. It's
just a sequence of  words separated by blanks, terminated by one of the
shell's control operators. The first word
generally specifies a command to be executed, with the rest of the
words being that command's arguments.

The return status of a simple command is
its exit status as  provided by the POSIX 1003.1 waitpid function, or
128+n if the command was terminated  by signal n.

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Bash Shell - Pipelines

A pipeline is a sequence of simple commands separated by `|'.

The format for a pipeline is

  [time [-p]] [!] command1 [| command2 ...]

The output of each command in the pipeline is connected via a pipe to
the input of the next  command. That is, each command reads the previous
command's output.

The reserved word time causes timing statistics to be printed for the
pipeline once it finishes.

The statistics currently consist of elapsed (wall-clock) time and user
and system time consumed  by the command's execution. The `-p' option
changes the output format to that specified by  POSIX. The TIMEFORMAT
variable may be set to a format string that specifies how the timing
information should be displayed.  The use of time as a reserved word
permits the timing of shell builtins, shell  functions, and pipelines.
An external time command cannot time these easily.

If the pipeline is not executed asynchronously, the shell  waits for all
commands in the pipeline to complete.

Each command in a pipeline is executed in its own subshell. The exit
status of a pipeline is the exit status of the last command in the 
pipeline. If the reserved word `!' precedes the pipeline, the exit
status is the logical negation  of the exit status of the last command.

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Bash Shell - Lists of Commands

A list is a sequence of one or more pipelines separated by one of the
operators `;', `&',  `&&', or `||', and optionally terminated by one of
`;', `&', or a 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 to delimit
commands, equivalent to  a semicolon.

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Bash Shell - Lists of Commands

If a command is terminated by the control operator `&', the shell
executes the command  asynchronously in a subshell. This is known as
executing the command in the background. The  shell does not wait for
the command to finish, and the return status is 0 (true). When job
control  is not active, the standard input
for asynchronous commands, in the  absence of any explicit redirections,
is redirected from /dev/null.

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Bash Shell - Lists of Commands

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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Bash Shell - Lists of Commands

The control operators `&&' and `||' denote AND lists and OR lists,
respectively. 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.

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Bash Shell - Looping Constructs

  until

The syntax of the until command is:

  until test-commands; do consequent-commands; done

Execute consequent-commands as long as test-commands has an exit status
which is  not zero. The return status is the exit status of the last
command executed in  consequent-commands, or zero if none was executed.

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Bash Shell - Looping Constructs

  while

The syntax of the while command is:

  while test-commands; do consequent-commands; done

Execute consequent-commands as long as test-commands has an exit status
of zero.

The return status is the exit status of the last command executed in
consequent- commands, or zero if none was executed.

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Bash Shell - Looping Constructs

  for

The syntax of the for command is:

  for name [in words ...]; do commands; done

Expand words, and execute commands once for each member in the resultant
list, with  name bound to the current member. If `in words' is not
present, the for  command executes the commands once for each positional
parameter that is set, as if  `in "$@"' had been specified. The return 
status is the exit status of the last command that executes. If there
are no items in the  expansion of words, no commands are executed, and
the return status is zero.

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Bash Shell - Looping Constructs

An alternate form of the for command is also supported:

  for (( expr1 ; expr2 ; expr3 )) ; do commands ; done

First, the arithmetic expression expr1 is evaluated according to the
rules described  below. The
arithmetic expression expr2 is then  evaluated repeatedly until it
evaluates to zero. Each time expr2 evaluates to a non-zero  value,
commands are 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.

The break and continue builtins may be used to  control loop execution.

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Bash Shell - Conditional Constructs - if

The syntax of the if command is:

  if test-commands; then
    consequent-commands;
  [elif more-test-commands; then
    more-consequents;]
  [else alternate-consequents;]
  fi

The test-commands list is executed, and if its return status is zero,
the consequent- commands list is executed. If test-commands returns a
non-zero status, each elif list  is executed in turn, and if its exit
status is zero, the corresponding more-consequents is  executed and the
command completes. If `else alternate- consequents' is present, and the
final command in the final if or elif clause has  a non-zero exit
status, then alternate-consequents is executed. The return status is the
exit status of the last command executed, or zero if no condition tested
true.

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Bash Shell - Conditional Constructs - case

The syntax of the case command is:

  case word in [ [(] pattern [| pattern]...) command-list ;;]...
  esac

case will selectively execute the command-list corresponding to the
first pattern that  matches word. The `|' is used to separate multiple
patterns, and the `)' operator  terminates a pattern list. A list of
patterns and an associated command-list is known as a  clause. Each
clause must be terminated with `;;'. The word undergoes tilde
expansion, parameter expansion, command substitution, arithmetic
expansion, and  quote removal before matching is attempted. Each pattern
undergoes tilde expansion,  parameter expansion, command substitution,
and arithmetic expansion.

There may be an arbitrary number of case clauses, each terminated by a
`;;'. The  first pattern that matches determines the command-list that
is executed.

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Bash Shell - Conditional Constructs - case

Here is an example using case in a script that could be used to describe
one interesting  feature of an animal:

  echo -n "Enter the name of an animal: "
  read ANIMAL
  echo -n "The $ANIMAL has "
  case $ANIMAL in
    horse | dog | cat) echo -n "four";;
    man | kangaroo ) echo -n "two";;
    *) echo -n "an unknown number of";;
  esac
  echo " legs."

The return status is zero if no pattern is matched. Otherwise, the
return status is the exit  status of the command-list executed.

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Bash Shell - Conditional Constructs - select

The select construct allows the easy generation of menus. It has almost
the same  syntax as the for command:

  select name [in words ...]; do commands; 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 output
stream, each preceded by a  number. If the `in words' is omitted, the
positional parameters are printed, as if  `in "$@"' had been specifed.
The PS3 prompt is then displayed and a line is 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
select command  completes. Any other value read causes name to be set to
null. The line read is saved in  the variable REPLY.

The commands are executed after each selection until a break command is
executed,  at which point the select command completes.

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Bash Shell - Conditional Constructs - select

Here is an example that allows the user to pick a filename from the
current directory,  and displays the name and index of the file
selected.

  select fname in *;
  do
    echo you picked $fname \($REPLY\)
    break;
  done

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Bash Shell - Conditional Constructs - math

  (( expression ))

The arithmetic expression is evaluated according to the rules described
below. 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"

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Bash Shell - Conditional Expressions

  [[ expression ]]

Conditional Expressions. Word splitting and filename expansion are not
performed on  the words between the `[[' and `]]'; tilde expansion,
parameter and variable  expansion, arithmetic expansion, command
substitution, process substitution, and quote  removal are performed.

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Bash Shell - Conditional Expressions

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 in 3.5.8.1

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Bash Shell - Conditional Expressions - Pattern Matching

The return value is 0 if the string matches or does
not match the  pattern, respectively, and 1 otherwise. Any part of the
pattern may be quoted to force it  to be matched as a string.

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Bash Shell - Conditional Expressions

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.

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Bash Shell - Conditional Expressions

  ! expression

True if expression is false.

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Bash Shell - Conditional Expressions

  expression1 && expression2

True if both expression1 and expression2 are true.

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Bash Shell - Conditional Expressions

  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.

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Bash Shell - Grouping Commands

Bash provides two ways to group a list of commands to be executed as a
unit. When  commands are grouped, redirections may be applied to the
entire command list. For example,  the output of all the commands in the
list may be redirected to a single stream.

  ( list )

Placing a list of commands between parentheses causes a subshell to be
created, and  each of the commands in list to be executed in that
subshell. Since the list is executed in  a subshell, variable
assignments do not remain in effect after the subshell completes.

The exit status of this construct is the exit status of list.

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Bash Shell - Grouping Commands

  { list; }

Placing a list of commands between curly braces causes the list to be
executed in the  current shell context. No subshell is created. The
semicolon (or newline) following list is  required.

In addition to the creation of a subshell, there is a subtle difference
between these two  constructs due to historical reasons. The braces are
reserved words, so they must be  separated from the list by blanks. The
parentheses are operators, and are recognized as  separate tokens by the
shell even if they are not separated from the list by whitespace.

The exit status of this construct is the exit status of list.

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Bash Shell - Shell Functions

Shell functions are a way to group commands for later execution using a
single name for the group. They are executed just like a "regular"
command. 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. Shell functions are executed in the current shell context; no
new process is created to interpret them.

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Bash Shell - Shell Functions

Functions are declared using this syntax:

  [ function ] name () { command-list; }

This defines a shell 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 command-list between { and }.
This list is executed whenever name is specified as the name of a
command. The exit status of a function is the exit status of the last
command executed in the body.

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Bash Shell - Shell Functions

  [ function ] name () { command-list; }

Note that for historical reasons, the curly braces that surround the
body of the function must be separated from the body by blanks or
newlines. This is because the braces are reserved words and are only
recognized as such when they are separated by whitespace. Also, the
command- list must be terminated with a semicolon or a newline.

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Bash Shell - Shell Functions

When a function is executed, the arguments to the function become the
positional parameters during its execution. The special parameter `#'
that expands to the number of positional parameters is updated to
reflect the change. Positional parameter 0 is unchanged. The FUNCNAME
variable is set to the name of the function while the function is
executing.

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Bash Shell - Shell Functions

If the builtin command return is executed in a function, the function
completes and execution resumes with the next command after the function
call. 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. If a numeric argument is given to return,
that is the function's return status; otherwise the function's return
status is the exit status of the last command executed before the
return.

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Bash Shell - Shell Functions

Variables local to the function may be declared with the local builtin.
These variables are visible only to the function and the commands it
invokes.

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Bash Shell - Shell Functions

Functions may be recursive. No limit is placed on the number of
recursive calls.

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Bash Shell - 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 parameter N may be referenced as
${N}, or as $N when N consists of a single digit. Positional parameters
may not be assigned to with assignment statements. The set and shift
builtins are used to set and unset them. The positional parameters are
temporarily replaced when a shell function is executed.

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

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Bash Shell - Special Parameters

  *

Expands to the positional parameters, starting from one. When the
expansion occurs within double quotes, it expands to a single word with
the value of each parameter separated by the first character of the IFS
special variable. That is, "$*" is equivalent to "$1c$2c...", where c is
the first character of the value of the IFS variable. If IFS is unset,
the parameters are separated by spaces. If IFS is null, the parameters
are joined without intervening separators.

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Bash Shell - Special Parameters

  @

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" "$2" .... When there
are no positional parameters, "$@" and $@ expand to nothing (i.e., they
are removed).

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Bash Shell - Special Parameters

  #

Expands to the number of positional parameters in decimal.

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Bash Shell - Special Parameters

  ?

Expands to the exit status of the most recently executed foreground
pipeline. - (A hyphen.) 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).

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Bash Shell - Special Parameters

  $

Expands to the process ID of the shell. In a () subshell, it expands to
the process ID of the invoking shell, not the subshell.

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Bash Shell - Special Parameters

  !

Expands to the process ID of the most recently executed background
(asynchronous) command. 

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Bash Shell - Special Parameters

  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. 

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Bash Shell - Special Parameters

  _ 

(An underscore.) At shell startup, set to the absolute
filename of the shell or shell script being executed as passed in the
argument list. Subsequently, expands to the last argument to the
previous command, after expansion. Also set to the full pathname of each
command executed and placed in the environment exported to that command.

When checking mail, this parameter holds the name of the mail file.

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Bash Shell - Shell Expansions

Expansion is performed on the command line after it has been split into
tokens. There are seven kinds of expansion performed:

  * brace expansion
  * tilde expansion
  * parameter and variable expansion
  * command substitution
  * arithmetic expansion
  * word splitting
  * filename expansion

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Bash Shell - Brace Expansion

Brace expansion is a mechanism by which arbitrary strings may be
generated. This mechanism is similar to filename expansion, but the file
names generated need not exist. Patterns to be brace expanded take the
form of an optional preamble, followed by a series of comma-separated
strings 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.

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Bash Shell - Brace Expansion

Brace expansions may be nested. The results of each expanded string are
not sorted; left to right order is preserved. For example,

  $ echo a{d,c,b}e ade ace abe

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Bash Shell - Brace Expansion

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. To avoid
conflicts with parameter expansion, the string `${' is not considered
eligible for brace expansion.

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Bash Shell - Brace Expansion

A correctly-formed brace expansion must contain unquoted opening and
closing braces, and at least one unquoted comma. Any incorrectly formed
brace expansion is left unchanged.

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Bash Shell - 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}}

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Bash Shell - Tilde Expansion

If a word begins with an unquoted tilde character (`~'), all of the
characters up to 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 HOME shell variable. 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.

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Bash Shell - Tilde Expansion

If the tilde-prefix is `~+', the value of the shell variable PWD
replaces the tilde-prefix. If the tilde-prefix is `~-', the value of the
shell variable OLDPWD, if it is set, is substituted.

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Bash Shell - Tilde Expansion

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 characters
following tilde in the tilde-prefix as an argument. If the tilde-prefix,
sans the tilde, consists of a number without a leading `+' or `-', `+'
is assumed.

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

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Bash Shell - Tilde Expansion

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

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Bash Shell - Shell 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.

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Bash Shell - Shell Parameter Expansion

The basic form of parameter expansion is ${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 that is not to be interpreted as part of its
name.

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Bash Shell - Shell Parameter Expansion

If the first character of a parameter is an exclamation point, a level of
variable indirection is introduced. Bash uses the value of the variable
formed from the rest of parameter as the name of the variable; this
variable is then expanded and that value is used in the rest of the
substitution, rather than the value of parameter itself. This is known
as indirect expansion. The exception to this is the expansion of
${!prefix*} described below.

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Bash Shell - Shell Parameter Expansion

When not performing substring expansion, Bash tests for a parameter that
is unset or null; omitting the colon results in a test only for a
parameter that is unset. Put another way, if the colon is included, the
operator tests for both existence and that the value is not null; if the
colon is omitted, the operator tests only for existence.

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Bash Shell - Shell Parameter Expansion

  ${parameter:-word}

If parameter is unset or null, the expansion of word is substituted.
Otherwise, the value of parameter is substituted.

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Bash Shell - Shell Parameter Expansion

  ${parameter:=word}

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.

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Bash Shell - Shell Parameter Expansion

  ${parameter:?word}

If parameter is null or unset, the expansion of word (or a message to
that effect if word is not present) is written to the standard error and
the shell, if it is not interactive, exits.

Otherwise, the value of parameter is substituted.

%
Bash Shell - Shell Parameter Expansion

  ${parameter:+word}

If parameter is null or unset, nothing is substituted, otherwise the
expansion of word is substituted.

%
Bash Shell - Shell Parameter Expansion

  ${parameter:offset}
  ${parameter:offset:length}

Expands to up to length characters of parameter starting at the
character specified by offset. If length is omitted, expands to the
substring of parameter starting at the character specified by offset.
length and offset are arithmetic expressions. This is referred to as
Substring Expansion. length must evaluate to a number greater than or
equal to zero. If offset evaluates to a number less than zero, the value
is used as an offset from the end of the value of parameter. If
parameter is `@', the result is length positional parameters beginning
at offset. If parameter is an array name indexed by `@' or `*', the
result is the length members of the array beginning with
${parameter[offset]}. Substring indexing is zero-based unless the
positional parameters are used, in which case the indexing starts at 1.

%
Bash Shell - Shell Parameter Expansion

  ${!prefix*}

Expands to the names of variables whose names begin with prefix,
separated by the first character of the IFS special variable.

%
Bash Shell - Shell Parameter Expansion

  ${#parameter}

The length in characters of the expanded 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.

%
Bash Shell - Shell Parameter Expansion

  ${parameter#word}
  ${parameter##word}

The word is expanded to produce a pattern just as in filename expansion.
If the pattern matches the beginning 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.

%
Bash Shell - Shell Parameter Expansion

  ${parameter%word}
  ${parameter%%word}

The word is expanded to produce a pattern just as in filename expansion.
If the pattern matches a trailing portion of the expanded value of
parameter, then the result of the expansion is the 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.

%
Bash Shell - Shell Parameter Expansion

  ${parameter/pattern/string}
  ${parameter//pattern/string}

The pattern is expanded to produce a pattern just as in filename
expansion. Parameter is expanded and the longest match of pattern
against its value is replaced with string.

In the first form, only the first match is replaced. The second form
causes all matches of pattern to be replaced with string. 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.

%
Bash Shell - Command Substitution

Command substitution allows the output of a command to replace the
command itself.

Command substitution occurs when a command is enclosed as follows:

    $(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).

%
Bash Shell - Command Substitution

When the old-style backquote form of command 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.

%
Bash Shell - Command Substitution

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 filename expansion are
not performed on the results.

%
Bash Shell - 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 expansion, command substitution, and
quote removal. Arithmetic substitutions may be nested. If the expression
is invalid, Bash prints a message indicating failure to the standard
error and no substitution occurs.

%
Bash Shell - 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. Note that no space may appear between the <
or > and the left parenthesis, otherwise the construct would be
interpreted as a redirection.

%
Bash Shell - Process Substitution

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

%
Bash Shell - 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.

%
Bash Shell - Word Splitting

The shell treats each character of $IFS as a delimiter, and splits the
results of the other expansions into words on these characters. If IFS
is unset, or its value is exactly , the default,
then any sequence of IFS characters 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.

%
Bash Shell - Word Splitting

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.

%
Bash Shell - Filename Expansion

Bash scans each word for the characters `*', `?', and `['. If one of
these characters appears, then the word is regarded as a pattern, and
replaced with an alphabetically sorted list of file names matching the
pattern. If no matching file names are found, and the shell option
nullglob is disabled, the word is left unchanged. If the nullglob option
is set, and no matches are found, the word is removed. If the shell
option nocaseglob is enabled, the match is performed without regard to
the case of alphabetic characters.

%
Bash Shell - Filename Expansion

When a pattern is used for filename generation, the character `.' at the
start of a filename or immediately following a slash must be matched
explicitly, unless the shell option dotglob is set.

%
Bash Shell - Filename Expansion

The GLOBIGNORE shell variable may be used to restrict the set of
filenames matching a pattern.

%
Bash Shell - Filename Expansion

If GLOBIGNORE is set, each matching filename that also matches one of
the patterns in

%
Bash Shell - Filename Expansion

GLOBIGNORE is removed from the list of matches. The filenames `.' and
`..' are always ignored, even when GLOBIGNORE is set. However, setting
GLOBIGNORE 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.

%
Bash Shell - 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. The special pattern characters must be quoted if
they are to be matched literally.

%
Bash Shell - Pattern Matching

  *

Matches any string, including the null string.

%
Bash Shell - Pattern Matching

  ?

Matches any single character.

%
Bash Shell - Pattern Matching

  [...]

Matches any one of the enclosed characters. A pair of characters
separated by a hyphen denotes a range expression; any character that
sorts between those two characters, inclusive, using the current
locale's collating sequence and character set, is matched. If the first
character following the `[' is a `!' or a `^' then any character not
enclosed is matched. 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. The sorting order of characters in range
expressions is determined by the current locale and the value of the
LC_COLLATE shell variable, if set.

%
Bash Shell - Pattern Matching

In the default C locale, `[a-dx-z]' is equivalent to
`[abcdxyz]'. Many locales sort characters in dictionary order, and in
these locales `[a-dx-z]' is typically not equivalent to `[abcdxyz]'; it
might be equivalent to `[aBbCcDdxXyYz]', for example. To obtain the
traditional interpretation of ranges in bracket expressions, you can
force the use of the C locale by setting the LC_COLLATE or LC_ALL
environment variable to the value `C'.

%
Bash Shell - Pattern Matching

Within `[' and `]', character classes can be specified using the syntax
[:class:], where class is one of the following classes defined in the
POSIX 1003.2 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 `_'.

%
Bash Shell - Pattern Matching

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

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

%
Bash Shell - Pattern Matching

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 `|'. 

%
Bash Shell - Pattern Matching

  ?(pattern-list)

Matches zero or one occurrence of the given patterns.

%
Bash Shell - Pattern Matching

  *(pattern-list)

Matches zero or more occurrences of the given patterns.

%
Bash Shell - Pattern Matching

  +(pattern-list)

Matches one or more occurrences of the given patterns.

%
Bash Shell - Pattern Matching

  @(pattern-list)

Matches exactly one of the given patterns.

%
Bash Shell - Pattern Matching

  !(pattern-list)

Matches anything except one of the given patterns.

%
Bash Shell - 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.

%
Bash Shell - Redirections

  ls > dirlist 2>&1

directs both standard output (file descriptor 1) and standard error
(file descriptor 2) to the file dirlist, while the command

%
Bash Shell - Redirections

  ls 2>&1 > dirlist

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

%
Bash Shell - Redirections

  /dev/fd/fd

If fd is a valid integer, file descriptor fd is duplicated. 

%
Bash Shell - Redirections

  /dev/stdin

File descriptor 0 is duplicated.

%
Bash Shell - Redirections

  /dev/stdout

File descriptor 1 is duplicated.

%
Bash Shell - Redirections

  /dev/stderr

File descriptor 2 is duplicated.

%
Bash Shell - Redirections

  /dev/tcp/host/port

If host is a valid hostname or Internet address, and port is an integer
port number or service name, Bash attempts to open a TCP connection to
the corresponding socket.

%
Bash Shell - Redirections

  /dev/udp/host/port

If host is a valid hostname or Internet address, and port is an integer
port number or service name, Bash attempts to open a UDP connection to
the corresponding socket.

%
Bash Shell - Redirecting Input

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

The general format for redirecting input is:

  [n][|]word

%
Bash Shell - Redirecting Output

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 is not enabled, the redirection is attempted even
if the file named by word exists.

%
Bash Shell - 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

%
Bash Shell - Redirecting Standard Output and Standard Error

Bash 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 with this construct. 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

%
Bash Shell - Here Documents

This type of redirection instructs the shell to read input from the
current source until a line containing only word (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

%
Bash Shell - Here Documents

  <<[-]word
  here-document
  delimiter

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

%
Bash Shell - Here Documents

  <<[-]word
  here-document
  delimiter

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.

%
Bash Shell - Here Strings

A variant of here documents, the format is:

  <<&word

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

%
Bash Shell - 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.

%
Bash Shell - Moving File Descriptors

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.

%
Bash Shell - 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.

%
Bash Shell - Simple Command Expansion

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

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

Step 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.

Step 3. Redirections are performed as described above.

Step 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.

%
Bash Shell - Command Search and Execution

After a command has been split into words, if it results in a simple
command and an optional list of arguments, the 6 steps are
taken. 

Step 1. 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 in 3.3 Shell Functions.

%
Bash Shell - Command Search and Execution

Step 2. If the name does not match a function, the shell searches for it in
the list of shell builtins.

%
Bash Shell - Command Search and Execution

If a match is found, that builtin is invoked.

Step 3. If the name is neither a shell function nor a builtin, and
contains no slashes, Bash searches each element of $PATH for a directory
containing an executable file by that name. Bash uses a hash table to
remember the full pathnames of executable files to avoid multiple PATH
searches.

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 prints an error message and returns an exit status of 127.

%
Bash Shell - Command Search and Execution

Step 4. 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 supplied, if
any.

%
Bash Shell - Command Search and Execution

Step 5. 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 and
the shell executes it as described in 3.8 Shell Scripts.

%
Bash Shell - Command Search and Execution

Step 6. If the command was not begun asynchronously, the shell waits for the
command to complete and collects its exit status.

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

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

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

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

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

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

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

  * current traps set by trap

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

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

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

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

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

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

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

  * options enabled by shopt

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

  * shell aliases defined with alias

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

  * 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.

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

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

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

  * the current working directory

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

  * the file creation mode mask

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

  * shell variables marked for export, along with variables exported for
    the command, passed in the environment

%
Bash Shell - Command Execution Environment

The shell has an execution environment, one component of which is the
following:

  * 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.

%
Bash Shell - Command Execution Environment

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

%
Bash Shell - Command Execution Environment

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.

%
Bash Shell - 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.

%
Bash Shell - Environment

Bash 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 and `export -n' commands, plus any
additions via the export and `declare -x' commands.

%
Bash Shell - Environment

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

%
Bash Shell - Environment

If the `-k' option is set, then all parameter assignments are placed in
the environment for a command, not just those that precede the command
name.

%
Bash Shell - Environment

When Bash invokes an external command, the variable `$_' is set to the
full path name of the command and passed to that command in its
environment.

%
Bash Shell - Exit Status

For the shell's purposes, a command which exits with a zero exit status
has succeeded. A non- zero exit status indicates failure. This seemingly
counter-intuitive scheme is used so there is one well-defined way to
indicate success and a variety of ways to indicate various failure
modes.

%
Bash Shell - Exit Status

When a command terminates on a fatal signal whose number is N, Bash uses
the value 128+N as the exit status.

%
Bash Shell - 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.

%
Bash Shell - Exit Status

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

%
Bash Shell - Exit Status

The exit status is used by the Bash conditional commands and some of the
list constructs.

%
Bash Shell - Exit Status

All of the Bash builtins return an exit status of zero if they succeed
and a non-zero status on failure, so they may be used by the conditional
and list constructs. All builtins return an exit status of 2 to indicate
incorrect usage.

%
Bash Shell - 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). When Bash receives a SIGINT, it breaks out of any
executing loops. In all cases, Bash ignores SIGQUIT. If job control is
in effect, Bash ignores SIGTTIN, SIGTTOU, and SIGTSTP.

%
Bash Shell - Signals

Commands started 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 as well.
Commands run as a result of command substitution ignore the keyboard-
generated job control signals SIGTTIN, SIGTTOU, and SIGTSTP.

%
Bash Shell - Signals

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 SIGHUP signal to a particular job, it
should be removed from the jobs table with the disown builtin or marked
to not receive SIGHUP using disown -h.

%
Bash Shell - Signals

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

%
Bash Shell - Signals

When Bash receives a signal for which a trap has been set while waiting
for a command to complete, 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.

%
Bash Shell - Shell Scripts

A shell script is a text file containing shell commands. When such a
file is used as the first non- option argument when invoking Bash, and
neither the `-c' nor `-s' option is supplied, Bash reads and executes
commands from the file, then exits. This mode of operation creates a
non-interactive shell. The shell first searches for the file in the
current directory, and looks in the directories in $PATH if not found
there.

%
Bash Shell - Shell Scripts

When Bash runs a shell script, it sets the special parameter 0 to the
name of the file, rather than the name of the shell, and the positional
parameters are set to the remaining arguments, if any are given. If no
additional arguments are supplied, the positional parameters are unset.

%
Bash Shell - Shell Scripts

A shell script may be made executable by using the chmod command to turn
on the execute bit.

%
Bash Shell - Shell Scripts

When Bash finds such a file while searching the $PATH for a command, it
spawns a subshell to execute it. In other words, executing filename
arguments is equivalent to executing bash filename arguments if filename
is an executable shell script. This subshell reinitializes itself, so
that the effect is as if a new shell had been invoked to interpret the
script, with the exception that the locations of commands remembered by
the parent are retained by the child.

%
Bash Shell - Shell Scripts

Most versions of Unix make this a part of the operating system's command
execution mechanism. If the first line of a script begins with the two
characters `#!', the remainder of the line specifies an interpreter for
the program. Thus, you can specify Bash, awk, Perl, or some other
interpreter and write the rest of the script file in that language.

%
Bash Shell - Shell Scripts

The arguments to the interpreter consist of a single optional argument
following the interpreter name on the first line of the script file,
followed by the name of the script file, followed by the rest of the
arguments. Bash will perform this action on operating systems that do
not handle it themselves. Note that some older versions of Unix limit
the interpreter name and argument to a maximum of 32 characters.

%
Bash Shell - Shell Scripts

Bash scripts often begin with #! /bin/bash (assuming that Bash has been
installed in `/bin'), since this ensures that Bash will be used to
interpret the script, even if it is executed under another shell.

%
Bash Shell - Bourne Shell Builtins

The following shell builtin commands are inherited from the Bourne
Shell. These commands are implemented as specified by the POSIX 1003.2
standard. 

  : (a colon)
  : [arguments]

Do nothing beyond expanding arguments and performing redirections. The return
status is zero.

%
Bash Shell - Bourne Shell Builtins

  . (a period)
  . filename [arguments]

Read and execute commands from the filename argument in the current
shell context. If filename does not contain a slash, the PATH variable
is used to find filename. When Bash is not in POSIX mode, the current
directory is searched if filename is not found in $PATH. 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 exit status of the last command executed, or
zero if no commands are executed. If filename is not found, or cannot be
read, the return status is non-zero. This builtin is equivalent to
source. 

%
Bash Shell - Bourne Shell Builtins

  break
  break [n]

Exit from a for, while, until, or select loop. If n is supplied, the nth
enclosing loop is exited. n must be greater than or equal to 1. The
return status is zero unless n is not greater than or equal to 1.

%
Bash Shell - Bourne Shell Builtins

  cd
  cd [-L|-P] [directory]

Change the current working directory to directory. If directory is not
given, the value of the HOME shell variable is used. If the shell
variable CDPATH exists, it is used as a search path. If directory begins
with a slash, CDPATH is not used. The `-P' option means to not follow
symbolic links; symbolic links are followed by default or with the `-L'
option. If directory is `-', it is equivalent to $OLDPWD. The return
status is zero if the directory is successfully changed, non-zero
otherwise.

%
Bash Shell - Bourne Shell Builtins

  continue
  continue [n]

Resume the next iteration of an enclosing for, while, until, or select
loop. If n is supplied, the execution of the nth enclosing loop is
resumed. n must be greater than or equal to 1. The return status is zero
unless n is not greater than or equal to 1.

%
Bash Shell - Bourne Shell Builtins

  eval
  eval [arguments]

The arguments are concatenated together into a single command, which is
then read and executed, and its exit status returned as the exit status
of eval. If there are no arguments or only empty arguments, the return
status is zero.

%
Bash Shell - Bourne Shell Builtins

  exec
  exec [-cl] [-aname] [command [arguments] ]

If command is supplied, it replaces the shell without creating a new
process. If the `- l' option is supplied, the shell places a dash at the
beginning of the zeroth arg passed to command. This is what the login
program 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 command. If no command is specified, redirections may
be used to affect the current shell environment. If there are no
redirection errors, the return status is zero; otherwise the return
status is non-zero.

%
Bash Shell - Bourne Shell Builtins

  exit
  exit [n]

Exit the shell, returning a status of n to the shell's parent. If n is
omitted, the exit status is that of the last command executed. Any trap
on EXIT is executed before the shell terminates.

%
Bash Shell - Bourne Shell Builtins

  export
  export [-fn] [-p] [name[=value] ]

Mark each name to be passed to child processes in the environment. If
the `-f' option is supplied, the names refer to shell functions;
otherwise the names refer to shell variables. The `-n' option means to
no longer mark each name for export. If no names are supplied, or if the
`-p' option is given, a list of exported names is displayed. The `-p'
option displays output in a form that may be reused as input. The return
status is zero unless an invalid option is supplied, one of the names is
not a valid shell variable name, or `-f' is supplied with a name that is
not a shell function.

%
Bash Shell - Bourne Shell Builtins

  getopts
  getopts optstring name [args]

getopts is used by shell scripts 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 (`?') 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.

%
Bash Shell - Bourne Shell Builtins - getopts

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.

%
Bash Shell - Bourne Shell Builtins - getopts

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.

%
Bash Shell - Bourne Shell Builtins - getopts

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.

%
Bash Shell - Bourne Shell Builtins

  hash
  hash [-'r] [-p filename] [-dt] [name]

Remember the full pathnames of commands specified as name arguments, so
they need not be searched for on subsequent invocations. The commands
are found by searching through the directories listed in $PATH. The `-p'
option inhibits the path search, and filename is used as the location of
name. 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 zero unless a name is not found or an invalid option is
supplied.

%
Bash Shell - Bourne Shell Builtins

  pwd
  pwd [-LP]

Print the absolute pathname of the current working directory. If the
`-P' option is supplied, the pathname printed will not contain symbolic
links. If the `-L' option is supplied, the pathname printed may contain
symbolic links. The return status is zero unless an error is encountered
while determining the name of the current directory or an invalid option
is supplied.

%
Bash Shell - Bourne Shell Builtins

  readonly
  readonly [-apf] [name] ...

Mark each name as readonly. The values of these names may not be changed
by subsequent assignment. If the `-f' option is supplied, each name
refers to a shell function. The `-a' option means each name refers to an
array variable. If no name arguments are given, or if the `-p' option is
supplied, a list of all readonly names is printed. The `-p' option
causes output to be displayed in a format that may be reused as input.
The return status is zero unless an invalid option is supplied, one of
the name arguments is not a valid shell variable or function name, or
the `-f' option is supplied with a name that is not a shell
function.

%
Bash Shell - Bourne Shell Builtins

  return
  return [n]

Cause a shell function to exit with the return value n. If n is not
supplied, the return value is the exit status of the last command
executed in the function. This may also be used to terminate execution
of a script being executed with the . (or source) builtin, returning
either n or the exit status of the last command executed within the
script as the exit status of the script. The return status is non-zero
if return is used outside a function and not during the execution of a
script by . or source.

%
Bash Shell - Bourne Shell Builtins

  shift
  shift [n]

Shift the positional parameters to the left by n. The positional
parameters from n+1 ... $# are renamed to $1 ... $#-n+1. Parameters
represented by the numbers $# to n+1 are unset. n must be a non-negative
number less than or equal to $#. If n is zero or greater than $#, the
positional parameters are not changed. If n is not supplied, it is
assumed to be 1. The return status is zero unless n is greater than $#
or less than zero, non-zero otherwise.

%
Bash Shell - Bourne Shell Builtins

  test
  [

Evaluate a conditional expression expr. Each operator and operand must
be a separate argument. Expressions are composed of the primaries
described below in 6.4 Bash Conditional Expressions.

When the [ form is used, the last argument to the command must be a ].

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

%
Bash Shell - Bourne Shell Builtins

  ! expr

True if expr is false.

%
Bash Shell - Bourne Shell Builtins

  ( expr )

Returns the value of expr. This may be used to override the normal
precedence of operators.

%
Bash Shell - Bourne Shell Builtins

  expr1 -a expr2

True if both expr1 and expr2 are true.

%
Bash Shell - Bourne Shell Builtins

  expr1 -o expr2

True if either expr1 or expr2 is true.

%
Bash Shell - Bourne Shell Builtins - test

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

  0 arguments

The expression is false.

%
Bash Shell - Bourne Shell Builtins - test

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

  1 argument

The expression is true if and only if the argument is not null.

%
Bash Shell - Bourne Shell Builtins - test

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

  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, the expression is true if the unary test is true.
If the first argument is not a valid unary operator, the expression is
false.

%
Bash Shell - Bourne Shell Builtins - test

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

  3 arguments

If the second argument is one of the binary conditional operators, the
result of the expression is the result of the binary test using the
first and third arguments as operands. 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. The `-a' and `-o'
operators are considered binary operators in this case. 

%
Bash Shell - Bourne Shell Builtins - test

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

  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.

%
Bash Shell - Bourne Shell Builtins - test

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

  5 or more arguments

The expression is parsed and evaluated according to precedence using the
rules listed above. 

%
Bash Shell - Bourne Shell Builtins

  times
  times

Print out the user and system times used by the shell and its children.
The return status is zero.

%
Bash Shell - Bourne Shell Builtins - trap

  trap
  trap [-lp] [arg] [sigspec...]

The commands in arg are to be read and executed when the shell receives
signal sigspec. If arg is absent or equal to `-', all specified signals
are reset to the values they had when the shell was started. If arg is
the null string, then the signal specified by each sigspec is ignored by
the shell and commands it invokes. If arg is not present and `-p' has
been supplied, the shell displays the trap commands associated with each
sigspec. If no arguments are supplied, or only `-p' is given, trap
prints the list of commands associated with each signal number in a form
that may be reused as shell input. Each sigspec is either a signal name
such as SIGINT (with or without the SIG prefix) or a signal number. If a
sigspec is 0 or EXIT, arg is executed when the shell exits. If a sigspec
is DEBUG, the command arg is executed after every simple command.

%
Bash Shell - Bourne Shell Builtins - trap

  trap
  trap [-lp] [arg] [sigspec...]
If a sigspec is ERR, the command arg is executed whenever a simple
command has a non-zero exit status. The ERR trap is not executed if the
failed command is part of an until or while loop, part of an if
statement, part of a && or || list, or if the command's return status is
being inverted using !. The `-l' option causes the shell to print a list
of signal names and their corresponding numbers.

%
Bash Shell - Bourne Shell Builtins - trap

  trap
  trap [-lp] [arg] [sigspec...]

Signals ignored upon entry to the shell cannot be trapped or reset.
Trapped signals are reset to their original values in a child process
when it is created.

%
Bash Shell - Bourne Shell Builtins - trap

  trap
  trap [-lp] [arg] [sigspec...]

The return status is zero unless a sigspec does not specify a valid
signal.

%
Bash Shell - Bourne Shell Builtins - umask

  umask
  umask [-p] [-S] [mode]

Set the shell process's file creation mask to mode. If mode begins with
a digit, it is interpreted as an octal number; if not, it is interpreted
as a symbolic mode mask similar to that accepted by the chmod command.
If mode is omitted, the current value of the mask is printed. If the
`-S' option is supplied without a mode argument, the mask is printed in
a symbolic format. 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 zero if the mode is successfully changed or if no mode argument is
supplied, and non-zero otherwise.

%
Bash Shell - Bourne Shell Builtins - umask

  umask
  umask [-p] [-S] [mode]

Note that when the mode is interpreted as an octal number, each number
of the umask is subtracted from 7. Thus, a umask of 022 results in
permissions of 755.

%
Bash Shell - Bourne Shell Builtins

  unset
  unset [-fv] [name]

Each variable or function name is removed. If no options are supplied,
or the `-v' option is given, each name refers to a shell variable. If
the `-f' option is given, the names refer to shell functions, and the
function definition is removed. Readonly variables and functions may not
be unset. The return status is zero unless a name does not exist or is
readonly.

%
Bash Shell - Bash Builtin Commands

  alias
  alias [-p] [name[=value]...]

Without arguments or with the `-p' option, alias prints the list of
aliases on the standard output in a form that allows them to be reused
as input. If arguments are supplied, an alias is defined for each name
whose value is given. If no value is given, the name and value of the
alias is printed. Aliases are described in 6.6 Aliases. 

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

Display current Readline key and function bindings, bind a key sequence
to a Readline function or macro, or set a Readline variable. Each
non-option argument is a command as it would appear in a a Readline
initialization file, 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:

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-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.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-l

List the names of all Readline functions.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-p

Display Readline function names and bindings in such a way that they can
be used as input or in a Readline initialization file. 

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-P

List current Readline function names and bindings.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-v

Display Readline variable names and values in such a way that they can
be used as input or in a Readline initialization file.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-V

List current Readline variable names and values.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-s

Display Readline key sequences bound to macros and the strings they
output in such a way that they can be used as input or in a Readline
initialization file.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-S

Display Readline key sequences bound to macros and the strings they
output.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-f filename

Read key bindings from filename.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-q function

Query about which keys invoke the named function.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-u function

Unbind all keys bound to the named function.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-r keyseq

Remove any current binding for keyseq.

%
Bash Shell - Bash Builtin Commands - bind

  bind [-m keymap] [-lpsvPSV]
  bind [-m keymap] [-q function] [-u function] [-r keyseq]
  bind [-m keymap] -f filename
  bind [-m keymap] -x keyseq:shell-command
  bind [-m keymap] keyseq:function-name
  bind readline-command

-x keyseq:shell-command

Cause shell-command to be executed whenever keyseq is entered.

%
Bash Shell - Bash Builtin Commands

builtin [shell-builtin [args]]

Run a shell builtin, passing it args, and return its exit status. This
is useful when defining a shell function with the same name as a shell
builtin, retaining the functionality of the builtin within the function.
The return status is non-zero if shell-builtin is not a shell builtin
command. 

%
Bash Shell - Bash Builtin Commands

  command
  command [-pVv]command [arguments...]

Runs command with arguments ignoring any shell function named command.
Only shell builtin commands or commands found by searching the PATH are
executed. If there is a shell function named ls, running `command ls'
within the function will execute the external command ls instead of
calling the function recursively. The `-p' option means to use a default
value for PATH that is guaranteed to find all of the standard utilities.
The return status in this case is 127 if command cannot be found or an
error occurred, and the exit status of command otherwise.

%
Bash Shell - Bash Builtin Commands

  command
  command [-pVv]command [arguments...]

If either the `-V' or `-v' option is supplied, a description of command
is printed.

%
Bash Shell - Bash Builtin Commands

  command
  command [-pVv]command [arguments...]

The `-v' option causes a single word indicating the command or file name
used to invoke command to be displayed; the `-V' option produces a more
verbose description. In this case, the return status is zero if command
is found, and non-zero if not.

%
Bash Shell - Bash Builtin Commands - declare

  declare
  declare [-afFirtx] [-p] [name[=value]]

Declare variables and give them attributes. If no names are given, then
display the values of variables instead.

The `-p' option will display the attributes and values of each name.
When `-p' is used, additional options are ignored. The `-F' option
inhibits the display of function definitions; only the function name and
attributes are printed. `-F' implies `-f'. The following options can be
used to restrict output to variables with the specified attributes or to
give variables attributes:

%
Bash Shell - Bash Builtin Commands - declare

  declare
  declare [-afFirtx] [-p] [name[=value]]

-a

Each name is an array variable.

%
Bash Shell - Bash Builtin Commands - declare

  declare
  declare [-afFirtx] [-p] [name[=value]]

-f

Use function names only.

%
Bash Shell - Bash Builtin Commands - declare

  declare
  declare [-afFirtx] [-p] [name[=value]]

-i

The variable is to be treated as an integer; arithmetic evaluation is
performed when the variable is assigned a value.

%
Bash Shell - Bash Builtin Commands - declare

  declare
  declare [-afFirtx] [-p] [name[=value]]

-r

Make names readonly. These names cannot then be assigned values by
subsequent assignment statements or unset.

%
Bash Shell - Bash Builtin Commands - declare

  declare
  declare [-afFirtx] [-p] [name[=value]]

-t

Give each name the trace attribute. Traced functions inherit the DEBUG
trap from the calling shell. The trace attribute has no special meaning
for variables.

%
Bash Shell - Bash Builtin Commands - declare

  declare
  declare [-afFirtx] [-p] [name[=value]]

-x

Mark each name for export to subsequent commands via the environment.

%
Bash Shell - Bash Builtin Commands - declare

  declare
  declare [-afFirtx] [-p] [name[=value]]

The return status is zero 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, 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'.

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

Output the args, separated by spaces, terminated with a newline. The
return status is always 0. If `-n' is specified, the trailing newline is
suppressed. If the `-e' option is given, interpretation of the following
backslash-escaped characters is enabled. The `- E' option disables the
interpretation of these escape characters, even on systems where they
are interpreted by default. The xpg_echo shell option may be used to
dynamically determine whether or not echo expands these escape
characters by default. echo interprets the following escape sequences:

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\a 

alert (bell) 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\b 

backspace 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\c 

suppress trailing newline 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\e 

escape 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\f 

form feed 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\n 

new line 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\r 

carriage return 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\t 

horizontal tab 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\v 

vertical tab 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\\ 

backslash 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\0nnn 

the eight-bit character whose value is the octal value nnn (zero to
three octal digits) 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\nnn 

the eight-bit character whose value is the octal value nnn (one to three
octal digits) 

%
Bash Shell - Bash Builtin Commands - echo

  echo
  echo [-neE] [arg...]

\xHH 

the eight-bit character whose value is the hexadecimal value HH (one or
two hex digits)  enable 
 
%
Bash Shell - Bash Builtin Commands - enable

  enable [-n] [-p] [-f filename] [-ads] [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, the names
become disabled. Otherwise names are enabled. For example, to use the
test binary found via $PATH instead of the shell builtin version, type
`enable -n test'.

%
Bash Shell - Bash Builtin Commands - enable

  enable [-n] [-p] [-f filename] [-ads] [name ...]

If the `-p' option is supplied, or no name arguments appear, a list of
shell builtins is printed. With no other arguments, the list consists of
all enabled shell builtins. The `- a' option means to list each builtin
with an indication of whether or not it is enabled.

%
Bash Shell - Bash Builtin Commands - enable

  enable [-n] [-p] [-f filename] [-ads] [name ...]

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 loaded with `-f'.

%
Bash Shell - Bash Builtin Commands - enable

  enable [-n] [-p] [-f filename] [-ads] [name ...]

If there are no options, a list of the shell builtins is displayed. The
`-s' option restricts enable to the POSIX special builtins. If `-s' is
used with `-f', the new builtin becomes a special builtin.

%
Bash Shell - Bash Builtin Commands - enable

  enable [-n] [-p] [-f filename] [-ads] [name ...]

The return status is zero unless a name is not a shell builtin or there
is an error loading a new builtin from a shared object. 

%
Bash Shell - Bash Builtin Commands - help

  help
  help [-s] [pattern]

Display helpful information about builtin commands. If pattern is
specified, help gives detailed help on all commands matching pattern,
otherwise a list of the builtins is printed. The `-s' option restricts
the information displayed to a short usage synopsis.

The return status is zero unless no command matches pattern.

%
Bash Shell - Bash Builtin Commands

  let expression [expression]

The let builtin allows arithmetic to be performed on shell variables.
Each expression is evaluated according to the rules given below in 6.5
Shell Arithmetic. If the last expression evaluates to 0, let returns 1;
otherwise 0 is returned. local

%
Bash Shell - Bash Builtin Commands

  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. local
can only be used within a function; it makes the variable name have a
visible scope restricted to that function and its children. The return
status is zero unless local is used outside a function, an invalid name
is supplied, or name is a readonly variable. 

%
Bash Shell - Bash Builtin Commands

  logout
  logout [n]

Exit a login shell, returning a status of n to the shell's parent.

%
Bash Shell - Bash Builtin Commands

  printf
  printf format [arguments]

Write the formatted arguments to the standard output under the control
of the format.

%
Bash Shell - Bash Builtin Commands

  printf
  printf format [arguments]

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) formats, `%b'
causes printf to expand backslash escape sequences in the corresponding
argument, and `%q' causes printf to output the corresponding argument in
a format that can be reused as shell input.

%
Bash Shell - Bash Builtin Commands

  printf
  printf format [arguments]

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.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

One line is read from the standard input, or from the file descriptor fd
supplied as an argument to the `-u' option, and the first word is
assigned to the first name, the second word to the second name, and so
on, with leftover words and their intervening separators assigned to the
last name. If there are fewer words read from the input stream than
names, the remaining names are assigned empty values. The characters in
the value of the IFS variable are used to split the line into words. The
backslash character `\' may be used to remove any special meaning for
the next character read and for line continuation. 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, or an
invalid file descriptor is supplied as the argument to `-u'.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-a aname

The words are assigned to sequential indices of the array variable
aname, starting at 0.

All elements are removed from aname before the assignment. Other name
arguments are ignored.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-d delim

The first character of delim is used to terminate the input line, rather
than newline.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-e

Readline is used to obtain the line.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-n nchars

read returns after reading nchars characters rather than waiting for a
complete line of input.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-p prompt

Display prompt, without a trailing newline, before attempting to read
any input. The prompt is displayed only if input is coming from a
terminal.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-r

If this option is given, 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.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-s

Silent mode. If input is coming from a terminal, characters are not
echoed.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-t timeout

Cause read to time out and return failure if a complete line of input is
not read within timeout seconds. This option has no effect if read is
not reading input from the terminal or a pipe.

%
Bash Shell - Bash Builtin Commands - read

  read
  read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout]
       [-u fd] [name ...]

-u fd

Read input from file descriptor fd.

%
Bash Shell - Bash Builtin Commands - shopt

  shopt
  shopt [-pqsu] [-o] [optname ...]

Toggle the values of variables controlling optional shell behavior. With
no options, or with the `-p' option, a list of all settable options is
displayed, with an indication of whether or not each is set. The `-p'
option causes output to be displayed in a form that may be reused as
input.

%
Bash Shell - Bash Builtin Commands - shopt

  shopt
  shopt [-pqsu] [-o] [optname ...]

-s

Enable (set) each optname.

%
Bash Shell - Bash Builtin Commands - shopt

  shopt
  shopt [-pqsu] [-o] [optname ...]

-u

Disable (unset) each optname.

%
Bash Shell - Bash Builtin Commands - shopt

  shopt
  shopt [-pqsu] [-o] [optname ...]

-q

Suppresses normal output; 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.

%
Bash Shell - Bash Builtin Commands - shopt

  shopt
  shopt [-pqsu] [-o] [optname ...]

-o

Restricts the values of optname to be those defined for the `-o' option
to the set builtin.

%
Bash Shell - Bash Builtin Commands - shopt

  shopt
  shopt [-pqsu] [-o] [optname ...]

If either `-s' or `-u' is used with no optname arguments, the display is
limited to those options which are set or unset, respectively.

Unless otherwise noted, the shopt options are disabled (off) by default.

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

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

cdable_vars

If this is 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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

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 a character too many. If a
correction is found, the corrected path is printed, and the command
proceeds. This option is only used by interactive shells.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

checkhash

If this is 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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

checkwinsize

If set, Bash checks the window size after each command and, if
necessary, updates the values of LINES and COLUMNS.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

dotglob

If set, Bash includes filenames beginning with a `.' in the results of
filename expansion.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

execfail

If this is 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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

expand_aliases

If set, aliases are expanded as described below under Aliases, 6.6
Aliases. This option is enabled by default for interactive shells.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

extglob

If set, the extended pattern matching features described above are
enabled.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

histreedit

If set, and Readline is being used, a user is given the opportunity to
re-edit a failed history substitution.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

hostcomplete

If set, and Readline is being used, Bash will attempt to perform
hostname completion when a word containing a `@' is being completed.
This option is enabled by default.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

huponexit

If set, Bash will send SIGHUP to all jobs when an interactive login
shell exits.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

interactive_comments

Allow a word beginning with `#' to cause that word and all remaining
characters on that line to be ignored in an interactive shell. This
option is enabled by default.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

lithist

If enabled, and the cmdhist option is enabled, multi-line commands are
saved to the history with embedded newlines rather than using semicolon
separators where possible.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

login_shell

The shell sets this option if it is started as a login shell.

The value may not be changed.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

mailwarn

If set, and a file that Bash is checking for mail has been accessed
since the last time it was checked, the message "The mail in mailfile
has been read" is displayed.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

nocaseglob

If set, Bash matches filenames in a case-insensitive fashion when
performing filename expansion.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

nullglob

If set, Bash allows filename patterns which match no files to expand to
a null string, rather than themselves.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

progcomp

If set, the programmable completion facilities are enabled. This option
is enabled by default.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

promptvars

If set, prompt strings undergo variable and parameter expansion after
being expanded. This option is enabled by default.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

restricted_shell

The shell sets this option if it is started in restricted mode. 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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

shift_verbose

If this is set, the shift builtin prints an error message when the shift
count exceeds the number of positional parameters.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

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.

%
Bash Shell - Bash Builtin Commands - shopt options

  shopt [-pqsu] [-o] [optname ...]

xpg_echo

If set, the echo builtin expands backslash-escape sequences by default.

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

%
Bash Shell - Bash Builtin Commands

  source
  source filename

A synonym for ..

%
Bash Shell - Bash Builtin Commands - type

  type
  type [-afptP] [name ...]

For each name, indicate how it would be interpreted if used as a command
name.

%
Bash Shell - Bash Builtin Commands - type

  type
  type [-afptP] [name ...]

If the `-t' option is used, type prints a single word which is one of
`alias', `function', `builtin', `file' or `keyword', if name is an
alias, shell function, shell builtin, disk file, or shell reserved word,
respectively. If the name is not found, then nothing is printed, and
type returns a failure status.

%
Bash Shell - Bash Builtin Commands - type

  type
  type [-afptP] [name ...]

If the `-p' option is used, type either returns the name of the disk
file that would be executed, or nothing if `-t' would not return `file'.

%
Bash Shell - Bash Builtin Commands - type

  type
  type [-afptP] [name ...]

The `-P' option forces a path search for each name, even if `-t' would
not return `file'.

%
Bash Shell - Bash Builtin Commands - type

  type
  type [-afptP] [name ...]

If a command is hashed, `-p' and `-P' print the hashed value, not
necessarily the file that appears first in $PATH.

%
Bash Shell - Bash Builtin Commands - type

  type
  type [-afptP] [name ...]

If the `-a' option is used, type returns all of the places that contain
an executable named file. This includes aliases and functions, if and
only if the `-p' option is not also used.

%
Bash Shell - Bash Builtin Commands - type

  type
  type [-afptP] [name ...]

If the `-f' option is used, type does not attempt to find shell
functions, as with the command builtin.

The return status is zero if any of the names are found, non-zero if
none are found. typeset

%
Bash Shell - Bash Builtin Commands

  typeset [-afFrxi] [-p] [name[=value]]

The typeset command is supplied for compatibility with the Korn shell;
however, it has been deprecated in favor of the declare builtin command.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

ulimit provides control over the resources available to processes
started by the shell, on systems that allow such control.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-S

Change and report the soft limit associated with a resource.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-H

Change and report the hard limit associated with a resource.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-a

All current limits are reported.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-c

The maximum size of core files created.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-d

The maximum size of a process's data segment.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-f

The maximum size of files created by the shell.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-l

The maximum size that may be locked into memory.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-m

The maximum resident set size.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-n

The maximum number of open file descriptors.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-p

The pipe buffer size.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-s

The maximum stack size.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-t

The maximum amount of cpu time in seconds.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-u

The maximum number of processes available to a single user.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

-v

The maximum amount of virtual memory available to the process.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

If limit is given, it is the new value of the specified resource; the
special limit values hard, soft, and unlimited stand for the current
hard limit, the current soft limit, and no limit, respectively.
Otherwise, the current value of the soft limit for the specified
resource is printed, unless the `-H' option is supplied. When setting
new limits, if neither `-H' nor `-S' is supplied, both the hard and soft
limits are set. 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 `-n' and `- u', which are
unscaled values.

%
Bash Shell - Bash Builtin Commands - ulimit

  ulimit
  ulimit [-acdflmnpstuvSH] [limit]

The return status is zero unless an invalid option or argument is
supplied, or an error occurs while setting a new limit.

%
Bash Shell - Bash Builtin Commands - unalias

unalias

unalias [-a] [name ... ]

Remove each name from the list of aliases. If `-a' is supplied, all
aliases are removed. Aliases are described in 6.6 Aliases.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

If no options or arguments are supplied, set displays the names and
values of all shell variables and functions, sorted according to the
current locale, in a format that may be reused as input.

When options are supplied, they set or unset shell attributes.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-a

Mark variables and function which are modified or created for export to
the environment of subsequent commands.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-b

Cause the status of terminated background jobs to be reported
immediately, rather than before printing the next primary prompt.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-e

Exit immediately if a simple command exits with a non-zero status,
unless the command that fails is part of an until or while loop, part of
an if statement, part of a && or || list, or if the command's return
status is being inverted using !. A trap on ERR, if set, is executed
before the shell exits.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-f

Disable file name generation (globbing).

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-h

Locate and remember (hash) commands as they are looked up for execution.
This option is enabled by default.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-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.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-m

Job control is enabled.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-n

Read commands but do not execute them; this may be used to check a
script for syntax errors. This option is ignored by interactive shells.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-o option-name

Set the option corresponding to option-name:

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  allexport - Same as -a.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  braceexpand - Same as -B.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  emacs - Use an emacs-style line editing interface.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  errexit - Same as -e.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  hashall - Same as -h.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  histexpand - Same as -H.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  history - Enable command history, as described in 9.1 Bash History
Facilities. This option is on by default in interactive shells.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  ignoreeof - An interactive shell will not exit upon reading EOF.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  keyword - Same as -k.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  monitor - Same as -m.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  noclobber - Same as -C.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  noexec - Same as -n.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  noglob - Same as -f.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  nolog - Currently ignored.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  notify - Same as -b.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  nounset - Same as -u.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  onecmd - Same as -t.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  physical - Same as -P.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  posix - Change the behavior of Bash where the default operation
differs from the POSIX 1003.2 standard to match the standard. This is
intended to make Bash behave as a strict superset of that standard.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  privileged - Same as -p.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  verbose - Same as -v.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  vi - Use a vi-style line editing interface.

%
Bash Shell - Bash Builtin Commands - set -o option

  set [-o option]

  xtrace - Same as -x.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-p - Turn on privileged mode. In this mode, the $BASH_ENV and $ENV files
are not processed, shell functions are not inherited from the
environment, and the SHELLOPTS variable, if it appears in the
environment, is 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

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-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.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-t

Exit after reading and executing one command.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-u

Treat unset variables as an error when performing parameter expansion.
An error message will be written to the standard error, and a
non-interactive shell will exit.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-v

Print shell input lines as they are read.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-x

Print a trace of simple commands and their arguments after they are
expanded and before they are executed.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-B

The shell will perform brace expansion. This option is on by default.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-C

Prevent output redirection using `>', `>&', and `<>' from overwriting
existing files.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-H

Enable `!' style history substitution. This option is on by default for
interactive shells.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-P

If set, do not follow symbolic links when performing commands such as cd
which change the current directory. The physical directory is used
instead. By default, Bash follows the logical chain of directories when
performing commands which change the current directory.

For example, if `/usr/sys' is a symbolic link to `/usr/local/sys' then:

  $ cd /usr/sys; echo $PWD/usr/sys$ cd ..; pwd /usr

If set -P is on, then:

$ cd /usr/sys; echo $PWD/usr/local/sys$ cd ..; pwd /usr/local

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

--

If no arguments follow this option, then the positional parameters are
unset. Otherwise, the positional parameters are set to the arguments,
even if some of them begin with a `-'.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

-

Signal the end of options, cause all remaining arguments to be assigned
to the positional parameters. The `-x' and `-v' options are turned off.
If there are no arguments, the positional parameters remain unchanged.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

Using `+' rather than `-' causes these options to be turned off. The
options can also be used upon invocation of the shell. The current set
of options may be found in $-.

%
Bash Shell - Bash Builtin Commands - set

  set
  set [--abefhkmnptuvxBCHP] [-o option] [argument ...]

The remaining N arguments are positional parameters and are assigned, in
order, to $1, $2, ... $N. The special parameter # is set to N.

The return status is always zero unless an invalid option is supplied.

%
Bash Shell - Special Builtins

break : . continue eval exec exit export readonly return setshift trap
unset

For historical reasons, the POSIX 1003.2 standard has classified several
builtin commands as special. When Bash is executing in POSIX mode, the
special builtins differ from other builtin commands in three respects:

1. Special builtins are found before shell functions during command
lookup.

2. If a special builtin returns an error status, a non-interactive shell
exits.

3. Assignment statements preceding the command stay in effect in the
shell environment after the command completes.

%
Bash Shell - Special Builtins

break : . continue eval exec exit export readonly return setshift trap
unset

When Bash is not executing in POSIX mode, these builtins behave no
differently than the rest of the Bash builtin commands. The Bash POSIX
mode is described in 6.11 Bash POSIX Mode.

%
Bash Shell - Special Builtins

These are the POSIX special builtins:

break : . continue eval exec exit export readonly return setshift trap
unset

%
Bash Shell - Bourne Shell Variables

CDPATH

A colon-separated list of directories used as a search path for the cd
builtin command.

%
Bash Shell - Bourne Shell Variables

HOME

The current user's home directory; the default for the cd builtin
command. The value of this variable is also used by tilde expansion.

%
Bash Shell - Bourne Shell Variables

IFS

A list of characters that separate fields; used when the shell splits
words as part of expansion.

%
Bash Shell - Bourne Shell Variables

MAIL

If this parameter is set to a filename and the MAILPATH variable is not
set, Bash informs

The user of the arrival of mail in the specified file.

%
Bash Shell - Bourne Shell Variables

MAILPATH

A colon-separated list of filenames which the shell periodically checks
for new mail.

Each list entry can specify the message that is printed when new mail
arrives in the mail file by separating the file name from the message
with a `?'. When used in the text of the message, $_ expands to the name
of the current mail file.

%
Bash Shell - Bourne Shell Variables

OPTARG

The value of the last option argument processed by the getopts builtin.

%
Bash Shell - Bourne Shell Variables

OPTIND

The index of the last option argument processed by the getopts builtin.

%
Bash Shell - Bourne Shell Variables

PATH

A colon-separated list of directories in which the shell looks for
commands.

%
Bash Shell - Bourne Shell Variables

PS1

The primary prompt string. The default value is `\s-\v\$ '.

Controlling the Prompt, for the complete list of escape sequences that
are expanded before PS1 is displayed.

%
Bash Shell - Bourne Shell Variables

PS2

The secondary prompt string. The default value is `> '.

%
Bash Shell - Bash Variables

BASH

The full pathname used to execute the current instance of Bash.

%
Bash Shell - Bash Variables

BASH_ENV

If this variable is set when Bash is invoked to execute a shell script,
its value is expanded and used as the name of a startup file to read
before executing the script.

%
Bash Shell - Bash Variables

BASH_VERSION

The version number of the current instance of Bash.

%
Bash Shell - Bash Variables

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 Shell - Bash Variables

BASH_VERSINFO[0]

The major version number (the release).

%
Bash Shell - Bash Variables

BASH_VERSINFO[1]

The minor version number (the version).

%
Bash Shell - Bash Variables

BASH_VERSINFO[2]

The patch level.

%
Bash Shell - Bash Variables

BASH_VERSINFO[3]

The build version.

%
Bash Shell - Bash Variables

BASH_VERSINFO[4]

The release status (e.g., beta1).

%
Bash Shell - Bash Variables

BASH_VERSINFO[5]

The value of MACHTYPE.

%
Bash Shell - Bash Variables

COLUMNS

Used by the select builtin command to determine the terminal width when
printing selection lists. Automatically set upon receipt of a SIGWINCH.

%
Bash Shell - Bash Variables

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.

%
Bash Shell - Bash Variables

COMP_LINE

The current command line. This variable is available only in shell
functions and external commands invoked by the programmable completion
facilities.

%
Bash Shell - Bash Variables

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.

%
Bash Shell - Bash Variables

COMP_WORDS

An array variable consisting of the individual words in the current
command line. This variable is available only in shell functions invoked
by the programmable completion facilities.

%
Bash Shell - Bash Variables

COMPREPLY

An array variable from which Bash reads the possible completions
generated by a shell function invoked by the programmable completion
facility.

%
Bash Shell - Bash Variables

DIRSTACK

An array variable 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.

%
Bash Shell - Bash Variables

EUID

The numeric effective user id of the current user. This variable is
readonly.

%
Bash Shell - Bash Variables

FCEDIT

The editor used as a default by the `-e' option to the fc builtin
command.

%
Bash Shell - Bash Variables

FIGNORE

A colon-separated list of suffixes to ignore when performing filename
completion. A file name whose suffix matches one of the entries in
FIGNORE is excluded from the list of matched file names. A sample value
is `.o:~'

%
Bash Shell - Bash Variables

FUNCNAME

The name of any currently-executing shell function. This variable exists
only when a shell function is executing. Assignments to FUNCNAME have no
effect and return an error status. If FUNCNAME is unset, it loses its
special properties, even if it is subsequently reset.

%
Bash Shell - Bash Variables

GLOBIGNORE

A colon-separated list of patterns defining the set of filenames to be
ignored by filename expansion. If a filename matched by a filename
expansion pattern also matches one of the patterns in GLOBIGNORE, it is
removed from the list of matches.

%
Bash Shell - Bash Variables

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. histchars

Up to three characters which control history expansion, quick
substitution, and tokenization. The first character is the history
expansion character, that is, the character which signifies the start of
a history expansion, normally `!'. The second character is the character
which signifies `quick substitution' when seen as the first character on
a line, normally `^'. The optional third character is the character
which indicates that the remainder of the line is a comment when found
as the first character of a word, usually `#'. 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.

%
Bash Shell - Bash Variables

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.

%
Bash Shell - Bash Variables

HISTCONTROL

A value of `ignorespace' means to not enter lines which begin with a
space or tab into the history list. A value of `ignoredups' means to not
enter lines which match the last entered line. A value of `ignoreboth'
combines the two options.

Unset, or set to any other value than those above, means to save all
lines on the history list. 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.

%
Bash Shell - Bash Variables

HISTFILE

The name of the file to which the command history is saved. The default
value is `~/.bash_history'.

%
Bash Shell - Bash Variables

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. The history
file is also truncated to this size after writing it when an interactive
shell exits. The default value is 500.

%
Bash Shell - Bash Variables

HISTIGNORE

A colon-separated list of patterns used to decide which command lines
should be saved on the history list. Each pattern is anchored at the
beginning of the line and must match the complete line (no implicit `*'
is appended). Each pattern is tested against the line after the checks
specified by HISTCONTROL are applied. In addition to the normal shell
pattern matching characters, `&' matches the previous history line. `&'
may be escaped using a backslash; the backslash is removed before
attempting a match. The second and subsequent lines of a multi-line
compound command are not tested, and are added to the history regardless
of the value of HISTIGNORE.

HISTIGNORE subsumes the function of HISTCONTROL. A pattern of `&' is
identical to ignoredups, and a pattern of `[ ]*' is identical to
ignorespace. Combining these two patterns, separating them with a colon,
provides the functionality of ignoreboth.

%
Bash Shell - Bash Variables

HISTSIZE

The maximum number of commands to remember on the history list. The
default value is 500.

%
Bash Shell - Bash Variables

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, Bash attempts to read `/etc/hosts' to
obtain the list of possible hostname completions. When HOSTFILE is
unset, the hostname list is cleared.

%
Bash Shell - Bash Variables

HOSTNAME

The name of the current host.

%
Bash Shell - Bash Variables

HOSTTYPE

A string describing the machine Bash is running on.

%
Bash Shell - Bash Variables

IGNOREEOF

Controls the action of the shell on receipt of an EOF character as the
sole input. If set, the value denotes the number of consecutive EOF
characters that can be read as the first character on an input line
before the shell will exit. If the variable exists but does not have a
numeric value (or has no value) then the default is 10. If the variable
does not exist, then EOF signifies the end of input to the shell. This
is only in effect for interactive shells.

%
Bash Shell - Bash Variables

INPUTRC

The name of the Readline initialization file, overriding the default of
`~/.inputrc'.

%
Bash Shell - Bash Variables

LANG

Used to determine the locale category for any category not specifically
selected with a variable starting with LC_.

%
Bash Shell - Bash Variables

LC_ALL

This variable overrides the value of LANG and any other LC_ variable
specifying a locale category.

%
Bash Shell - Bash Variables

LC_COLLATE

This variable determines the collation order used when sorting the
results of filename expansion, and determines the behavior of range
expressions, equivalence classes, and collating sequences within
filename expansion and pattern matching.

%
Bash Shell - Bash Variables

LC_CTYPE

This variable determines the interpretation of characters and the
behavior of character classes within filename expansion and pattern
matching.

%
Bash Shell - Bash Variables

LC_MESSAGES

This variable determines the locale used to translate double-quoted
strings preceded by a `$'.

%
Bash Shell - Bash Variables

LC_NUMERIC

This variable determines the locale category used for number formatting.

%
Bash Shell - Bash Variables

LINENO

The line number in the script or shell function currently executing.

%
Bash Shell - Bash Variables

LINES

Used by the select builtin command to determine the column length for
printing selection lists. Automatically set upon receipt of a SIGWINCH.

%
Bash Shell - Bash Variables

MACHTYPE

A string that fully describes the system type on which Bash is
executing, in the standard GNU cpu-company-system format.

%
Bash Shell - Bash Variables

MAILCHECK

How often (in seconds) that the shell should check for mail in the files
specified in the

MAILPATH or MAIL variables. 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.

%
Bash Shell - Bash Variables

OLDPWD

The previous working directory as set by the cd builtin.

%
Bash Shell - Bash Variables

OPTERR

If set to the value 1, Bash displays error messages generated by the
getopts builtin command.

%
Bash Shell - Bash Variables

OSTYPE

A string describing the operating system Bash is running on.

%
Bash Shell - Bash Variables

PIPESTATUS

An array variable containing a list of exit status values from the
processes in the most-recently-executed foreground pipeline (which may
contain only a single command).

%
Bash Shell - Bash Variables

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.

%
Bash Shell - Bash Variables

PPID

The process ID of the shell's parent process. This variable is readonly.

%
Bash Shell - Bash Variables

PROMPT_COMMAND

If set, the value is interpreted as a command to execute before the
printing of each primary prompt ($PS1).

%
Bash Shell - Bash Variables

PS3

The value of this variable is used as the prompt for the select command.
If this variable is not set, the select command prompts with `#? '

%
Bash Shell - Bash Variables

PS4

The value is the prompt printed before the command line is echoed when
the `-x' option is set. The first character of PS4 is replicated
multiple times, as necessary, to indicate multiple levels of
indirection. The default is `+'.

%
Bash Shell - Bash Variables

PWD

The current working directory as set by the cd builtin.

%
Bash Shell - Bash Variables

RANDOM

Each time this parameter is referenced, a random integer between 0 and
32767 is generated. Assigning a value to this variable seeds the random
number generator.

%
Bash Shell - Bash Variables

REPLY

The default variable for the read builtin.

%
Bash Shell - Bash Variables

SECONDS

This variable expands to the number of seconds since the shell was
started. Assignment to this variable resets the count to the value
assigned, and the expanded value becomes the value assigned plus the
number of seconds since the assignment.

%
Bash Shell - Bash Variables

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. 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 readonly.

%
Bash Shell - Bash Variables

SHLVL

Incremented by one each time a new instance of Bash is started. This is
intended to be a count of how deeply your Bash shells are nested.

%
Bash Shell - Bash Variables - TIMEFORMAT

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.

%
Bash Shell - Bash Variables - TIMEFORMAT

TIMEFORMAT

%%

A literal `%'.

%
Bash Shell - Bash Variables - TIMEFORMAT

%[p][l]R

The elapsed time in seconds.

%
Bash Shell - Bash Variables - TIMEFORMAT

%[p][l]U

The number of CPU seconds spent in user mode.

%
Bash Shell - Bash Variables - TIMEFORMAT

%[p][l]S

The number of CPU seconds spent in system mode.

%
Bash Shell - Bash Variables - TIMEFORMAT

%P

The CPU percentage, computed as (%U + %S) / %R.

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

The optional l specifies a longer format, including minutes, of the form
MMmSS.FFs.

The value of p determines whether or not the fraction is included.

%
Bash Shell - Bash Variables - TIMEFORMAT

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.

%
Bash Shell - Bash Variables

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 interative shell, the value is interpreted as the number of
seconds to wait for input after issuing the primary prompt when the
shell is interactive. Bash terminates after that number of seconds if
input does not arrive.

%
Bash Shell - Bash Variables

UID

The numeric real user id of the current user. This variable is readonly.

%
Bash Shell - Invoking Bash 

bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o option] 
     [-O shopt_option] [argument ...]

bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o option] [-O shopt_option] 
     -c string [argument ...]

bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o option] 
     [-O shopt_option] [argument ...]

In addition to the single-character shell command-line options, there
are several multi-character options that you can use. These options must
appear on the command line before the single-character options to be
recognized.

%
Bash Shell - Invoking Bash 

--dump-po-strings

A list of all double-quoted strings preceded by `$' is printed on the
standard ouput in the GNU gettext PO (portable object) file format.
Equivalent to `-D' except for the output format.

%
Bash Shell - Invoking Bash 

--dump-strings

Equivalent to `-D'.

%
Bash Shell - Invoking Bash 

--help

Display a usage message on standard output and exit sucessfully.

%
Bash Shell - Invoking Bash 

--init-file filename

%
Bash Shell - Invoking Bash 

--rcfile filename

Execute commands from filename (instead of `~/.bashrc') in an
interactive shell.

%
Bash Shell - Invoking Bash 

--login

Equivalent to `-l'.

%
Bash Shell - Invoking Bash 

--noediting

Do not use the GNU Readline library to read command lines when the shell
is interactive.

%
Bash Shell - Invoking Bash 

--noprofile

Don't load the system-wide startup file `/etc/profile' or any of the
personal initialization files `~/.bash_profile', `~/.bash_login', or
`~/.profile' when

Bash is invoked as a login shell.

%
Bash Shell - Invoking Bash 

--norc

Don't read the `~/.bashrc' initialization file in an interactive shell.
This is on by default if the shell is invoked as sh.

%
Bash Shell - Invoking Bash 

--posix

Change the behavior of Bash where the default operation differs from the
POSIX 1003.2 standard to match the standard. This is intended to make
Bash behave as a strict superset of that standard.

%
Bash Shell - Invoking Bash 

--restricted

Make the shell a restricted shell.

%
Bash Shell - Invoking Bash 

--verbose

Equivalent to `-v'. Print shell input lines as they're read.

%
Bash Shell - Invoking Bash 

--version

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

%
Bash Shell - Invoking Bash - options

-c string

Read and execute commands from string after processing the options, then
exit. Any remaining arguments are assigned to the positional parameters,
starting with $0.

%
Bash Shell - Invoking Bash - options

-i

Force the shell to run interactively. Interactive shells are described
in 6.3 Interactive Shells.

%
Bash Shell - Invoking Bash - options

-l

Make this shell act as if it had been directly invoked by login. When
the shell is interactive, this is equivalent to starting a login shell
with `exec -l bash'. When the shell is not interactive, the login shell
startup files will be executed. `exec bash -l' or `exec bash --login'
will replace the current shell with a Bash login shell.

%
Bash Shell - Invoking Bash - options

-r

Make the shell a restricted shell.

%
Bash Shell - Invoking Bash - options

-s

If this 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.

%
Bash Shell - Invoking Bash - options

-D

A list of all double-quoted strings preceded by `$' is printed on the
standard ouput.

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.

%
Bash Shell - Invoking Bash - options

 [-+]O [shopt_option]

shopt_option is one of the shell options accepted by the shopt builtin.
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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Bash Shell - Invoking Bash 

--

A -- signals the end of options and disables further option processing.
Any arguments after the -- are treated as filenames and arguments.

%
Bash Shell - Invoking Bash - options

A login shell is one whose first character of argument zero is `-', or
one invoked with the `- -login' option.

%
Bash Shell - Invoking Bash - options

An interactive shell is one started without non-option arguments, unless
`-s' is specified, without specifying the `-c' option, and whose input
and output are both connected to terminals (as determined by isatty(3)),
or one started with the `-i' option.

%
Bash Shell - Invoking Bash - options

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. When 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.

%
Bash Shell - Bash Startup Files

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.

%
Bash Shell - Bash Startup Files

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

%
Bash Shell - Bash Startup Files

When an interactive shell that is not a login shell is started, Bash
reads and executes commands from `~/.bashrc', if that file exists. This
may be inhibited by using the `--norc' option.

%
Bash Shell - Bash Startup Files

The `--rcfile file' option will force Bash to read and execute commands
from file instead of `~/.bashrc'.

So, typically, your `~/.bash_profile' contains the line

  if [ -f ~/.bashrc ]; then . ~/.bashrc; fi

after (or before) any login-specific initializations.

%
Bash Shell - Bash Startup Files

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

  if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi

but the value of the PATH variable is not used to search for the file
name. As noted above, if a non-interactive shell is invoked with the
`--login' option, Bash  attempts to read and execute commands from the
login shell startup files.

%
Bash Shell - Bash Startup Files

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.

%
Bash Shell - Bash Startup Files

When invoked as an interactive login shell, or as 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

%
Bash Shell - Bash Startup Files

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.

%
Bash Shell - Bash Startup Files

When invoked as sh, Bash enters POSIX mode after the startup files are
read.

%
Bash Shell - Bash Startup Files

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 Shell - Bash Startup Files

Bash attempts to determine when it is being run by the remote shell
daemon, usually rshd. If Bash determines it is being run by rshd, it
reads and executes commands from `~/.bashrc', if that file exists and is
readable. It will not do this if invoked as sh. The `--norc' option may
be used to inhibit this behavior, and the `--rcfile' option may be used
to force another file to be read, but rshd does not generally invoke the
shell with those options or allow them to be specified.

%
Bash Shell - Bash Startup Files

If Bash 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 variable, if it appears in the environment, is ignored,
and the effective user id is set to the real user id. If the -p option
is supplied at invocation, the startup behavior is the same, but the
effective user id is not reset.

%
Bash Shell - What is an Interactive Shell?

An interactive shell is one started without non-option arguments, unless
`-s' is specified, without specifiying the `-c' option, and whose input
and output are both connected to terminals (as determined by isatty(3)),
or one started with the `-i' option.

%
Bash Shell - What is an Interactive Shell?

An interactive shell generally reads from and writes to a user's
terminal.

%
Bash Shell - What is an Interactive Shell?

The `-s' invocation option may be used to set the positional parameters
when an interactive shell is started.

%
Bash Shell - Is this Shell Interactive?

To determine within a startup script whether or not Bash is running
interactively, test the value of the `-' special parameter. It contains
i when the shell is interactive. For example:

  case "$-" in*
    i*)	echo This shell is interactive ;;
     *)	echo This shell is not interactive ;;
  esac

%
Bash Shell - Is this Shell Interactive?

Startup scripts may examine the variable PS1; it is unset
in non-interactive shells, and set in interactive shells. Thus:

  if [ -z "$PS1" ]; then
        echo This shell is not interactive
  else
        echo This shell is interactive
  fi

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 1. Startup files are read and executed as described in 6.2 Bash Startup
Files.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 2. Job Control is enabled by default. When job control is in
effect, Bash ignores the keyboard-generated job control signals SIGTTIN,
SIGTTOU, and SIGTSTP.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 3. Bash expands and displays PS1 before reading the first line of a
command, and expands and displays PS2 before reading the second and
subsequent lines of a multi-line command.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 4. Bash executes the value of the PROMPT_COMMAND variable as a
command before printing the primary prompt, $PS1.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 5. Readline is used to read commands from the user's terminal.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 6. Bash inspects the value of the ignoreeof option to set -o
instead of exiting immediately when it receives an EOF on its standard
input when reading a command.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 7. Command history and history expansion are enabled by default.
Bash will save the command history to the file named by $HISTFILE when
an interactive shell exits.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 8. Alias expansion is performed by default.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 9. In the absence of any traps, Bash ignores SIGTERM.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

10. In the absence of any traps, SIGINT is caught and handled . SIGINT
will interrupt some shell builtins.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 11. An interactive login shell sends a SIGHUP to all jobs on exit
if the hupoxexit shell option has been enabled.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 12. The `-n' invocation option is ignored, and `set -n' has no
effect.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 13. Bash will check for mail periodically, depending on the
values of the MAIL, MAILPATH, and MAILCHECK shell variables.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 14. Expansion errors due to references to unbound shell variables
after `set -u' has been enabled will not cause the shell to exit.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 15. The shell will not exit on expansion errors caused by var
being unset or null in ${var:?word} expansions.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 16. Redirection errors encountered by shell builtins will not cause the
shell to exit.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 17. When running in POSIX mode, a special builtin returning an
error status will not cause the shell to exit.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 18. A failed exec will not cause the shell to exit.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 19. Parser syntax errors will not cause the shell to exit.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 20. Simple spelling correction for directory arguments to the cd
builtin is enabled by default.

%
Bash Shell - Interactive Shell Behavior

When the shell is running interactively, it changes its behavior in
several ways.

Change 21. The shell will check the value of the TMOUT variable and exit
if a command is not read within the specified number of seconds after
printing $PS1.

%
Bash Shell - Bash Conditional Expressions

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

Expressions may be unary or binary. Unary expressions are often used to
examine the status of a file. There are string operators and numeric
comparison operators as well. If the 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.

%
Bash Shell - Bash Conditional Expressions

  -a file

True if file exists.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -b file

True if file exists and is a block special file.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -c file

True if file exists and is a character special file.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -d file

True if file exists and is a directory.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -e file

True if file exists.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -f file

True if file exists and is a regular file.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -g file

True if file exists and its set-group-id bit is set.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -h file

True if file exists and is a symbolic link.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -k file

True if file exists and its "sticky" bit is set.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -p file

True if file exists and is a named pipe (FIFO).

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -r file

True if file exists and is readable.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -s file

True if file exists and has a size greater than zero.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -t fd

True if file descriptor fd is open and refers to a terminal.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -u file

True if file exists and its set-user-id bit is set.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -w file

True if file exists and is writable.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -x file

True if file exists and is executable.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -O file

True if file exists and is owned by the effective user id.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -G file

True if file exists and is owned by the effective group id.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -L file

True if file exists and is a symbolic link.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -S file

True if file exists and is a socket.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -N file

True if file exists and has been modified since it was last read.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  file1 -nt file2

True if file1 is newer (according to modification date) than file2, or
if file1 exists and file2 does not.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  file1 -ot file2

True if file1 is older than file2, or if file2 exists and file1 does
not.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  file1 -ef file2

True if file1 and file2 refer to the same device and inode numbers.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -o optname

True if shell option optname is enabled. The list of options appears in
the description of the `-o' option to the set builtin.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -z string

True if the length of string is zero.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  -n string
     string

True if the length of string is non-zero.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  string1 == string2

True if the strings are equal. `=' may be used in place of `==' for
strict POSIX compliance.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  string1 != string2

True if the strings are not equal.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  string1 < string2

True if string1 sorts before string2 lexicographically in the current
locale.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  string1 > string2

True if string1 sorts after string2 lexicographically in the current
locale.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Bash Conditional Expressions

  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.

Conditional expressions are used by the [[ compound command and the test
and [ builtin commands.

%
Bash Shell - Shell Arithmetic

The shell allows arithmetic expressions to be evaluated, as one of the
shell expansions or by the let builtin.

%
Bash Shell - Shell Arithmetic

Evaluation is done in fixed-width integers with no check for overflow,
though division by 0 is trapped and flagged as an error. The operators
and their precedence and associativity are the same as in the C
language.

%
Bash Shell - Shell Arithmetic - Precedence Level: 1

id++ id--

variable post-increment and post-decrement

%
Bash Shell - Shell Arithmetic - Precedence Level: 2

++id --id

variable pre-increment and pre-decrement

%
Bash Shell - Shell Arithmetic - Precedence Level: 3

- +

unary minus and plus

%
Bash Shell - Shell Arithmetic - Precedence Level: 4

! ~

logical and bitwise negation

%
Bash Shell - Shell Arithmetic - Precedence Level: 5

**

exponentiation

%
Bash Shell - Shell Arithmetic - Precedence Level: 6

* / %

multiplication, division, remainder

%
Bash Shell - Shell Arithmetic - Precedence Level: 7

+ -

addition, subtraction

%
Bash Shell - Shell Arithmetic - Precedence Level: 8

<< >>

left and right bitwise shifts

%
Bash Shell - Shell Arithmetic - Precedence Level: 9

<= >= < >

comparison

%
Bash Shell - Shell Arithmetic - Precedence Level: 10

== !=

equality and inequality

%
Bash Shell - Shell Arithmetic - Precedence Level: 11

&

bitwise AND

%
Bash Shell - Shell Arithmetic - Precedence Level: 12

^

bitwise exclusive OR

%
Bash Shell - Shell Arithmetic - Precedence Level: 13

|

bitwise OR

%
Bash Shell - Shell Arithmetic - Precedence Level: 14

&&

logical AND

%
Bash Shell - Shell Arithmetic - Precedence Level: 15

||

logical OR

%
Bash Shell - Shell Arithmetic - Precedence Level: 16

expr ? expr : expr

conditional evaluation

%
Bash Shell - Shell Arithmetic - Precedence Level: 17

= *= /= %= += -= <<= >>= &= ^= |=

assignment

%
Bash Shell - Shell Arithmetic - Precedence Level: 18

expr1 , expr2

comma

%
Bash Shell - Shell Arithmetic

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. The value of a variable is evaluated as an
arithmetic expression when it is referenced. A shell variable need not
have its integer attribute turned on to be used in an expression.

%
Bash Shell - Shell Arithmetic

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 base is a decimal number between 2 and 64 representing
the arithmetic base, and n is a number in that base. If base# is
omitted, then base 10 is used. The digits greater than 9 are represented
by the lowercase letters, the uppercase letters, `@', and `_', in that
order. If base is less than or equal to 36, lowercase and uppercase
letters may be used interchangably to represent numbers between 10 and
35.

%
Bash Shell - Shell Arithmetic

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

%
Bash Shell - Aliases

Aliases allow a string to be substituted for a word when it is used as
the first word of a simple command. The shell maintains a list of
aliases that may be set and unset with the alias and unalias builtin
commands.

%
Bash Shell - Aliases

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 alias name and the replacement text may contain any valid shell
input, including shell metacharacters, with the exception that the alias
name may not contain `='. 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
space or tab character, then the next command word following the alias
is also checked for alias expansion.

%
Bash Shell - Aliases

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

%
Bash Shell - Aliases

There is no mechanism for using arguments in the replacement text, as in
csh. If arguments are needed, a shell function should be used.

%
Bash Shell - Aliases

Aliases are not expanded when the shell is not interactive, unless the
expand_aliases shell option is set using shopt.

%
Bash Shell - Aliases

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.

%
Bash Shell - Aliases

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.

%
Bash Shell - Aliases

For almost every purpose, shell functions are preferred over aliases.

%
Bash Shell - Arrays

Bash provides one-dimensional array variables. Any variable may be used
as an 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. Arrays are zero- based.

%
Bash Shell - Arrays

An 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 greater than or equal to zero. 

%
Bash Shell - Arrays

To explicitly declare an array, use

declare -a name

The syntax

declare -a name[subscript]

is also accepted; the subscript is ignored. Attributes may be specified
for an array variable using the declare and readonly builtins. Each
attribute applies to all members of an array.

%
Bash Shell - Arrays

Arrays are assigned to using compound assignments of the form

name=(value1 ... valuen)

where each value is of the form [[subscript]=]string. If the optional
subscript is 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. This syntax is also accepted by the
declare builtin. Individual array elements may be assigned to using the
name[subscript]=value syntax introduced above.

%
Bash Shell - Arrays

Any element of an array may be referenced using ${name[subscript]}. The
braces are required to avoid conflicts with the shell's filename
expansion operators. If the subscript is `@' or `*', the word expands to
all members of the array name. These subscripts differ only when the
word appears within double quotes. If the word is double-quoted,
${name[*]} expands to a single word with the value of each array member
separated by the first character of the IFS variable, and ${name[@]}
expands each element of name to a separate word. When there are no array
members, ${name[@]} expands to nothing. This is analogous to the
expansion of the special parameters `@' and `*'. ${#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 element
zero.

%
Bash Shell - Arrays

The unset builtin is used to destroy arrays. unset name[subscript]
destroys the array element at index subscript. unset name, where name is
an array, removes the entire array. A subscript of `*' or `@' also
removes the entire array.

%
Bash Shell - Arrays

The declare, local, and readonly builtins each accept a `-a' option to
specify an array.

%
Bash Shell - Arrays

The read builtin accepts a `-a' option to assign a list of words read
from the standard input to an array, and can read values from the
standard input into individual array elements. The set and declare
builtins display array values in a way that allows them to be reused as
input.

%
Bash Shell - Directory Stack Builtins

The directory stack is a list of recently-visited directories. The pushd
builtin adds directories to the stack as it changes the current
directory, and the popd builtin removes specified directories from the
stack and changes the current directory to the directory removed. The
dirs builtin displays the contents of the directory stack.

The contents of the directory stack are also visible as the value of the
DIRSTACK shell variable.

%
Bash Shell - Directory Stack Builtins

  dirs
  dirs [+N | -N] [-clpv]

Display the list of currently remembered directories. Directories are
added to the list with the pushd command; the popd command removes
directories from the list.

%
Bash Shell - Directory Stack Builtins

  dirs
  dirs [+N | -N] [-clpv]

  +N

Displays the Nth directory (counting from the left of the list printed
by dirs when invoked without options), starting with zero.

%
Bash Shell - Directory Stack Builtins

  dirs
  dirs [+N | -N] [-clpv]

  -N

Displays the Nth directory (counting from the right of the list printed
by dirs when invoked without options), starting with zero.

%
Bash Shell - Directory Stack Builtins

  dirs
  dirs [+N | -N] [-clpv]

  -c

Clears the directory stack by deleting all of the elements.

%
Bash Shell - Directory Stack Builtins

  dirs
  dirs [+N | -N] [-clpv]

  -l

Produces a longer listing; the default listing format uses a tilde to
denote the home directory.

%
Bash Shell - Directory Stack Builtins

  dirs
  dirs [+N | -N] [-clpv]

  -p

Causes dirs to print the directory stack with one entry per line.

%
Bash Shell - Directory Stack Builtins

  dirs
  dirs [+N | -N] [-clpv]

  -v

Causes dirs to print the directory stack with one entry per line,
prefixing each entry with its index in the stack.

%
Bash Shell - Directory Stack Builtins

  popd
  popd [+N | -N] [-n]

Remove the top entry from the directory stack, and cd to the new top
directory. When no arguments are given, popd removes the top directory
from the stack and performs a cd to the new top directory. The elements
are numbered from 0 starting at the first directory listed with dirs;
i.e., popd is equivalent to popd +0.

%
Bash Shell - Directory Stack Builtins

  popd
  popd [+N | -N] [-n]

  +N

Removes the Nth directory (counting from the left of the list printed by
dirs), starting with zero.

%
Bash Shell - Directory Stack Builtins

  popd
  popd [+N | -N] [-n]

  -N

Removes the Nth directory (counting from the right of the list printed
by dirs), starting with zero.

%
Bash Shell - Directory Stack Builtins

  popd
  popd [+N | -N] [-n]

  -n

Suppresses the normal change of directory when removing directories from
the stack, so that only the stack is manipulated. pushd

%
Bash Shell - Directory Stack Builtins

  pushd [dir | +N | -N] [-n]

Save the current directory on the top of the directory stack and then cd
to dir. With no arguments, pushd exchanges the top two directories.

%
Bash Shell - Directory Stack Builtins

  pushd [dir | +N | -N] [-n]

  +N

Brings the Nth directory (counting from the left of the list printed by
dirs, starting with zero) to the top of the list by rotating the stack.

%
Bash Shell - Directory Stack Builtins

  pushd [dir | +N | -N] [-n]

  -N

Brings the Nth directory (counting from the right of the list printed by
dirs, starting with zero) to the top of the list by rotating the stack.

%
Bash Shell - Directory Stack Builtins

  pushd [dir | +N | -N] [-n]

  -n

Suppresses the normal change of directory when adding directories to the
stack, so that only the stack is manipulated.

%
Bash Shell - Directory Stack Builtins

  dir

Makes the current working directory be the top of the stack, and then
executes the equivalent of `cd dir'. cds to dir.

%
Bash Shell - Controlling the Prompt

The value of the variable PROMPT_COMMAND is examined just before Bash
prints each primary prompt. If PROMPT_COMMAND is set and has a non-null
value, then the value is executed just as if it had been typed on the
command line.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \a

A bell character.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \d

The date, in "Weekday Month Date" format (e.g., "Tue May 26").

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \D{format}

The format is passed to strftime(3) and the result is inserted into the
prompt string; an empty format results in a locale-specific time
representation. The braces are required.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \e

An escape character.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \h

The hostname, up to the first `.'.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \H

The hostname.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \j

The number of jobs currently managed by the shell.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \l

The basename of the shell's terminal device name.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \n

A newline.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \r

A carriage return.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \s

The name of the shell, the basename of $0 (the portion following the
final slash).

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \t

The time, in 24-hour HH:MM:SS format.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \T

The time, in 12-hour HH:MM:SS format.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \@

The time, in 12-hour am/pm format.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \A

The time, in 24-hour HH:MM format.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \u

The username of the current user.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \v

The version of Bash (e.g., 2.00)

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \V

The release of Bash, version + patchlevel (e.g., 2.00.0)

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \w

The current working directory.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \W

The basename of $PWD.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \!

The history number of this command.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \#

The command number of this command.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \$

If the effective uid is 0, #, otherwise $.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \nnn

The character whose ASCII code is the octal value nnn.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \\

A backslash.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \[

Begin a sequence of non-printing characters. This could be used to embed
a terminal control sequence into the prompt.

%
Bash Shell - Controlling the Prompt - Special Characters

Special characters which can appear in the prompt variables:

  \]

End a sequence of non-printing characters.

%
Bash Shell - Controlling the Prompt

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, while the command
number is the position in the sequence of commands executed during the
current shell session.

%
Bash Shell - Controlling the Prompt

After the prompt 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.

%
Bash Shell - The Restricted Shell

If Bash is started with the name rbash, or the `--restricted' or `-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.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Changing directories with the cd builtin.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Setting or unsetting the values of the SHELL, PATH, ENV, or
    BASH_ENV variables.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Specifying command names containing slashes.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Specifying a filename containing a slash as an argument to the .
    builtin command.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Specifying a filename containing a slash as an argument to the
    `-p' option to the hash builtin command.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Importing function definitions from the shell environment at
    startup.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Parsing the value of SHELLOPTS from the shell environment at
    startup.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Redirecting output using the `>', `>|', `<>', `>&', `&>', and
    `>>' redirection operators.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Using the exec builtin to replace the shell with another
    command.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Adding or deleting builtin commands with the `-f' and `-d'
    options to the enable builtin.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Using the enable builtin command to enable disabled shell
    builtins.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Specifying the `-p' option to the command builtin.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

Disallowed or not performed in a restricted shell:

  * Turning off restricted mode with `set +r' or `set +o
    restricted'.

These restrictions are enforced after any startup files are read.

%
Bash Shell - The Restricted Shell

When a command that is found to be a shell script is executed, rbash
turns off any restrictions in the shell spawned to execute the script.

%
Bash Shell - Bash POSIX Mode

Starting Bash with the `--posix' command-line option or executing `set
-o posix' while Bash is running will cause Bash to conform more closely
to the POSIX 1003.2 standard by changing the behavior to match that
specified by POSIX in areas where the Bash default differs.

%
Bash Shell - Bash POSIX Mode

When invoked as sh, Bash enters POSIX mode after reading the startup
files.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

When a command in the hash table no longer exists, Bash will
re-search $PATH to find the new location. This is also available with
`shopt -s checkhash'.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The message printed by the job control code and builtins when a
job exits with a non- zero status is `Done(status)'.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The message printed by the job control code and builtins when a
job is stopped is `Stopped(signame)', where signame is, for example,
SIGTSTP.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Reserved words may not be aliased.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The POSIX 1003.2 PS1 and PS2 expansions of `!' to the history number and
`!!' to `!' are enabled, and parameter expansion is performed on the
values of PS1 and PS2 regardless of the setting of the promptvars
option.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Interactive comments are enabled by default. (Bash has them on by
default anyway.)

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The POSIX 1003.2 startup files are executed ($ENV) rather than the
normal Bash files.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Tilde expansion is only performed on assignments preceding a command
name, rather than on all assignment statements on the line.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The default history file is `~/.sh_history' (this is the default value
of $HISTFILE).

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The output of `kill -l' prints all the signal names on a single line,
separated by spaces.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Non-interactive shells exit if filename in . filename is not found.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Non-interactive shells exit if a syntax error in an arithmetic expansion
results in an invalid expression.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Redirection operators do not perform filename expansion on the word in
the redirection unless the shell is interactive.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Redirection operators do not perform word splitting on the word in the
redirection.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Function names must be valid shell names. That is, they may not contain
characters other than letters, digits, and underscores, and may not
start with a digit. Declaring a function with an invalid name causes a
fatal syntax error in non-interactive shells.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

POSIX 1003.2 `special' builtins are found before shell functions during
command lookup.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

If a POSIX 1003.2 special builtin returns an error status, a
non-interactive shell exits.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The fatal errors are those listed in the POSIX.2 standard, and include
things like passing incorrect options, redirection errors, variable
assignment errors for assignments preceding the command name, and so on.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

If the cd builtin finds a directory to change to using $CDPATH, the
value it assigns to the PWD variable does not contain any symbolic
links, as if `cd -P' had been executed.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

If CDPATH is set, the cd builtin will not implicitly append the current
directory to it. This means that cd will fail if no valid directory name
can be constructed from any of the entries in $CDPATH, even if the a
directory with the same name as the name given as an argument to cd
exists in the current directory.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

A non-interactive shell exits with an error status if a variable
assignment error occurs when no command name follows the assignment
statements. A variable assignment error occurs, for example, when trying
to assign a value to a readonly variable.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

A non-interactive shell exits with an error status if the iteration
variable in a for statement or the selection variable in a select
statement is a readonly variable.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Process substitution is not available.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Assignment statements preceding POSIX 1003.2 special builtins persist in
the shell environment after the builtin completes.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Assignment statements preceding shell function calls persist in the
shell environment after the function returns, as if a POSIX special
builtin command had been executed.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The export and readonly builtin commands display their output in the
format required by POSIX 1003.2.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The trap builtin displays signal names without the leading SIG.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

The . and source builtins do not search the current directory for the
filename argument if it is not found by searching PATH.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

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.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

Alias expansion is always enabled, even in non-interactive shells.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

When the set builtin is invoked without options, it does not display
shell function names and definitions.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

When the set builtin is invoked without options, it displays variable
values without quotes, unless they contain shell metacharacters, even if
the result contains nonprinting characters.

%
Bash Shell - Bash POSIX Mode

Changed when 'POSIX mode' is in effect:

When the cd builtin is invoked in logical mode, and the pathname
constructed from $PWD and the directory name supplied as an argument
does not refer to an existing directory, cd will fail instead of falling
back to physical mode.

%
Bash Shell - Bash POSIX Mode

POSIX 1003.2 behavior not implemented by bash:

Assignment statements affect the execution environment of all builtins,
not just special ones.

%
Bash Shell - Bash POSIX Mode

POSIX 1003.2 behavior not implemented by bash:

When a subshell is created to execute a shell script with execute
permission, but without a leading `#!', Bash sets $0 to the full
pathname of the script as found by searching $PATH, rather than the
command as typed by the user.

%
Bash Shell - Bash POSIX Mode

POSIX 1003.2 behavior not implemented by bash:

When using `.' to source a shell script found in $PATH, bash checks
execute permission bits rather than read permission bits, just as if it
were searching for a command.

%
Bash Shell - Job Control Basics

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 system's terminal driver and Bash.

%
Bash Shell - Job Control Basics

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, 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.

%
Bash Shell - Job Control Basics

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.

%
Bash Shell - Job Control Basics

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 write to the
terminal. Background processes which attempt to read from (write to) the
terminal are sent a SIGTTIN (SIGTTOU) signal by the terminal driver,
which, unless caught, suspends the process.

%
Bash Shell - Job Control Basics

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 then manipulates the state of this job,
using the bg command to continue it in the background, the fg command to
continue it in the foreground, or the kill command to kill it. A `^Z'
takes effect immediately, and has the additional side effect of causing
pending output and typeahead to be discarded.

%
Bash Shell - Job Control Basics

There are a number of ways to refer to a job in the shell. The character
`%' introduces a job name.

%
Bash Shell - Job Control Basics

Job number n may be referred to as `%n'. 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 `%-'. 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 `-'.

%
Bash Shell - Job Control Basics

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. Using `%?ce', on the other hand,
refers to any job containing the string `ce' in its command line.

If the prefix or substring matches more than one job, Bash reports an
error.

%
Bash Shell - Job Control Basics

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'

%
Bash Shell - Job Control Basics

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 is enabled, Bash reports such changes
immediately. Any trap on SIGCHLD is executed for each child process that
exits.

%
Bash Shell - Job Control Basics

If an attempt to exit Bash is while jobs are stopped, the shell prints a
message warning that there are stopped jobs. The jobs command may then
be used to inspect their status. If a second attempt to exit is made
without an intervening command, Bash does not print another warning, and
the stopped jobs are terminated.

%
Bash Shell - Job Control Builtins

  bg
  bg [jobspec]

Resume the suspended job jobspec in the background, as if it had been
started with `&'. If jobspec is not supplied, the current job is used.
The return status is zero unless it is run when job control is not
enabled, or, when run with job control enabled, if jobspec was not found
or jobspec specifies a job that was started without job control.

%
Bash Shell - Job Control Builtins

  fg
  fg [jobspec]

Resume the job jobspec in the foreground and make it the current job. If
jobspec is not supplied, the current job is used. The return status is
that of the command placed into the foreground, or non-zero if run when
job control is disabled or, when run with job control enabled, jobspec
does not specify a valid job or jobspec specifies a job that was started
without job control.

%
Bash Shell - Job Control Builtins - jobs

  jobs
  jobs [-lnprs] [jobspec]jobs -x command [arguments]

-l

List process IDs in addition to the normal information.

%
Bash Shell - Job Control Builtins - jobs

  jobs
  jobs [-lnprs] [jobspec]jobs -x command [arguments]

-n

Display information only about jobs that have changed status since the
user was last notified of their status.

%
Bash Shell - Job Control Builtins - jobs

  jobs
  jobs [-lnprs] [jobspec]jobs -x command [arguments]

-p

List only the process ID of the job's process group leader.

%
Bash Shell - Job Control Builtins - jobs

  jobs
  jobs [-lnprs] [jobspec]jobs -x command [arguments]

-r

Restrict output to running jobs.

%
Bash Shell - Job Control Builtins - jobs

  jobs
  jobs [-lnprs] [jobspec]jobs -x command [arguments]

-s

Restrict output to stopped jobs.

%
Bash Shell - Job Control Builtins - jobs

  jobs
  jobs [-lnprs] [jobspec]jobs -x command [arguments]

If jobspec is given, output is restricted to information about that job.
If jobspec is not supplied, the status of all jobs is listed.

%
Bash Shell - Job Control Builtins - jobs

  jobs
  jobs [-lnprs] [jobspec]jobs -x command [arguments]

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

%
Bash Shell - Job Control Builtins - kill

  kill [-s sigspec] [-n signum] [-sigspec] jobspec or pid
  kill -l [exit_status]

Send a signal specified by sigspec or signum to the process named by job
specification jobspec or process ID pid. sigspec is either a signal name
such as SIGINT (with or without the SIG prefix) or a signal number;
signum is a signal number. If sigspec and signum are not present,
SIGTERM is used. The `-l' option 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
zero. exit_status is a number specifying a signal number or the exit
status of a process terminated by a signal.

%
Bash Shell - Job Control Builtins - kill

  kill [-s sigspec] [-n signum] [-sigspec] jobspec or pid
  kill -l [exit_status]

The return status is zero if at least one signal was successfully sent,
or non-zero if an error occurs or an invalid option is encountered. wait

%
Bash Shell - Job Control Builtins

  wait [jobspec or pid]

Wait until the child process specified by process ID pid or job
specification jobspec exits and return the exit status of the last
command waited for. If a job spec is given, all processes in the job are
waited for. If no arguments are given, all currently active child
processes are waited for, and the return status is zero. If neither
jobspec nor pid specifies an active child process of the shell, the
return status is 127. 

%
Bash Shell - Job Control Builtins

  disown
  disown [-ar] [-h] [jobspec...]

Without options, each jobspec is removed from the table of active jobs.
If the `-h' option is given, the job 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 jobspec is not present, and neither the `-a' nor `-r' option
is supplied, the current job is used. If no jobspec is supplied, the
`-a' option means to remove or mark all jobs; the `-r' option without a
jobspec argument restricts operation to running jobs.

%
Bash Shell - Job Control Builtins

  suspend
  suspend [-f]

Suspend the execution of this shell until it receives a SIGCONT signal.
The `-f' option means to suspend even if the shell is a login shell.

When job control is not active, the kill and wait builtins do not accept
jobspec arguments.  They must be supplied process IDs.

%
Bash Shell - Job Control Variables

auto_resume

This variable controls how the shell interacts with the user and job
control. If this variable exists then single word simple commands
without redirections are treated as candidates for resumption of an
existing job. There is no ambiguity allowed; if there is more than one
job beginning with the string typed, then the most recently accessed job
will be selected. The name of a stopped job, in this context, is the
command line used to start it. If this variable is 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 ID. 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 `%' job ID.

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Bash Shell - Command Line Editing

  C-b

Move back one character.

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Bash Shell - Command Line Editing

  C-f

Move forward one character.

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Bash Shell - Command Line Editing

  DEL or Backspace

Delete the character to the left of the cursor.

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Bash Shell - Command Line Editing

  C-d

Delete the character underneath the cursor.

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Bash Shell - Command Line Editing

  Printing characters

Insert the character into the line at the cursor.

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Bash Shell - Command Line Editing

  C-_ or C-x C-u

Undo the last editing command. You can undo all
the way back to an empty line. (Depending on your configuration, the
Backspace key be set to delete the character to the left of the cursor
and the DEL key set to delete the character underneath the cursor, like
C-d, rather than the character to the left of the cursor.)

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Bash Shell - Command Line Editing

  C-a

Move to the start of the line.

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Bash Shell - Command Line Editing

  C-e

Move to the end of the line.

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Bash Shell - Command Line Editing

  M-f

Move forward a word, where a word is composed of letters and digits.

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Bash Shell - Command Line Editing

  M-b

Move backward a word.

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Bash Shell - Command Line Editing

  C-l

Clear the screen, reprinting the current line at the top.

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Bash Shell - Command Line Editing

  C-k

Kill the text from the current cursor position to the end of the line.

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Bash Shell - Command Line Editing

  M-d

Kill from the cursor 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 M-f.

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Bash Shell - Command Line Editing

  M-DEL

Kill from the cursor the start of the current word, or, if between
words, to the start of the previous word. Word boundaries are the same
as those used by M-b.

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Bash Shell - Command Line Editing

  C-w

Kill from the cursor to the previous whitespace. This is different than
M-DEL because the word boundaries differ.

Here is how to yank the text back into the line. Yanking means to copy
the most-recently-killed text from the kill buffer.

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Bash Shell - Command Line Editing

  C-y

Yank the most recently killed text back into the buffer at the cursor.

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Bash Shell - Command Line Editing

  M-y

Rotate the kill-ring, and yank the new top. You can only do this if the
prior command is

  C-y or M-y.

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Bash Shell - Readline Arguments

You can pass numeric arguments to Readline commands. Sometimes the
argument acts as a repeat count, other times it is the sign of the
argument that is significant. If you pass a negative argument to a
command which normally acts in a forward direction, that command will
act in a backward direction. For example, to kill text back to the start
of the line, you might type `M--C-k'.

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Bash Shell - Readline Arguments

The general way to pass numeric arguments to a command is to type meta
digits before the command. If the first `digit' typed is a minus sign
(`-'), then the sign of the argument will be negative. Once you have
typed one meta digit to get the argument started, you can type the
remainder of the digits, and then the command. For example, to give the
C-d command an argument of 10, you could type `M-1 0 C-d', which will
delete the next ten characters on the input line.

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Bash Shell - Searching for Commands in the History

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

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Bash Shell - Searching for Commands in the History

Incremental history 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. To search backward in the
history for a particular string, type C- r. Typing C-s searches forward
through the history. 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 ESC and C-J
characters will terminate an incremental search.

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Bash Shell - Searching for Commands in the History

C-g will abort an incremental history search and restore the original
line. When the search is terminated, the history entry containing the
search string becomes the current line.

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Bash Shell - Searching for Commands in the History

To find other matching entries in the history list, type C-r or C-s as
appropriate. This will search backward or forward in the history for the
next entry matching the search string typed so far.

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Bash Shell - Searching for Commands in the History

Any other key sequence bound to a Readline command will terminate the
search and execute that command. For instance, a RET will terminate the
search and accept the line, thereby executing the command from the
history list. A movement command will terminate the search, make the
last line found the current line, and begin editing.

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Bash Shell - Searching for Commands in the History

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

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Bash Shell - Searching for Commands in the History

Non-incremental history 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.

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Bash Shell - Readline Init File

Although the Readline library comes with a set of Emacs-like keybindings
installed by default, it is possible to use a different set of
keybindings. Any user can customize programs that use

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Bash Shell - Readline Init File - ~/.inputrc

Readline by putting commands in an inputrc file, conventionally in his
home directory. The name of this file is taken from the value of the
shell variable INPUTRC. If that variable is unset, the default is
`~/.inputrc'.

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Bash Shell - Readline Init File - ~/.inputrc

When a program which uses the Readline library starts up, the init file
is read, and the key bindings are set.

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Bash Shell - Readline Init File - ~/.inputrc

In addition, the C-x C-r command re-reads the init file, thus
incorporating any changes that you might have made to it. 

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Bash Shell - Readline Init File Syntax - ~/.inputrc

Lines beginning with a `#' are comments. Lines beginning with a `$'
indicate conditional constructs. Other lines denote variable settings
and key bindings. Variable Settings

You can modify the run-time behavior of Readline by altering the values
of variables in Readline using the set command within the init file.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  set variable value

Here, for example, is how to change from the default Emacs-like key
binding to use vi  line editing commands: 
 
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Bash Shell - Readline Init File Syntax - ~/.inputrc

  set editing-mode vi

Variable names and values, where appropriate, are recognized without
regard to case.

The bind -V command lists the current Readline variable names and
values.

A great deal of run-time behavior is changeable with the following
variables. 

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  bell-style

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'
(the default), Readline attempts to ring the terminal's bell.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  comment-begin

The string to insert at the beginning of the line when the
insert-comment command is executed. The default value is "#".

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  completion-ignore-case

If set to `on', Readline performs filename matching and completion in a
case- insensitive fashion. The default value is `off'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  completion-query-items

The number of possible completions that determines when the user is
asked whether he wants to see the list of possibilities. If the number
of possible completions is greater than this value, Readline will ask
the user whether or not he wishes to view them; otherwise, they are
simply listed. This variable must be set to an integer value greater
than or equal to 0. The default limit is 100. 

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  convert-meta

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
ESC character, converting them to a meta-prefixed key sequence. The
default value is `on'. 

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  disable-completion

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. The default is `off'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  editing-mode

The editing-mode variable controls which default set of key bindings is
used. By default, Readline starts up in Emacs editing mode, where the
keystrokes are most similar to Emacs. This variable can be set to either
`emacs' or `vi'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  enable-keypad

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. The default is `off'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  expand-tilde

If set to `on', tilde expansion is performed when Readline attempts word
completion.

The default is `off'.

If set to `on', the history code attempts to place point at the same
location on each history line retrived with previous-history or
next-history.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  horizontal-scroll-mode

This variable can be set to either `on' or `off'. Setting it to `on'
means that the text of the lines being edited will scroll horizontally
on a single screen line when they are longer than the width of the
screen, instead of wrapping onto a new screen line. By default, this
variable is set to `off'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  input-meta

If set to `on', Readline will enable eight-bit input (it will not clear
the eighth bit in the characters it reads), regardless of what the
terminal claims it can support. The default value is `off'. The name
meta-flag is a synonym for this variable.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  isearch-terminators

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.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  keymap

Sets Readline's idea of the current keymap for key binding commands.
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. The default value is
emacs. The value of the editing-mode variable also affects the default
keymap.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  mark-directories

If set to `on', completed directory names have a slash appended. The
default is `on'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  mark-modified-lines

This variable, when set to `on', causes Readline to display an asterisk
(`*') at the start of history lines which have been modified. This
variable is `off' by default.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  mark-symlinked-directories

If set to `on', completed names which are symbolic links to directories
have a slash appended (subject to the value of mark-directories). The
default is `off'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  match-hidden-files

This variable, when set to `on', causes Readline to match files whose
names begin with a `.' (hidden files) when performing filename
completion, unless the leading `.' is supplied by the user in the
filename to be completed. This variable is `on' by default.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  output-meta

If set to `on', Readline will display characters with the eighth bit set
directly rather than as a meta-prefixed escape sequence. The default is
`off'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  page-completions

If set to `on', Readline uses an internal more-like pager to display a
screenful of possible completions at a time. This variable is `on' by
default.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  print-completions-horizontally

If set to `on', Readline will display completions with matches sorted
horizontally in alphabetical order, rather than down the screen. The
default is `off'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  show-all-if-ambiguous

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. The
default value is `off'.

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Bash Shell - Readline Init File Syntax - ~/.inputrc

  visible-stats

If set to `on', a character denoting a file's type is appended to the
filename when listing possible completions. The default is `off'.

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Bash Shell - Key Bindings

The syntax for controlling key bindings in the init file is simple.
First you need to find the name of the command that you want to change.
Once you know the name of the command, simply place on a line in the
init file the name of the key you wish to bind the command to, a colon,
and then the name of the command. The name of the key can be expressed
in different ways, depending on what you find most comfortable.

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Bash Shell - Key Bindings

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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Bash Shell - Key Bindings

The bind -p command displays Readline function names and bindings in a
format that can put directly into an initialization file. 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).

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Bash Shell - Key Bindings

A number of symbolic character names are recognized while processing
this key binding syntax: DEL, ESC, ESCAPE, LFD, NEWLINE, RET, RETURN,
RUBOUT, SPACE, SPC, and TAB.

  "keyseq": function-name or macro

keyseq differs from keyname above in that strings denoting an entire key
sequence can be specified, by placing the key sequence in double quotes.
Some GNU Emacs style key escapes can be used, as in the following
example, but the special character names are not recognized.

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

In the above example, C-u is again bound to the function
universal-argument (just as it was in the first example), `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'.

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Bash Shell - Key Bindings - escape sequences

  \C-

control prefix

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Bash Shell - Key Bindings - escape sequences

  \M-

meta prefix

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Bash Shell - Key Bindings - escape sequences

  \e

an escape character

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Bash Shell - Key Bindings - escape sequences

  \\

backslash

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Bash Shell - Key Bindings - escape sequences

  \"

", a double quotation mark

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Bash Shell - Key Bindings - escape sequences

  \'

', a single quote or apostrophe

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Bash Shell - Key Bindings - escape sequences

  \a

alert (bell)

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Bash Shell - Key Bindings - escape sequences

  \b

backspace

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Bash Shell - Key Bindings - escape sequences

  \d

delete

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Bash Shell - Key Bindings - escape sequences

  \f

form feed

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Bash Shell - Key Bindings - escape sequences

  \n

newline

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Bash Shell - Key Bindings - escape sequences

  \r

carriage return

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Bash Shell - Key Bindings - escape sequences

  \t

horizontal tab

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Bash Shell - Key Bindings - escape sequences

  \v

vertical tab

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Bash Shell - Key Bindings - escape sequences

  \nnn

the eight-bit character whose value is the octal value nnn (one to three
digits)

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Bash Shell - Key Bindings - escape sequences

  \xHH

the eight-bit character whose value is the hexadecimal value HH (one or
two hex digits)

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Bash Shell - Key Bindings - escape sequences

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 `''. For example, the following binding will
make `C-x \' insert a single `\' into the line:

  "\C-x\\": "\\"

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Bash Shell - Conditional Init Constructs

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

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Bash Shell - Conditional Init Constructs

  $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.

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Bash Shell - Conditional Init Constructs

  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.

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Bash Shell - Conditional Init Constructs

  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 both the
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.

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Bash Shell - Conditional Init Constructs

  application

The application construct is used to include application-specific
settings. Each program using the Readline library sets the application
name, and you can test for a particular value. This could be used to
bind key sequences to functions useful for a specific program. 

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Bash Shell - Conditional Init Constructs

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. 

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Bash Shell - Conditional Init Constructs

  $include 

This directive takes a single filename as an argument and reads commands
and bindings  from that file. For example, the following directive reads
from `/etc/inputrc': 
 
$include /etc/inputrc
 
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Bash Shell - Command Line Editing - Commands For Moving

  beginning-of-line (C-a)

Move to the start of the current line.

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Bash Shell - Command Line Editing - Commands For Moving

  end-of-line (C-e)

Move to the end of the line.

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Bash Shell - Command Line Editing - Commands For Moving

  forward-char (C-f)

Move forward a character.

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Bash Shell - Command Line Editing - Commands For Moving

  backward-char (C-b)

Move back a character.

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Bash Shell - Command Line Editing - Commands For Moving

  forward-word (M-f)

Move forward to the end of the next word. Words are composed of letters
and digits.

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Bash Shell - Command Line Editing - Commands For Moving

  backward-word (M-b)

Move back to the start of the current or previous word. Words are
composed of letters and digits.

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Bash Shell - Command Line Editing - Commands For Moving

  clear-screen (C-l)

Clear the screen and redraw the current line, leaving the current line
at the top of the screen.

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Bash Shell - Command Line Editing - Commands For Moving

  redraw-current-line ()

Refresh the current line. By default, this is unbound.

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Bash Shell - Command Line Editing - Manipulating the History

  accept-line (Newline or 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 setting of the
HISTCONTROL and HISTIGNORE variables. If this line is a modified history
line, then restore the history line to its original state.

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Bash Shell - Command Line Editing - Manipulating the History

  previous-history (C-p)

Move `back' through the history list, fetching the previous command.

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Bash Shell - Command Line Editing - Manipulating the History

  next-history (C-n)

Move `forward' through the history list, fetching the next command.

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Bash Shell - Command Line Editing - Manipulating the History

  beginning-of-history (M-<)

Move to the first line in the history.

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Bash Shell - Command Line Editing - Manipulating the History

  end-of-history (M->)

Move to the end of the input history, i.e., the line currently being
entered.

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Bash Shell - Command Line Editing - Manipulating the History

  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.

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Bash Shell - Command Line Editing - Manipulating the History

  forward-search-history (C-s)

Search forward starting at the current line and moving `down' through
the the history as necessary. This is an incremental search.

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Bash Shell - Command Line Editing - Manipulating the History

  non-incremental-reverse-search-history (M-p)

Search backward starting at the current line and moving `up' through the
history as necessary using a non-incremental search for a string
supplied by the user.

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Bash Shell - Command Line Editing - Manipulating the History

  non-incremental-forward-search-history (M-n)

Search forward starting at the current line and moving `down' through
the the history as necessary using a non-incremental search for a string
supplied by the user.

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Bash Shell - Command Line Editing - Manipulating the History

  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. By default, this command is unbound.

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Bash Shell - Command Line Editing - Manipulating the History

  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. By default, this command is unbound.

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Bash Shell - Command Line Editing - Manipulating the History

  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.

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Bash Shell - Command Line Editing - Manipulating the History

  yank-last-arg (M-. or M-_)

Insert last argument to the previous command (the last word of the
previous history entry). With an argument, behave exactly like
yank-nth-arg. Successive calls to yank-last-arg move back through the
history list, inserting the last argument of each line in turn.

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Bash Shell - Command Line Editing - Commands For Changing Text

  delete-char (C-d)

Delete the character at point. If point is at the beginning of the line,
there are no characters in the line, and the last character typed was
not bound to delete-char, then return EOF.

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Bash Shell - Command Line Editing - Commands For Changing Text

  backward-delete-char (Rubout)

Delete the character behind the cursor. A numeric argument means to kill
the characters instead of deleting them.

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Bash Shell - Command Line Editing - Commands For Changing Text

  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.
By default, this is not bound to a key.

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Bash Shell - Command Line Editing - Commands For Changing Text

  quoted-insert (C-q or C-v)

Add the next character typed to the line verbatim. This is how to insert
key sequences like C-q, for example.

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Bash Shell - Command Line Editing - Commands For Changing Text

  self-insert (a, b, A, 1, !, ...)

Insert yourself.

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Bash Shell - Command Line Editing - Commands For Changing Text

  transpose-chars (C-t)

Drag the character before the cursor forward over the character at the
cursor, moving the cursor forward as well. If the insertion point is at
the end of the line, then this transposes the last two characters of the
line. Negative arguments have no effect.

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Bash Shell - Command Line Editing - Commands For Changing Text

  transpose-words (M-t)

Drag the word before point past the word after point, moving point past
that word as well. If the insertion point is at the end of the line,
this transposes the last two words on the line.

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Bash Shell - Command Line Editing - Commands For Changing Text

  upcase-word (M-u)

Uppercase the current (or following) word. With a negative argument,
uppercase the previous word, but do not move the cursor.

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Bash Shell - Command Line Editing - Commands For Changing Text

  downcase-word (M-l)

Lowercase the current (or following) word. With a negative argument,
lowercase the previous word, but do not move the cursor.

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Bash Shell - Command Line Editing - Commands For Changing Text

  capitalize-word (M-c)

Capitalize the current (or following) word. With a negative argument,
capitalize the previous word, but do not move the cursor.

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Bash Shell - Command Line Editing - Commands For Changing Text

  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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Bash Shell - Command Line Editing - Killing And Yanking

  kill-line (C-k)

Kill the text from point to the end of the line.

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Bash Shell - Command Line Editing - Killing And Yanking

  backward-kill-line (C-x Rubout)

Kill backward to the beginning of the line.

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Bash Shell - Command Line Editing - Killing And Yanking

  unix-line-discard (C-u)

Kill backward from the cursor to the beginning of the current line.

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Bash Shell - Command Line Editing - Killing And Yanking

  kill-whole-line ()

Kill all characters on the current line, no matter where point is. By
default, this is unbound.

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Bash Shell - Command Line Editing - Killing And Yanking

  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 forward-word.

%
Bash Shell - Command Line Editing - Killing And Yanking

  backward-kill-word (M-DEL)

Kill the word behind point. Word boundaries are the same as
backward-word.

%
Bash Shell - Command Line Editing - Killing And Yanking

  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.

%
Bash Shell - Command Line Editing - Killing And Yanking

  delete-horizontal-space ()

Delete all spaces and tabs around point. By default, this is unbound.

%
Bash Shell - Command Line Editing - Killing And Yanking

  kill-region ()

Kill the text in the current region. By default, this command is
unbound.

%
Bash Shell - Command Line Editing - Killing And Yanking

  copy-region-as-kill ()

Copy the text in the region to the kill buffer, so it can be yanked
right away. By default, this command is unbound.

%
Bash Shell - Command Line Editing - Killing And Yanking

  copy-backward-word ()

Copy the word before point to the kill buffer. The word boundaries are
the same as backward-word. By default, this command is unbound.

%
Bash Shell - Command Line Editing - Killing And Yanking

  copy-forward-word ()

Copy the word following point to the kill buffer. The word boundaries
are the same as forward-word. By default, this command is unbound.

%
Bash Shell - Command Line Editing - Killing And Yanking

  yank (C-y)

Yank the top of the kill ring into the buffer at point.

%
Bash Shell - Command Line Editing - Killing And Yanking

  yank-pop (M-y)

Rotate the kill-ring, and yank the new top. You can only do this if the
prior command is yank or yank-pop.

%
Bash Shell - Command Line Editing - Specifying 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.

%
Bash Shell - Command Line Editing - Specifying Numeric Arguments

  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. By default, this is not bound to a key.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  complete (TAB)

Attempt to perform completion on the text before point. The actual
completion performed is application-specific. 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.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  possible-completions (M-?)

List the possible completions of the text before point.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  insert-completions (M-*)

Insert all completions of the text before point that would have been
generated by possible-completions.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  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.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  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.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  complete-filename (M-/)

Attempt filename completion on the text before point.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  possible-filename-completions (C-x /)

List the possible completions of the text before point, treating it as a
filename.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  complete-username (M-~)

Attempt completion on the text before point, treating it as a username.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  possible-username-completions (C-x ~)

List the possible completions of the text before point, treating it as a
username.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  complete-variable (M-$)

Attempt completion on the text before point, treating it as a shell
variable.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  possible-variable-completions (C-x $)

List the possible completions of the text before point, treating it as a
shell variable.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  complete-hostname (M-@)

Attempt completion on the text before point, treating it as a hostname.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  possible-hostname-completions (C-x @)

List the possible completions of the text before point, treating it as a
hostname.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  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.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  possible-command-completions (C-x !)

List the possible completions of the text before point, treating it as a
command name.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  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.

%
Bash Shell - Command Line Editing - Letting Readline Type For You

  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.

%
Bash Shell - Command Line Editing - Keyboard Macros

  start-kbd-macro (C-x ()

Begin saving the characters typed into the current keyboard macro.

%
Bash Shell - Command Line Editing - Keyboard Macros

  end-kbd-macro (C-x ))

Stop saving the characters typed into the current keyboard macro and
save the definition. call-last-kbd-macro (C-x e)

Re-execute the last keyboard macro defined, by making the characters in
the macro appear as if typed at the keyboard.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  abort (C-g)

Abort the current editing command and ring the terminal's bell (subject
to the setting of bell-style).

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  prefix-meta (ESC)

Metafy the next character typed. This is for keyboards without a meta
key. Typing `ESC f' is equivalent to typing M-f.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  undo (C-_ or C-x C-u)

Incremental undo, separately remembered for each line.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  revert-line (M-r)

Undo all changes made to this line. This is like executing the undo
command enough times to get back to the beginning.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  tilde-expand (M-&)

Perform tilde expansion on the current word.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  set-mark (C-@)

Set the mark to the point. If a numeric argument is supplied, the mark
is set to that position.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  insert-comment (M-#)

Without a numeric argument, the value of the 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.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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. This command is
unbound by default.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  dump-variables ()

Print all of the settable 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.
This command is unbound by default.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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. This command
is unbound by default.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  glob-complete-word (M-g)

The word before point is treated as a pattern for pathname expansion,
with an asterisk implicitly appended. This pattern is used to generate a
list of matching file names for possible completions.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  glob-expand-word (C-x *)

The word before point is treated as a pattern for pathname expansion,
and the list of matching file names is inserted, replacing the word. If
a numeric argument is supplied, a `*' is appended before pathname
expansion.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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, a `*' is appended before pathname expansion.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  display-shell-version (C-x C-v)

Display version information about the current instance of Bash.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  history-expand-line (M-^)

Perform history expansion on the current line.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  magic-space ()

Perform history expansion on the current line and insert a space.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  alias-expand-line ()

Perform alias expansion on the current line.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  history-and-alias-expand-line ()

Perform history and alias expansion on the current line.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  insert-last-argument (M-. or M-_)

A synonym for yank-last-arg.

%
Bash Shell - Command Line Editing - Some Miscellaneous Commands

  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 $FCEDIT, $EDITOR, and emacs as
the editor, in that order.

%
Bash Shell - Command Line Editing - Readline vi Mode

While the Readline library does not have a full set of vi editing
functions, it does contain enough to allow simple editing of the line.
The Readline vi mode behaves as specified in the POSIX 1003.2 standard.

%
Bash Shell - Command Line Editing - Readline vi Mode

In order to switch interactively between emacs and vi editing modes, use
the `set -o emacs' and `set -o vi' commands. The Readline default is
emacs mode.

%
Bash Shell - Command Line Editing - Readline vi Mode

When you enter a line in vi mode, you are already placed in `insertion'
mode, as if you had typed an `i'. Pressing ESC switches you into
`command' mode, where you can edit the text of the line with the
standard vi movement keys, move to previous history lines with `k' and
subsequent lines with `j', and so forth.

%
Bash Shell - Command Line Editing - 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, the programmable completion facilities are invoked.

%
Bash Shell - Command Line Editing - Programmable Completion

First, the command name is identified. 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.

%
Bash Shell - Command Line Editing - Programmable Completion

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
described above is performed.

%
Bash Shell - Command Line Editing - Programmable Completion

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.

%
Bash Shell - Command Line Editing - Programmable Completion

Any completions specified by a filename expansion pattern to the `-G'
option are generated next. The words generated by the pattern need not
match the word being completed. The

%
Bash Shell - Command Line Editing - Programmable Completion

GLOBIGNORE shell variable is not used to filter the matches, but the
FIGNORE shell variable is used.

%
Bash Shell - Command Line Editing - Programmable Completion

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, arithmetic expansion, and pathname
expansion, as described above. The results are split using the rules
described above. The results of the expansion are prefix-matched against
the word being completed, and the matching words become the possible
completions.

%
Bash Shell - Command Line Editing - Programmable Completion

After 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 and COMP_POINT variables are
assigned values as described above. If a shell function is being
invoked, the COMP_WORDS and COMP_CWORD variables are also set. When the
function or command is invoked, the first argument is the name of the
command whose arguments are being completed, the second argument is the
word being completed, and the third argument is the word preceding the
word being completed on the current command line. No filtering of the
generated completions against the word being completed is performed; the
function or command has complete freedom in generating the matches.

%
Bash Shell - Command Line Editing - Programmable Completion

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

%
Bash Shell - Command Line Editing - Programmable Completion

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.

%
Bash Shell - Command Line Editing - Programmable Completion

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.

%
Bash Shell - Command Line Editing - Programmable Completion

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.

%
Bash Shell - Command Line Editing - Programmable Completion

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.

%
Bash Shell - Command Line Editing - Programmable Completion

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

%
Bash Shell - Command Line Editing - Programmable Completion

Readline default of filename completion is disabled. If the `-o default'
option was supplied to complete when the compspec was defined,
Readline's default completion will be performed if the compspec
generates no matches.

%
Bash Shell - Command Line Editing - Programmable Completion

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.

%
Bash Shell - Programmable Completion Builtins

Two builtin commands are available to manipulate the programmable
completion facilities. compgen complete

%
Bash Shell - Programmable Completion Builtins

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.

%
Bash Shell - Programmable Completion Builtins

compgen [option] [word]

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.

%
Bash Shell - Programmable Completion Builtins

compgen [option] [word]

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

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [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.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

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

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

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.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -o comp-option

The comp-option controls several aspects of the compspec's behavior
beyond the simple generation of completions.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -o default

Use Readline's default filename completion if the compspec generates no
matches.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -o dirnames

Perform directory name completion if the compspec generates no matches.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -o filenames

Tell Readline that the compspec generates filenames, so it can perform
any filename\- specific processing (like adding a slash to directory
names or suppressing trailing spaces). This option is intended to be
used with shell functions specified with `-F'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -o nospace

Tell Readline not to append a space (the default) to words completed at
the end of the line.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A alias

Alias names. May also be specified as `-a'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A arrayvar

Array variable names.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A binding

Readline key binding names.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A builtin

Names of shell builtin commands. May also be specified as `-b'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A command

Command names. May also be specified as `-c'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A directory

Directory names. May also be specified as `-d'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A disabled

Names of disabled shell builtins.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A enabled

Names of enabled shell builtins.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A export

Names of exported shell variables. May also be specified as `-e'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A file

File names. May also be specified as `-f'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A function

Names of shell functions.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A group

Group names. May also be specified as `-g'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A helptopic

Help topics as accepted by the help builtin.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A hostname

Hostnames, as taken from the file specified by the HOSTFILE shell
variable.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A job

Job names, if job control is active. May also be specified as `-j'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A keyword

Shell reserved words. May also be specified as `-k'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A running

Names of running jobs, if job control is active.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A service

Service names. May also be specified as `-s'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A setopt

Valid arguments for the `-o' option to the set builtin.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A shopt

Shell option names as accepted by the shopt builtin.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A signal

Signal names.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A stopped

Names of stopped jobs, if job control is active.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A user

User names. May also be specified as `-u'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -A variable

Names of all shell variables. May also be specified as `-v'.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -G globpat

The filename expansion pattern globpat is expanded to generate the
possible completions.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -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.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -C command

command is executed in a subshell environment, and its output is used as
the possible completions.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -F function

The shell function function is executed in the current shell
environment. When it finishes, the possible completions are retrieved
from the value of the COMPREPLY array variable.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -X filterpat

filterpat is a pattern as used for filename 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.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -P prefix

prefix is added at the beginning of each possible completion after all
other options have been applied.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

  -S suffix

suffix is appended to each possible completion after all other options
have been applied.

%
Bash Shell - Programmable Completion Builtins

complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] 
         [-W wordlist][-P prefix] [-S suffix] [-X filterpat] 
         [-F function][-C command] name [name ...]

complete -pr [name ...]

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.

%
Bash Shell - Bash History Facilities

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 shell 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 but after history
expansion is performed, subject to the values of the shell variables
HISTIGNORE and HISTCONTROL.

%
Bash Shell - Bash History Facilities

When the shell starts up, the history is initialized from the file named
by the HISTFILE variable (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 the HISTFILESIZE
variable. When an interactive shell exits, the last $HISTSIZE lines are
copied from the history list to the file named by $HISTFILE. If the
histappend shell option is set, 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. After
saving the history, the history file is truncated to contain no more
than $HISTFILESIZE lines. If HISTFILESIZE is not set, no truncation is
performed.

%
Bash Shell - Bash History Facilities

The builtin command fc may be used to list or edit and re-execute a
portion of the history list.

%
Bash Shell - Bash History Facilities

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.

%
Bash Shell - Bash History Facilities

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. The shopt builtin is used to set these options.

%
Bash Shell - Bash History Builtins

  fc [-e ename] [-nlr] [first] [last]
  fc -s [pat=rep] [command]

Fix Command. In the first form, a range of commands from first to last
is selected from the history list. Both first and last may be specified
as a string (to locate the most recent 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 first. If first is not specified it is set to
the previous command for editing and -16 for listing. If the `-l' flag
is given, the commands are listed on standard output. The `-n' flag
suppresses the command numbers when listing. The `-r' flag reverses the
order of the listing. Otherwise, the editor given by ename is invoked on
a file containing those commands. If ename is not given, the value of
the following variable expansion is used: ${FCEDIT:-${EDITOR:-vi}}. This
says to use the value of the FCEDIT variable if set, or the value of the
EDITOR variable if that is set, or vi if neither is set. When editing is
complete, the edited commands are echoed and executed.

%
Bash Shell - Bash History Builtins

  fc [-e ename] [-nlr] [first] [last]
  fc -s [pat=rep] [command]

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

%
Bash Shell - Bash History Builtins

  fc [-e ename] [-nlr] [first] [last]
  fc -s [pat=rep] [command]

A useful alias to use with the fc command is r='fc -s', so that typing
`r cc' runs the last command beginning with cc and typing `r'
re-executes the last command. 

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

With no options, display the history list with line numbers. Lines
prefixed with a `*' have been modified. An argument of n lists only the
last n lines. Options, if supplied, have the following meanings:

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

-c

Clear the history list. This may be combined with the other options to
replace the history list completely.

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

-d offset

Delete the history entry at position offset. offset should be specified
as it appears when the history is displayed.

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

-a

Append the new history lines (history lines entered since the beginning
of the current Bash session) to the history file.

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

-n

Append the history lines not already read from the history file to the
current history list.

These are lines appended to the history file since the beginning of the
current Bash session.

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

-r

Read the current history file and append its contents to the history
list.

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

-w

Write out the current history to the history file.

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

-p

Perform history substitution on the args and display the result on the
standard output, without storing the results in the history list.

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

-s

The args are added to the end of the history list as a single entry.

%
Bash Shell - Bash History Builtins

  history [n]
  history -c
  history -d offset
  history [-anrw] [filename]
  history -ps arg

When any of the `-w', `-r', `-a', or `-n' options is used, if filename
is given, then it is used as the history file. If not, then the value of
the HISTFILE variable is used.

%
Bash Shell - History Expansion

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.

%
Bash Shell - History Expansion

History expansion takes place in two parts. The first is to determine
which line from the history list should be used during substitution. The
second is to select portions of that line for inclusion into the current
one. The line selected from the history is called the event, and the
portions of that line that are acted upon are called words. Various
modifiers are available to manipulate the selected words. The line is
broken into words in the same fashion that Bash does, so that several
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 `\' and `'' may be used to escape the
history expansion character.

%
Bash Shell - History 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, 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 expansion 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. This is most useful in conjunction
with Readline.

%
Bash Shell - History Expansion

The shell allows control of the various characters used by the history
expansion mechanism with the histchars variable.

%
Bash Shell - Event Designators

  !

Start a history substitution, except when followed by a space, tab, the
end of the line, `=' or `('.

%
Bash Shell - Event Designators

  !n

Refer to command line n.

%
Bash Shell - Event Designators

  !-n

Refer to the command n lines back.

%
Bash Shell - Event Designators

  !!

Refer to the previous command. This is a synonym for `!-1'.

%
Bash Shell - Event Designators

  !string

Refer to the most recent command starting with string.

%
Bash Shell - Event Designators

  !?string[?]

Refer to the most recent command containing string. The trailing `?' may
be omitted if the string is followed immediately by a newline.

%
Bash Shell - Event Designators

  ^string1^string2^

Quick Substitution. Repeat the last command, replacing string1 with
string2.

Equivalent to !!:s/string1/string2/.

%
Bash Shell - Event Designators

  !#

The entire command line typed so far.

%
Bash Shell - Word Designators

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

    !!

designates the preceding command. When you type this, the preceding
command is repeated in toto.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  !!:$

designates the last argument of the preceding command. This may be
shortened to !$.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  !fi:2

designates the second argument of the most recent command starting with
the letters fi.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  0 (zero)

The 0th word. For many applications, this is the command word.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  n

The nth word.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  ^

The first argument; that is, word 1.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  $

The last argument.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  %

The word matched by the most recent `?string?' search.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  x-y

A range of words; `-y' abbreviates `0-y'.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  *

All of the words, except the 0th. 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.

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  x*

Abbreviates `x-$'

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

%
Bash Shell - Word Designators

Word designators are used to select desired words from the history
event. A `:' separates the event specification from the word designator.

  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.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  h

Remove a trailing pathname component, leaving only the head.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  t

Remove all leading pathname components, leaving the tail.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  r

Remove a trailing suffix of the form `.suffix', leaving the basename.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  e

Remove all but the trailing suffix.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  p

Print the new command but do not execute it.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  q

Quote the substituted words, escaping further substitutions.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  x

Quote the substituted words as with `q', but break into words at spaces,
tabs, and newlines.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  s/old/new/

Substitute new for the first occurrence of old in the event line. Any
delimiter may be used in place of `/'. 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 `&'. The final
delimiter is optional if it is the last character on the input line.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  &

Repeat the previous substitution.

%
Bash Shell - History Word Modifiers

After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.

  g

Cause changes to be applied over the entire event line. Used in
conjunction with `s', as in gs/old/new/, or with `&'.

%
Bash Shell - Major Differences From The Bourne

Bash implements essentially the same grammar, parameter and variable
expansion, redirection, and quoting as the Bourne Shell. Bash uses the
POSIX 1003.2 standard as the specification of how these features are to
be implemented.

%
Bash Shell - Major Differences From The Bourne

  * Bash is POSIX-conformant, even where the POSIX specification differs
    from traditional sh behavior.

%
Bash Shell - Major Differences From The Bourne

  * Bash has multi-character invocation options.

%
Bash Shell - Major Differences From The Bourne

  * Bash has command-line editing
    and the bind builtin.

%
Bash Shell - Major Differences From The Bourne

  * Bash provides a programmable word completion mechanism, and two
builtin commands, complete and
    compgen, to manipulate it.

%
Bash Shell - Major Differences From The Bourne

  * Bash has command history and
    the history and fc builtins to manipulate it.

%
Bash Shell - Major Differences From The Bourne

  * Bash implements csh-like history expansion.

%
Bash Shell - Major Differences From The Bourne

  * Bash has one-dimensional array variables, and
    the appropriate variable expansions and assignment syntax to use them.
    Several of the Bash builtins take options to act on arrays. Bash
    provides a number of built-in array variables.

%
Bash Shell - Major Differences From The Bourne

  * The $'...' quoting syntax, which expands ANSI-C backslash-escaped
    characters in the text between the single quotes, is supported.

%
Bash Shell - Major Differences From The Bourne

  * Bash supports the $"..." quoting syntax to do locale-specific
    translation of the characters between the double quotes. The `-D',
    `--dump-strings', and `- -dump-po-strings' invocation options list the
    translatable strings found in a script.

%
Bash Shell - Major Differences From The Bourne

  * Bash implements the ! keyword to negate the return value of a pipeline
   . Very useful when an if statement needs to
    act only if a test fails.

%
Bash Shell - Major Differences From The Bourne

  * Bash has the time reserved word and command timing.  The display of
the timing statistics may be controlled 
    with the TIMEFORMAT variable.

%
Bash Shell - Major Differences From The Bourne

  * Bash implements the for (( expr1 ; expr2 ; expr3 )) arithmetic for
    command, similar to the C language.

%
Bash Shell - Major Differences From The Bourne

  * Bash includes the select compound command, which allows the generation
    of simple menus.

%
Bash Shell - Major Differences From The Bourne

  * Bash includes the [[ compound command, which makes conditional testing
    part of the shell grammar.

%
Bash Shell - Major Differences From The Bourne

  * Bash includes brace expansion and
    tilde expansion.

%
Bash Shell - Major Differences From The Bourne

  * Bash implements command aliases and the alias and unalias builtins
   .

%
Bash Shell - Major Differences From The Bourne

  * Bash provides shell arithmetic, the (( compound command, and
arithmetic expansion.

%
Bash Shell - Major Differences From The Bourne

  * Variables present in the shell's initial environment are automatically
    exported to child processes. The Bourne shell does not normally do this
    unless the variables are explicitly marked using the export command.

%
Bash Shell - Major Differences From The Bourne

  * Bash includes the POSIX pattern removal `%', `#', `%%' and `##'
    expansions to remove leading or trailing substrings from variable values
   .

%
Bash Shell - Major Differences From The Bourne

  * The expansion ${#xx}, which returns the length of ${xx}, is supported
   .

%
Bash Shell - Major Differences From The Bourne

  * The expansion ${var:offset[:length]}, which expands to the substring
    of var's value of length length, beginning at offset, is present.

%
Bash Shell - Major Differences From The Bourne

  * The expansion ${var/[/]pattern[/replacement]}, which matches pattern
    and replaces it with replacement in the value of var, is available

%
Bash Shell - Major Differences From The Bourne

  * The expansion ${!prefix}* expansion, which expands to the names of all
    shell variables whose names begin with prefix, is available.

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Bash Shell - Major Differences From The Bourne

  * Bash has indirect variable expansion using ${!word}.

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Bash Shell - Major Differences From The Bourne

  * Bash can expand positional parameters beyond $9 using ${num}.

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Bash Shell - Major Differences From The Bourne

  * The POSIX $() form of command substitution is implemented, and
preferred to the Bourne shell's "
    (which is also implemented for backwards compatibility).

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Bash Shell - Major Differences From The Bourne

  * Bash has process substitution.

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Bash Shell - Major Differences From The Bourne

  * Bash automatically assigns variables that provide information about
    the current user (UID, EUID, and GROUPS), the current host (HOSTTYPE,
    OSTYPE, MACHTYPE, and HOSTNAME), and the instance of Bash that is
    running (BASH, BASH_VERSION, and BASH_VERSINFO).

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Bash Shell - Major Differences From The Bourne

  * The IFS variable is used to split only the results of expansion, not
    all words. This closes a longstanding
    shell security hole.

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Bash Shell - Major Differences From The Bourne

  * Bash implements the full set of POSIX 1003.2 filename expansion
    operators, including character classes, equivalence classes, and
    collating symbols.

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Bash Shell - Major Differences From The Bourne

  * Bash implements extended pattern matching features when the extglob
    shell option is enabled.

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Bash Shell - Major Differences From The Bourne

  * It is possible to have a variable and a function with the same name;
    sh does not separate the two name spaces.

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Bash Shell - Major Differences From The Bourne

  * Bash functions are permitted to have local variables using the local
    builtin, and thus useful recursive functions may be written.

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Bash Shell - Major Differences From The Bourne

  * Variable assignments preceding commands affect only that command, even
    builtins and functions. In sh, all
    variable assignments preceding commands are global unless the command is
    executed from the file system.

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Bash Shell - Major Differences From The Bourne

  * Bash performs filename expansion on filenames specified as operands to
    input and output redirection operators.

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Bash Shell - Major Differences From The Bourne

  * Bash contains the `<>' redirection operator, allowing a file to be
    opened for both reading and writing, and the `&>' redirection operator,
    for directing standard output and standard error to the same file.

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Bash Shell - Major Differences From The Bourne

  * Bash treats a number of filenames specially when they are used in
    redirection operators.

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Bash Shell - Major Differences From The Bourne

  * Bash can open network connections to arbitrary machines and services
    with the redirection operators.

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Bash Shell - Major Differences From The Bourne

  * The noclobber option is available to avoid overwriting existing files
    with output redirection. The `>|'
    redirection operator may be used to override noclobber.

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Bash Shell - Major Differences From The Bourne

  * The Bash cd and pwd builtins
    each take `-L' and `-P' options to switch between logical and
physical
    modes.

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Bash Shell - Major Differences From The Bourne

  * Bash allows a function to override a builtin with the same name, and
    provides access to that builtin's functionality within the function via
    the builtin and command builtins.

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Bash Shell - Major Differences From The Bourne

  * The command builtin allows selective disabling of functions when
    command lookup is performed.

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Bash Shell - Major Differences From The Bourne

  * Individual builtins may be enabled or disabled using the enable
    builtin.

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Bash Shell - Major Differences From The Bourne

  * The Bash exec builtin takes additional options that allow users to
    control the contents of the environment passed to the executed command,
    and what the zeroth argument to the command is to be.

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Bash Shell - Major Differences From The Bourne

  * Shell functions may be exported to children via the environment using
    export -f.

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Bash Shell - Major Differences From The Bourne

  * The Bash export, readonly, and declare builtins can take a `-f' option
    to act on shell functions, a `-p' option to display variables with
    various attributes set in a format that can be used as shell input, a
    `-n' option to remove various variable attributes, and `name=value'
    arguments to set variable attributes and values simultaneously.

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Bash Shell - Major Differences From The Bourne

  * The Bash hash builtin allows a name to be associated with an arbitrary
    filename, even when that filename cannot be found by searching the
    $PATH, using `hash -p'.

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Bash Shell - Major Differences From The Bourne

  * Bash includes a help builtin for quick reference to shell facilities
   .

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Bash Shell - Major Differences From The Bourne

  * The printf builtin is available to display formatted output.

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Bash Shell - Major Differences From The Bourne

  * The Bash read builtin will
    read a line ending in `\' with the `-r' option, and will use the REPLY
    variable as a default if no non- option arguments are supplied. The Bash
    read builtin also accepts a prompt string with the `-p' option and will
    use Readline to obtain the line when given the `-e' option.

    The read builtin also has additional options to control input: the `-s'
    option will turn off echoing of input characters as they are read, the
    `-t' option will allow read to time out if input does not arrive within
    a specified number of seconds, the `-n' option will allow reading only a
    specified number of characters rather than a full line, and the `-d'
    option will read until a particular character rather than newline.

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Bash Shell - Major Differences From The Bourne

  * The return builtin may be used to abort execution of scripts executed
    with the . or source builtins. *
    Bash includes the shopt builtin, for finer control of shell optional
    capabilities, and allows these
    options to be set and unset at shell invocation.

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Bash Shell - Major Differences From The Bourne

  * Bash has much more optional behavior controllable with the set builtin
   .

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Bash Shell - Major Differences From The Bourne

  * The test builtin is slightly
    different, as it implements the POSIX algorithm, which specifies the
    behavior based on the number of arguments.

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Bash Shell - Major Differences From The Bourne

  * The trap builtin allows a
    DEBUG pseudo-signal specification, similar to EXIT. Commands specified
    with a DEBUG trap are executed after every simple command. The DEBUG
    trap is not inherited by shell functions unless the function has been
    given the trace attribute.

    The trap builtin allows an ERR
    pseudo-signal specification, similar to EXIT and DEBUG. Commands
    specified with an ERR trap are executed after a simple command fails,
    with a few exceptions. The ERR trap is not inherited by shell functions.

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Bash Shell - Major Differences From The Bourne

  * The Bash type builtin is more extensive and gives more information
    about the names it finds.

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Bash Shell - Major Differences From The Bourne

  * The Bash umask builtin permits a `-p' option to cause the output to be
    displayed in the form of a umask command that may be reused as input
   .

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Bash Shell - Major Differences From The Bourne

  * Bash implements a csh-like directory stack, and provides the pushd,
    popd, and dirs builtins to manipulate it. Bash also makes the
directory stack visible as the value of the
    DIRSTACK shell variable.

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Bash Shell - Major Differences From The Bourne

  * Bash interprets special backslash-escaped characters in the prompt
    strings when interactive.

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Bash Shell - Major Differences From The Bourne

  * Bash interprets special backslash-escaped characters in the prompt
    strings when  interactive.

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Bash Shell - Major Differences From The Bourne

  * The Bash restricted mode is more useful; The  SVR4.2 shell
    restricted mode is too limited. 

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Bash Shell - Major Differences From The Bourne

  * The disown builtin can remove a job from the internal shell job
    table or suppress the sending of SIGHUP to a job when the shell exits as
     the result of a SIGHUP. 

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Bash Shell - Major Differences From The Bourne

  * The SVR4.2 shell has two privilege-related builtins (mldmode and
    priv) not present in  Bash. 

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Bash Shell - Major Differences From The Bourne

  * Bash does not have the stop or newgrp builtins. 

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Bash Shell - Major Differences From The Bourne

  * Bash does not use the SHACCT variable or perform shell
    accounting. 

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Bash Shell - Major Differences From The Bourne

  * The SVR4.2 sh uses a TIMEOUT variable like Bash uses TMOUT. 


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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * Bash does not fork a subshell when redirecting into or out of a shell
    control structure  such as an if or while statement. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * Bash does not allow unbalanced quotes. The SVR4.2 shell will silently
    insert a needed  closing quote at EOF under certain circumstances. This
    can be the cause of some hard- to-find errors. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * The SVR4.2 shell uses a baroque memory management scheme based on
    trapping  SIGSEGV. If the shell is started from a process with SIGSEGV
    blocked (e.g., by using  the system() C library function call), it
    misbehaves badly. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * In a questionable attempt at security, the SVR4.2 shell, when invoked
    without the `- p' option, will alter its real and effective UID and GID
    if they are less than some magic  threshold value, commonly 100. This
    can lead to unexpected results. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * The SVR4.2 shell does not allow users to trap SIGSEGV, SIGALRM, or
    SIGCHLD. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * The SVR4.2 shell does not allow the IFS, MAILCHECK, PATH, PS1, or PS2
    variables to  be unset. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * The SVR4.2 shell treats `^' as the undocumented equivalent of `|'. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * Bash allows multiple option arguments when it is invoked (-x -v); the
    SVR4.2 shell  allows only one option argument (-xv). In fact, some
    versions of the shell dump core if  the second argument begins with a
    `-'. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * The SVR4.2 shell exits a script if any builtin fails; Bash exits a
    script only if one of the  POSIX 1003.2 special builtins fails, and only
    for certain failures, as enumerated in the  POSIX 1003.2 standard. 

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Bash Shell - Implementation Differences From The SVR4.2 Shell 

  * The SVR4.2 shell behaves differently when invoked as jsh (it turns on
    job control).