conditional

Get help on Linux conditional Command.

Linux conditional command ( [ ) is use to evaluate conditional expression or execute conditional command on Linux system. The Linux conditional command is one of bash shell built in command. The command example below show how to get conditional command manual or help on Linux conditional command using shell command, this help show information on how to use the Linux conditional command, the conditional command options and the arguments that can be use with Linux conditional command.

Get Linux conditional command help [

Execute help command and the name of Linux command that we want the help file, the example below we execute help command with -m option to get the help for conditional command using the manpage format.

[linux@fedora11 ~]$ help -m [

NAME

[ - Evaluate conditional expression.

SYNOPSIS

[ arg... ]

DESCRIPTION

Evaluate conditional expression.

This is a synonym for the "test" builtin, but the last argument must

be a literal `]', to match the opening `['.

SEE ALSO

bash(1)

IMPLEMENTATION

GNU bash, version 4.0.16(1)-release (i386-redhat-linux-gnu)

License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

NAME

[[ ... ]] - Execute conditional command.

SYNOPSIS

[[ expression ]]

DESCRIPTION

Execute conditional command.

Returns a status of 0 or 1 depending on the evaluation of the conditional

expression EXPRESSION. Expressions are composed of the same primaries used

by the `test' builtin, and may be combined using the following operators:

( EXPRESSION ) Returns the value of EXPRESSION

! EXPRESSION True if EXPRESSION is false; else false

EXPR1 && EXPR2 True if both EXPR1 and EXPR2 are true; else false

EXPR1 || EXPR2 True if either EXPR1 or EXPR2 is true; else false

When the `==' and `!=' operators are used, the string to the right of

the operator is used as a pattern and pattern matching is performed.

When the `=~' operator is used, the string to the right of the operator

is matched as a regular expression.

The && and || operators do not evaluate EXPR2 if EXPR1 is sufficient to

determine the expression's value.

Exit Status:

0 or 1 depending on value of EXPRESSION.

SEE ALSO

bash(1)

IMPLEMENTATION

GNU bash, version 4.0.16(1)-release (i386-redhat-linux-gnu)

License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

[linux@fedora11 ~]$

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