get help while writting shell scripts

October 22nd, 2006 mysurface Posted in Bash, help, Misc | Hits: 20146 | 1 Comment »

sometimes I just forgot the syntax of using if, while or for. Sometimes I am not sure the syntax i used is it correct. Let say I wanna refers back how to use square bracket ( [ ] ), by specified

man "\[" 

It leads me to a lengthy BASH_BINUTILS manual, which cause me more headache. I discover a good command which can help me a bit better, its call help.

help [

The result I get is

[: [ arg... ]
     This is a synonym for the "test" builtin, but the last
    argument must be a literal `]', to match the opening `['.
[[ ... ]]: [[ expression ]]
     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.  The
    && and || operators do not evaluate EXPR2 if EXPR1 is sufficient to
    determine the expression's value.

Isn’t it better? If you still find it difficult, then remember to refers here : ) LBE have a category for Bash.

To get more shorter reference help, specified with -s, for example:

help -s if

This will show the result as bellow:

if: if COMMANDS; then COMMANDS; [ elif COMMANDS; then COMMANDS; ]... [ else COMMANDS; ] fi

One Response to “get help while writting shell scripts”

  1. you’ve an ideal blog right here!

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