List of 'if' switches anywhere?

bash if-statement switch-statement shell-exec
Danijel-James W picture Danijel-James W · Sep 29, 2013 · Viewed 28.1k times · Source

Is there a list of all the if switches for use in bash scripting? Sometimes I see someone using it and I wonder what the switch they're using actually does.

Example is the -z in this one. I know how to use it, but I don't know where it was derived from.

if [ -z "$BASH_VERSION" ]; then
    echo -e "Error: this script requires the BASH shell!"
    exit 1
fi

Any references, guides, posts, answers would be appreciated.

Answer

SheetJS picture SheetJS · Sep 29, 2013

Look at the bash manpage (man bash). The options are specified in the CONDITIONAL EXPRESSIONS section:

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

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

       -a file
              True if file exists.
       ... more options ...

It is also explained in the help:

$ help [
[: [ arg... ]
    This is a synonym for the "test" builtin, but the last
    argument must be a literal `]', to match the opening `['.

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