Positional Parameters

Positional Parameters

$0, $1, $2, etc.

Positional parameters, passed from command line to script, passed to a function, or set to a variable (see Example 4-5 and Example 15-16)

$#

Number of command-line arguments [4] or positional parameters (see Example 36-2)

$*

All of the positional parameters, seen as a single word

Note

"$*" must be quoted.
$@

Same as $*, but each parameter is a quoted string, that is, the parameters are passed on intact, without interpretation or expansion. This means, among other things, that each parameter in the argument list is seen as a separate word.

Note

Of course, "$@" should be quoted.

Other Special Parameters

$-

Flags passed to script (using set). See Example 15-16.

Caution

$!

PID (process ID) of last job run in background

$_

Special variable set to final argument of previous command executed.

$?

Exit status of a command, function, or the script itself.
$$

Process ID (PID) of the script itself. The $$ variable often finds use in scripts to construct "unique" temp file names.