Red Hat® Linux® 7 Unleashed

Built-In Variables

Built-in variables are special variables that Linux provides to you that can be used to make decisions within a program. You cannot modify the values of these variables within the shell program.

Some of these variables are

$#	Number of positional parameters passed to the shell program
$?	Completion code of the last command or shell program executed within the shell program (returned value)
$0	The name of the shell program
$*	A single string of all arguments passed at the time of invocation of the shell program

To show these built-in variables in use, here is a sample program called mypgm2:

#!/bin/sh
#my test program
echo "Number of parameters is "$#
echo "Program name is "$0
echo "Parameters as a single string is "$*

If ...