Built-in variables are special variables provided to shell by Linux that you can use to make decisions within a shell 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
#!/bin/sh#my test programecho "Number of parameters is $#"echo "Program name is $0"echo "Parameters as a single string is ...