Builtin Variables

Built-in variables are special variables provided to shell by Linux that can be used 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 mypgm2:

#my test program echo "Number of parameters is $#" echo "program name is $0"

echo "parameters as a single string is $*"

If you execute mypgm2 from the command line in pdksh and bash as follows,

$ bash mypgm2 Sanjiv Guha you get the following result:

Number of parameters is 2 Program name is mypgm2

Parameters as a single string is Sanjiv Guha

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