Foundations Updated 2026-09 View as Markdown

Special Variables

In last tutorial about shell function, you use “$1” represent the first argument passed to functionA.

In last tutorial about shell function, you use “$1” represent the first argument passed to function_A. Moreover, here are some special variables in shell:

• $0 - The filename of the current script.

• $n - The Nth argument passed to script was invoked or function was called.

• $# - The number of argument passed to script or function.

• $@ - All arguments passed to script or function.

• $* - All arguments passed to script or function.

• $? - The exit status of the last command executed.

• $$ - The process ID of the current shell. For shell scripts, this is the process ID under which they are executing.

• $! - The process number of the last background command.

Example:#

#!/bin/bash
echo "Script Name: $0"
function func {
    for var in $*
    do
        let i=i+1
        echo "The \$${i} argument is: ${var}"
    done
    echo "Total count of arguments: $#"
}
func We are argument

$@ and $* have different behavior when they were enclosed in double quotes.

#!/bin/bash
function func {
    echo "--- \"\$*\""
    for ARG in "$*"
    do
        echo $ARG
    done

    echo "--- \"\$@\""
    for ARG in "$@"
    do
        echo $ARG
    done
}
func We are argument