Arguments

Arguments are the information the user inputs upon calling a command, like rm testfile. Arguments can be passed to the script upon execution, and will modify how the script behaves.

This arguments are separated by spaces " "

From within the script we can make use of predefined variables by the system:

Predefined variables	Description
`$n`	A particular parameter passed by the user upon calling the command. "`n`" represents the parameter number.
`$*`	All of the parameters. They are represented in a single array of parameters.
`$_`	Initially, it holds the absolute path of the script or shell being invoked. However, its value changes after each command execution. Learn more
`$@`	All of the parameters. This is a list with each element being the input arguments.
`$#`	This is the number of characters inputted by the user upon calling the command.

How to use them

Here's an example on how to use the $n, $# and $* variables.

shell_script.sh

#!/bin/bash
echo The first parameter is $1
echo The number of parameters is $#
echo A list of all of the parameters: $*

user@host:~$ ./shell_script.sh parameter1 parameter2 parameter3
The first parameter is parameter1
The number of parameters is 3
A list of all of the parameters: parameter1 parameter2 parameter3