Linux® Command Line and Shell Scripting Bible

Chapter 11. Handling User Input

IN THIS CHAPTER

• Using command line parameters

• Working out your options

• Getting input from users

So far you've seen how to write scripts that interact with data, variables, and files on the Linux system. Sometimes, you need to write a script that has to interact with the person running the script. The bash shell provides a few different methods for retrieving data from people, including command line parameters (data values added after the command), command line options (single-letter values that modify the behavior of the command), and reading input directly from the keyboard. This chapter discusses how to incorporate these different methods into your bash shell scripts to obtain data from the person running your script.

Command Line Parameters

The most basic method of passing data to your shell script is by using command line parameters. Command line parameters allow you to add data values to the command line when you execute the script:

$ ./addem 10 30

This example passes two command line parameters (10 and 30) to the script addem. The script handles the command line parameters using special variables. The following sections describe how to use command line parameters in your bash shell scripts.

Reading parameters

The bash shell assigns special variables, called positional parameters, to all of the parameters entered in a command line. This even includes the name of the program the shell executes. The positional parameter variables are standard numbers, with ...