Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By : Richard Blum, Christine Bresnahan
Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By: Richard Blum, Christine Bresnahan

Overview of this book

The Linux command line enables you to type specific shell commands directly into the system to manipulate files and query system resources. Command line statements can be combined into short programs called shell scripts, a practice increasing in popularity due to its usefulness in automation. Linux is a robust system with tremendous potential, and Linux Command Line and Shell Scripting Bible opens the door to new possibilities. Linux Command Line and Shell Scripting Bible is your essential Linux guide. It contains new functional examples that are fully updated to align with the latest Linux features. Beginning with command line fundamentals, the book moves into shell scripting and shows you the practical application of commands in automating frequently performed functions. This book is a complete guide providing detailed instruction and expert advice working within this aspect of Linux. Whether used as a tutorial or as a quick reference, this book contains information that every Linux user should know.
Table of Contents (34 chapters)
Part I: The Linux Command Line
Part II: Shell Scripting Basics
Part III: Advanced Shell Scripting
Part IV: Creating Practical Scripts
End User License Agreement

Using Variables in Functions

You might have noticed in the test5 example in the previous section that we used a variable called $value within the function to hold the value that it processed. When you use variables in your functions, you need to be somewhat careful about how you define and handle them. This is a common cause of problems in shell scripts. This section goes over a few techniques for handling variables both inside and outside your shell script functions.

Passing parameters to a function

As mentioned earlier in the “Returning a Value” section, the bash shell treats functions just like mini-scripts. This means that you can pass parameters to a function just like a regular script (see Chapter 14).

Functions can use the standard parameter environment variables to represent any parameters passed to the function on the command line. For example, the name of the function is defined in the $0 variable, and any parameters on the function command line are defined using...