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)
2
Part I: The Linux Command Line
13
Part II: Shell Scripting Basics
20
Part III: Advanced Shell Scripting
28
Part IV: Creating Practical Scripts
32
End User License Agreement

Practical Examples

Now that you've seen how to use the different ways to create loops in shell scripts, let's look at some practical examples of how to use them. Looping is a common way to iterate through data on the system, whether it's files in folders or data contained in a file. Here are a couple of examples that demonstrate using simple loops to work with data.

Finding executable files

When you run a program from the command line, the Linux system searches a series of folders looking for that file. Those folders are defined in the PATH environment variable. If you want to find out just what executable files are available on your system for you to use, just scan all the folders in the PATH environment variable. That may take some time to do manually, but it's a breeze working out a small shell script to do that.

The first step is to create a for loop to iterate through the folders stored in the PATH environment variable. When you do that, don't forget to...