Book Image

Learn Linux Shell Scripting – Fundamentals of Bash 4.4

By : Sebastiaan Tammer
Book Image

Learn Linux Shell Scripting – Fundamentals of Bash 4.4

By: Sebastiaan Tammer

Overview of this book

Shell scripts allow us to program commands in chains and have the system execute them as a scripted event, just like batch files. This book will start with an overview of Linux and Bash shell scripting, and then quickly deep dive into helping you set up your local environment, before introducing you to tools that are used to write shell scripts. The next set of chapters will focus on helping you understand Linux under the hood and what Bash provides the user. Soon, you will have embarked on your journey along the command line. You will now begin writing actual scripts instead of commands, and will be introduced to practical applications for scripts. The final set of chapters will deep dive into the more advanced topics in shell scripting. These advanced topics will take you from simple scripts to reusable, valuable programs that exist in the real world. The final chapter will leave you with some handy tips and tricks and, as regards the most frequently used commands, a cheat sheet containing the most interesting flags and options will also be provided. After completing this book, you should feel confident about starting your own shell scripting projects, no matter how simple or complex the task previously seemed. We aim to teach you how to script and what to consider, to complement the clear-cut patterns that you can use in your daily scripting challenges.
Table of Contents (24 chapters)
Title Page
About Packt
Contributors
Preface
Free Chapter
1
Introduction
Index

Summary


This chapter was dedicated to conditional testing and scripting loops. Since we had already discussed the if-then-else statements, we recapped on this information before going on to showing more advanced uses of the conditional testing toolkit. This advanced information included using regular expressions, which we learned about in the previous chapter, within a conditional testing scenario to allow for more flexible tests. We also showed you how multiple conditions can be tested sequentially, using elif (short for else if). We explained how multiple if-then-else statements can be nested to create advanced logic.

In the second part of this chapter, we introduced the while loop. We showed you how we can use this to create a script that will run indefinitely, or how we can use conditions to stop the loop when a certain criteria has been met. We presented the until keyword, which has the same functionality as while but allows for negative checking instead of positive for while. We ended...