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


In this chapter, we've discussed everything parameter expansion in Bash. We started by recapping how we've used parameter substitution throughout most of this book, and how parameter substitution is only a small part of Bash parameter expansion.

We moved on to show you how we can use parameter expansion to include default values for variables, in case the user does not supply their own. This functionality also allows us to present the user with an error message if input is missing, although not in the cleanest way.

We ended this introduction to parameter expansion by showing you how we could use this to determine the length of variable values, and we showed you how we've actually used that extensively in the book already, in the form of the $# syntax.

We continued with describing parameter expansions under the heading of Variable manipulation. This includes the functionality of pattern substitution, which allows us to replace a part of the variable's value (the pattern) with another...