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


At the start of this chapter, we explained what a variable was: a standard building block that allows us to store information, which we can reference later. We prefer to use variables for a number of reasons: we can store a value once and reference it multiple times, and if we need to change the value, we only have to change it once and the new value will be used everywhere.

We explained that a constant is a special type of variable: it is defined only once in the beginning of a script, it is not affected by user input, and it does not change during the course of the script execution.

We continued with some notes on variable naming. We demonstrated that Bash is very flexible with regard to variables: it allows many different styles of variable naming. However, we explained that readability suffers if you use multiple different naming conventions in the same script, or between multiple scripts. The best idea is to choose one way of naming variables, and stick with it. We recommended...