Book Image

Mastering Linux Shell Scripting - Second Edition

By : Mokhtar Ebrahim, Andrew Mallett
5 (1)
Book Image

Mastering Linux Shell Scripting - Second Edition

5 (1)
By: Mokhtar Ebrahim, Andrew Mallett

Overview of this book

In this book, you’ll discover everything you need to know to master shell scripting and make informed choices about the elements you employ. Grab your favorite editor and start writing your best Bash scripts step by step. Get to grips with the fundamentals of creating and running a script in normal mode, and in debug mode. Learn about various conditional statements' code snippets, and realize the power of repetition and loops in your shell script. You will also learn to write complex shell scripts. This book will also deep dive into file system administration, directories, and system administration like networking, process management, user authentications, and package installation and regular expressions. Towards the end of the book, you will learn how to use Python as a BASH Scripting alternative. By the end of this book, you will know shell scripts at the snap of your fingers and will be able to automate and communicate with your system with keyboard expressions.
Table of Contents (17 chapters)

Creating conditional statements using if

As we have seen so far, it is possible to build simple conditions using command-line lists. These conditional statements can be written both with and without a test. As the complexity of the tasks increases, it becomes easier to create statements using if. This will certainly ease both the readability of the script and the logic layout. To a degree, it also matches the way in which we think and speak; if is a semantic in our spoken language in the same way it is within the bash script.

Even though it will take up more than a single line in the script, with an if statement we can achieve more and make the script more legible. That being said, let's look at creating if conditions. The following is an example of a script using an if statement:

#!/bin/bash 
# Welcome script to display a message to users on login 
# Author: @theurbanpenguin...