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)

Regular expression engines

To start with, what are regular expressions?

Regular expressions are strings that the regex engine interprets to match a specific text. It's like an advanced way of searching.

Assume that you want to search a file for lines starting with any small letters, or you want to search for lines that contain a number, or maybe search for lines starting with specific text. The normal search can't be generic: the only way to do that is to use regular expressions.

And what is the regex engine?

The regex engine is the piece of software that understands these strings and translates them to find the matched text.

There are many regex engines out there; for example, the engines that are shipped with programming languages such as Java, Perl, and Python. Also, the engines that Linux tools use are sed and AWK, and the important thing for us now is to learn the...