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 explained regular expressions, and two common tools that use them under Linux: grep and sed.

We began by explaining that regular expressions are search patterns, used in combination with text to find matches. These search patterns allow us to search very flexibly in text where its contents are not necessarily known at runtime.

Search patterns allow us, for example, to look only for words and not numbers, for words at the beginnings or endings of lines, or for empty lines. Search patterns include wildcards, which can represent one or more of a certain character or character class.

We introduced the grep command to show how we can use the basic functionality of regular expressions in Bash.

The second part of this chapter dealt with globbing. Globbing is used as a wildcard mechanism for file names and paths. It has similarities with regular expressions, but also some key differences. Globbing can be used with most commands that deal with files (and, since most things under...