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

Final remarks


Regular expressions are hard. What makes this even harder on Linux is that regular expressions have been implemented by different programs (which have different maintainers, with different opinions) slightly differently.

To make matters worse, some features of regular expressions have been hidden as extended regular expressions by some programs, whereas they are considered the default by other programs. In past years, the maintainers of these programs seemed to have moved towards a more global POSIX standard for regular regular expressions and extended regular expressions, but still to this day, there are some discrepancies.

We have some very simple advice for dealing with this: just try it out. You might not remember what the asterisk represents in globbing, as opposed to regular expressions, or why the question mark does something different. Perhaps you'll forget to 'activate' extended syntax with -E, and your extended search pattern will return weird errors.

You will definitely...