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 almost everything there is to know about redirection on Linux. We began with a general description of what redirection is, and how file descriptors are used to facilitate redirections. We learned that file descriptors 0, 1, and 2 are used for stdin, stdout, and stderr, respectively.

We then got acquainted with the syntax for redirections. This included >, 2>, &>, and <, and their appending syntaxes, >>, 2>>, &>>, and <<.

We discussed a few special Linux devices, /dev/null, /dev/zero, and /dev/urandom. We showed examples of how we could use these devices to remove output, generate null bytes, and generate random data. In the advanced redirecting section, we showed that we could bind stdout to stderr and vice versa.

Furthermore, we learned about command substitution and process substitution, which allows us to use the result of a command in an argument to another command, or as a file.

Next up were pipes. Pipes are simple...