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

Input/output redirection


In this chapter, we will discuss redirection in Linux in detail.

Simply put, redirection is pretty much exactly as the word implies: the redirecting of something to something else. For example, we've already seen that we can use the output of one command as the input for the next command, using pipes. Pipes are implemented in Linux using the | sign.

However, that might raise the question: how does Linux deal with input and output in the first place? We'll begin our journey into redirection with some theory on file descriptors, which are what make all redirection possible!

File descriptors

You might be tired of hearing it, but it is still no less true: in Linux, everything is a file. We've seen that a file is a file, a directory is a file, even hard disks are files; but now, we'll take this one step further: your keyboard, which you use for input, is also a file!

Complementary to that, your Terminal, which commands use as output, is, guess what: a file.

You can find these...