Learning Modern Linux

Chapter 3. Shells and Scripting

In this chapter, we’ll focus on interacting with Linux on the terminal, that is, via the shell that exposes a command-line interface (CLI). It is vitally important to be able to use the shell effectively to accomplish everyday tasks, and to that end we focus on usability here.

First, we review some terminology and provide a gentle and concise introduction to shell basics. Then we have a look at modern, human-friendly shells, such as the Fish shell. We’ll also look at configuration and common tasks in the shell. Then, we move on to the topic of how to effectively work on the CLI using a terminal multiplexer, enabling you to work with multiple sessions, local or remote. In the last part of this chapter, we switch gears and focus on automating tasks in the shell using scripts, including best practices for writing scripts in a safe, secure, and portable manner and also how to lint and test scripts.

There are two major ways to interact with Linux, from a CLI perspective. The first way is manually—that is, a human user sits in front of the terminal, interactively typing commands and consuming the output. This ad-hoc interaction works for most of the things you want to do in the shell on a day-to-day basis, including the following:

• Listing directories, finding files, or looking for content in files

• Copying files between directories or to remote machines

• Reading emails or the news or sending a Tweet from the terminal

Further, we’ll learn how to ...