Part I - Introduction

About the course

The goal of this course is to improve familiarity with Unix-like operating systems. Before we begin, though, we should ask: why do Unix-like operating systems matter?

Why "Unix-like"?

"macOS Sierra" is copyright Apple, Inc. Used with permission.

Chances are, you're running a Unix-like system right now. The popular Apple macOS is Unix-like. (Actually, since version 10.5--code named "Leopard"--OSX hasn't just been "Unix-like," it's officially fully Unix. This distinction probably doesn't mean much right now; Chapter 4 - A Brief History of Unix has more details.)

If you're running Mac OSX, the concepts we cover here will be directly applicable to your day-to-day computing.

"Discos de Ubuntu 8.10 (Intrepid Ibex)" by Gonzalo Díaz is Licensed under CC BY 2.0

GNU/Linux is another world-famous Unix-like operating system. Popular variants include Debian, Redhat, and Ubuntu (pictured).

While GNU/Linux is not as common on the desktop as Microsoft Windows or Apple macOS, it is widely deployed in server technology. Professionals working in the field of software development (especially for web-based technologies) will likely come across this operating system in the course of deploying their work.

User-unfriendly

"Schlock. Manchester, England" by Nathan Makan is licenced under CC BY-NC-ND 2.0

Many aspects of using Unix and its derivatives are non-obvious, and some are downright confusing. We hope to help students understand the fundamentals so that they can begin to feel more comfortable:

• working from a text-based command prompt
• using essential utility applications
• composing custom scripts to automate work and solve problems
• perform basic system administration tasks

Whenever possible, we try to explain the rationale behind the system design so that students will not have to rely on rote memorization to build confidence.

Reading the Code Examples

pc$ code blocks like these represent a terminal
they are intended to demonstrate various commands
and their effects
pc$ 

Lines that begin with pc$ describe commands that are intended to be entered into your system's terminal. The pc$ is sometimes referred to as the "prompt", and it is intended to designate input lines. The "command" is all the text that follows the prompt; when typing the command on your system, you should not include the prompt.

Lines that do not begin with the prompt are "output" lines. This is text produced in response to the command.

Note that terminal examples from other guides use the lone dollar sign character ($) or even the "hash" character (#) as the prompt. Whatever it looks like, the prompt's purpose is the same: to designate the command that should be typed.

Complete operating systems can be run as standalone processes. These are known as "virtual machines," and you can use them to run any operating system within any other operating system.

A GNU/Linux virtual machine (specifically, of the Ubuntu distribution) has been prepared for this course. This means that regardless of the operating system you are using today, you will experiment and learn inside the exact operating system that the course requires.

pc$ this command should be run on your system
this is output from your system

vm$ this command should be run in the virtual machine
this is output from the virtual machine

A small number of commands in this course are intended to be run on your system, but most of them should be executed within the virtual machine.

The pc$ prompt denotes commands that are intended to be run on your system. We'll use the vm$ prompt to denote the commands that are intended for the virtual machine.

A note on shells

The terms of Unix-like systems, the word "shell" refers to any program that provides a text interface to the system. There are many shell applications available (this is just a partial list), and they differ substantially.

Because all interaction is mediated by the shell (Chapter 6 - Command Invocation has a more complete discussion of this), the distinction between features provided by the system and features provided by the shell can be subtle.

This course focuses on system-provided functionality because that is relevant regardless of one's chosen shell. Whenever course content describes shell-provided functionality, this distinction is explicitly described. In these cases, content is limited to the feature set that is shared by the more common shells: bash, sh, and zsh.

Students who are interested in using shell-specific features have advanced beyond the abilities of this course's target audience.

About the exercises

"Vagrant Logo" by Fco.plj is licensed under CC BY-SA 3.0

In order to provide a consistent experience for all students across all platforms, interactive exercises for this course are authored to be completed within a "virtual machine." Thanks to the free and open source software VirtualBox, Vagrant, and Ubuntu, students can complete the exercises in a purpose-built Unix-like environment using their personal computer and at no charge. Chapter 2 - Setup includes instructions for installing these tools.

The default user account in the exercise environment is named "vagrant", and it is configured to use the Bash shell. Administrative access requires a password, and that password is "vagrant".

About the course

Command the Command Line was created in 2016 at Bocoup. It is currently maintained by Mike Pennisi.