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Table of Contents

Preface

Introduction to Linux and shells

man

ls

cd

pwd

mkdir

rmdir

mv

cp

touch

find

ln

gzip

gunzip

tar

alias

cat

less

tail

wc

grep

sort

uniq

diff

echo

history

export

crontab

uname

env

printenv

Conclusion

Preface

The Linux Commands Handbook follows the 80/20 rule: learn in 20% of the time the 80% of a topic.

I find this approach gives a well-rounded overview.

This book does not try to cover everything under the sun related to Linux and its commands. It focuses on the small core commands that you will use the 80% or 90% of the time, trying to simplify the usage of the more complex ones.

All those commands work on Linux, macOS, WSL, and anywhere you have a UNIX environment.

I hope the contents of this book will help you achieve what you want: get comfortable with Linux.

This book is written by Flavio. I publish programming tutorials every day on my website flaviocopes.com.

You can reach me on Twitter @flaviocopes.

Enjoy!

A "distro" is made by a company or organization and packages the Linux core with additional programs and tooling.

For example you have Debian, Red Hat, and Ubuntu, probably the most popular.

Many, many more exist. You can create your own distribution, too. But most likely you'll use a popular one, one that has lots of users and a community of people around it, so you can do what you need to do without losing too much time reinventing the wheel and figuring out answers to common problems.

Some desktop computers and laptops ship with Linux preinstalled. Or you can install it on your Windows-based computer, or on a Mac.

But you don't need to disrupt your existing computer just to get an idea of how Linux works.

I don't have a Linux computer.

If you use a Mac you need to know that under the hood macOS is a UNIX Operating System, and it shares a lot of the same ideas and software that a GNU/Linux system uses, because GNU/Linux is a free alternative to UNIX.

UNIX is an umbrella term that groups many operating systems used in big corporations and institutions, starting from the 70's

The macOS terminal gives you access to the same exact commands I'll describe in the rest of this handbook.

Microsoft has an official Windows Subsystem for Linux which you can (and should!) install on Windows. This will give you the ability to run Linux in a very easy way on your PC.

But the vast majority of the time you will run a Linux computer in the cloud via a VPS (Virtual Private Server) like DigitalOcean.

A shell is a command interpreter that exposes to the user an interface to work with the underlying operating system.

It allows you to execute operations using text and commands, and it provides users advanced features like being able to create scripts.

This is important: shells let you perform things in a more optimized way than a GUI (Graphical User Interface) could ever possibly let you do. Command line tools can offer many different configuration options without being too complex to use.

There are many different kind of shells. This post focuses on Unix shells, the ones that you will find commonly on Linux and macOS computers.

Many different kind of shells were created for those systems over time, and a few of them dominate the space: Bash, Csh, Zsh, Fish and many more!

All shells originate from the Bourne Shell, called sh. "Bourne" because its creator was Steve Bourne.

Bash means Bourne-again shell. sh was proprietary and not open source, and Bash was created in 1989 to create a free alternative for the GNU project and the Free Software Foundation. Since projects had to pay to use the Bourne shell, Bash became very popular.

If you use a Mac, try opening your Mac terminal. That by default is running ZSH. (or, pre-Catalina, Bash)

You can set up your system to run any kind of shell, for example I use the Fish shell.

Each single shell has its own unique features and advanced usage, but they all share a common functionality: they can let you execute programs, and they can be programmed.

In the rest of this handbook we'll see in detail the most common commands you will use.

command, with some handy examples of common usage scenarios:

This is not a substitute for man , but a handy tool to avoid losing yourself in the huge amount of information present in a man page. Then you can use the man page to explore all the different options and parameters you can use on a command.

ls

Inside a folder you can list all the files that the folder contains using the ls command:

ls

If you add a folder name or path, it will print that folder contents:

ls /bin

ls accepts a lot of options. One of my favorite options combinations is - al. Try it:

ls -al /bin

cd

Once you have a folder, you can move into it using the cd command. cd means c hange d irectory. You invoke it specifying a folder to move into. You can specify a folder name, or an entire path.

Example:

mkdir fruits cd fruits

Now you are into the fruits folder.

You can use the .. special path to indicate the parent folder:

cd .. #back to the home folder

The # character indicates the start of the comment, which lasts for the entire line after it's found.

You can use it to form a path:

mkdir fruits mkdir cars cd fruits cd ../cars

There is another special path indicator which is. , and indicates the current folder.

You can also use absolute paths, which start from the root folder / :

cd /etc

This command works on Linux, macOS, WSL, and anywhere you have a UNIX environment

mkdir

You create folders using the mkdir command:

mkdir fruits

You can create multiple folders with one command:

mkdir dogs cars

You can also create multiple nested folders by adding the -p option:

mkdir -p fruits/apples

Options in UNIX commands commonly take this form. You add them right after the command name, and they change how the command behaves. You can often combine multiple options, too.

You can find which options a command supports by typing man . Try now with man mkdir for example (press the q key to esc the man page). Man pages are the amazing built-in help for UNIX.

rmdir

Just as you can create a folder using mkdir , you can delete a folder using rmdir :

mkdir fruits rmdir fruits

You can also delete multiple folders at once:

mkdir fruits cars rmdir fruits cars

The folder you delete must be empty.

To delete folders with files in them, we'll use the more generic rm command which deletes files and folders, using the -rf options:

rm -rf fruits cars

Be careful as this command does not ask for confirmation and it will immediately remove anything you ask it to remove.

There is no bin when removing files from the command line, and recovering lost files can be hard.

cp

You can copy a file using the cp command:

touch test cp apple another_apple

To copy folders you need to add the -r option to recursively copy the whole folder contents:

mkdir fruits cp -r fruits cars

touch

You can create an empty file using the touch command:

touch apple

If the file already exists, it opens the file in write mode, and the timestamp of the file is updated.