Bash Scripting Language

The Default Interactive Linux Shell

/bin/bash is premature optimization. @beginbot

Bourne Again Shell is default interactive user shell of the Linux operating system. It is also a powerful scripting language known for creating useful scripts complex single-line commands quickly. As such it has a rather unusual syntax when compared to other languages. Bash usage and programming are a primary focus of the Linux Beginner Boost.

Bash Shell Survival

Whether you are just starting out as a new technologist or have been one for a while but not really learned the terminal command line shell then you might find yourself stuck or not knowing what to do. Here’s a minimal survival guide to help you out or get you started. Remember as you master these that there is a lot more to come. Don’t worry about understanding every, single option with every command at the moment or even why they do what they do. That will come in time.

Before you get started make sure you understand all the keyboard symbols and just know that you can usually combine two options that use a dash like ls -al.

If you happen to know (or have had someone else tell you about) the ls aliases like ll just don’t use them for now. It is far more important for you to learn the actual commands, not the alias shortcuts. Later after you have really mastered the actual command and options consider adding your own aliases.

Cozy Shell Commands

First the cozy commands, those that make you feel at home and like you know where you are, how to get around, what stuff is, and what’s inside.

Command Description
ls List visible files and directories in the current directory.
ls -a List all files and directories in the current directory.
ls -l List the details of files and directories including permissions.
pwd Print the working directory (where you are).
clear Clear the screen. Do not use Control+L!
cd Change into the home directory from anywhere.
cd .. Change parent of current directory. The two dots .. mean parent.
cd - Change into the previous directory, which is nice for changing back and forth a lot.
cat <file> Shows the content of the file.
less <file> Shows the content of a long file that you can page through with Space. Remember q to quit.
type <this> Check if this command exists, what type of command it is (alias, function, binary executable), and where it lives.

Existential Shell Commands

Now for the existential commands that create, change, and delete stuff. You don’t need to fear these commands, just be more careful when using them. There is no undo on the Linux command line (until you get Git setup).

Command Description
file <file> Show what kind of file it is.
mkdir <dir> Make a new directory.
touch <file> Create a new empty file. (Or update the time stamp of the file.)
mv <old> <new> Rename a file or directory.
rm <file> Remove a file.
rmdir <dir> Remove an empty directory. (Use rm first for the files until it is empty.)
chmod u+x <file> Change a plain text file into an executable script command.
./<script> Run a newly made command script in the current directory.

There is a reason dangerous advanced commands like rm -rf <dir> and brain-dead things like Control-L to clear your screen are not included in this survival shell section. It is designed for beginners who might seriously mess themselves up knowing these options exist at this time. Eventually everyone should learn the more advanced options, just not right now.

By the way, if you do not understand why Control-L is so bad to burn into your muscle memory you simply have not yet learned basic command line Linux usage at all. Keep reading and researching. You’ll get there.

Don’t forget to know all the extra key combinations and how to get yourself unstuck.

Omissions

There are several valuable and important elements of Bash that the book leaves out. Make sure you understand them.

See Also