So you have decided to try a free software operating system such as GNU/Linux, congratulations. GNU/Linux is not that different from other operating systems on the surface. You point and click using the mouse and call down menus to get programs to work.

However, these icons and windows are just the sweet candy coating on top of a much older system, a system of programs designed to be accessed by the command line.

If you know the correct commands, then you can start any program, check your computer’s status, and see what files you have stored without having to find the listing in your menu

The command line is an interface that allows you to talk directly to your computer using words called commands. If you know the correct commands, then you can start any program, check your computer’s status, and see what files you have stored without having to find the listing in your menu. Also, some functions can only be accessed through the command line, so if you want to truly understand your new system it is worth learning.

First, open a terminal on your computer screen. It will usually list the computer name, or yourname @ yourcomputer and there will be some kind of punctuation mark like a $ or a # followed by a blinking box or line-shaped cursor. That blinking thing is called a prompt because it is prompting you to give it a command. Think of it as a genie coming out of a lamp asking you. “What is your command my master?”

What is your command my master?

If you are at your computer now, you may want to follow along. Open a terminal and then type whoami. (Remember to run all of the words together with no spaces, and press enter.) Here’s what you get:

$ whoami
rosalyn
$

This may seem to be a bit of a philosophical question to be asking your computer, but don’t worry. Your computer has a very concrete world-view.

It should return your login name. The word that you just typed is a command. The computer executed the command and returned a result, your username.

Using commands

Commands are written in a particular way. The command is typed first with no spaces in the name. Then after a space, you can sometimes modify the command by adding what are called options. Options change or limit the way the command is executed. Options are usually preceeded by a dash. A command may also include the name of a file or directory that you want the command to work on. The finished command will look something like this.

command -option file

The best way to understand the command line is to use it. Try typing ls.

Remember that GNU/Linux is case sensitive so you must use lower case. When you press enter, the computer will return to you a list of file names in the directory that you are in. The command ls stands for list.

When I type this command, I get the following response:

$ ls
captions.txt  photo1.png
$

Files are documents, images or programs on your computer. Directories are like boxes that hold the files. You are always considered to be within some directory. Most of the time, commands only act on the files within the directory in which you are located. So, when you list using ls, you get a list of all of the files in the directory that you are in, not all of the files in the computer.

When you use the command line, you are learning to talk “face to face” with your system. You can tell it precisely and concisely what you want it to do. There is something truly freeing about this power

Command names are usually shorthand ways of representing a word, such as ls for list, or mv for move. Sometimes, however, they are oddly abbreviated. Using the command line requires you to learn the names of the commands. The advantage is that by learning the language you can talk directly to the computer without needing a point and click interpreter program explaining what you mean.

When you type ls the names of all of the files in your current directory are written on the terminal screen, and the prompt returns waiting. It is asking, “What next my master?”