unix command line basics

This is the document I wish I had when I started using Unix command line interfaces (CLI). There are already many beginner’s guides to using a unix CLI online, but I feel most of them skip some important commands. This article assumes you already know some of the most essential commands, and how to pass arguments to commands - if not, read this article first. If your using a Windows machine and are new to using CLIs, note that the CLIs that come with Windows operating systems are Command Prompt and Powershell which are not Unix CLIs, but you can install a Unix CLI on your Windows computer if you desire.

man

Some beginner’s guides don’t teach this command, but I think it’s most important because it shows manuals (ie instructions) for how to use other commands. For example, to learn how to use the command ls or to see what arguments you can pass to that command, enter man ls into your CLI. After displaying the instructions, press q to quit or h to show the help page which, among other things, will tell you how to navigate the manuals using your keyboard. Alternatively if you prefer a webpage, google “man ” and a link to a webpage with the command’s manual will almsot certainly be the first result.

pwd

Stands for Present Working Directory, ie current directory. This just prints the current directory you’re working from currently.

Prints the present working directory (ie the directory you’re currently inside) to the screen.

less

You may know the command cat, but what if you want to navigate/read through a file and not just have all it’s text dumped to your screen? Use the command less. You can use the same keys to navigate files opened using less as the commands that you use to navigate man pages.

nano

Sometimes you may need to edit a file with text in it. One of the easiest ways to do this from the command line is to use the nano text file editor. Simply type nano <path to your file> to open up a text editor in your CLI environment. Again, if you need help learning how to use the nano editor, you can use man nano (and google is always an option). There are numerous other CLI text editors, with vim probably being the most used, but since it requires a learning curve, I’d reccomend nano to beginners.

mkdir

Create a directory (eg a folder). Just type mkdir <directory name>.

sudo

If you’re new to using CLIs, it’s good to be aware of this command because it may not be obvious when you need it. If you ever try to give a command that you don’t have permissions for, you CLI may compalin that you don’t have permission to do it. For example:

$ apt-get update
Reading package lists... Done
E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)
E: Unable to lock directory /var/lib/apt/lists/
W: Problem unlinking the file /var/cache/apt/pkgcache.bin - RemoveCaches (13: Permission denied)
W: Problem unlinking the file /var/cache/apt/srcpkgcache.bin - RemoveCaches (13: Permission denied)

Here I’m trying to update my package manager, but I see that the CLI says I don’t have permission. I can fix this by simply appending sudo to the begginning of my command and doing sudo apt-get update. My computer will then prompt me for my password before executing the command. Note that when you enter your password into the CLI, it will show no ticks or dots to register that it’s receiving your keyboard input - this can throw off beginners.

This is also a good time to mention various expansions that are available in unix CLIs:

• !!: Expands to the last command you executed. For example, if you entered apt-get update as in the previous example, but now you want to prepend sudo to the command, you could enter sudo !! which the CLI will interpret as sudo apt-get update.
• *: This is the “wildcard” operator. See some helpful examples of using it here.

Any other commands you wish you knew when you started out using CLIs? Let me know using the form at the bottom of this page.