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You're probably used to files and folders as they show up on your desktop. You can drag them around, put them in other folders, and so forth. As it turns out, the command line gives you access to the exact same thing.

The simplest command that interacts with your files is pwd. This stands for "print working directory," and if you run it, you'll see your current working directory:

$ pwd
/home/user

This is a very important concept: Every shell always has a working directory and you can always check what it is with pwd. A working directory is itself not too strange a concept: If you open up your files app, you'll see you're looking at some files. You can click on a directory to see the files and folders in that folder, and keep going however long you'd like. It's the same thing here. To see everything that's in your current directory, run ls:

$ ls
Desktop Documents Downloads go Mail Music Pictures Public Templates Videos

Just like in your GUI files app, you can change your working directory. To do so, use the cd command:

$ cd Documents

You'll notice that nothing happened. However, run pwd again and you'll see you're somewhere else:

$ pwd
/home/<your-username>/Documents

As before, you can run ls to see all your documents:

$ ls
essay.txt cstar-guide.html shoelaces.pdf

The so-called parent directory of your working directory is referred to with ... This means that after you cd into Documents, you can get out just as easily:

$ pwd
/home/<your-username>/Documents
$ cd ..
$ pwd
/home/<your-username>
$ cd Documents
$ pwd
/home/<your-username>/Documents

ls is a command you'll be using a lot, so it's worth spending a little bit of time on it. Just like with echo, ls can take arguments. Try using the -l argument for a long listing:

$ ls -l
-rw-r--r--. 1 user group    0 Jan 24 12:13  essay.txt
-rw-r--r--. 1 user group   45 Jan 28 19:00  cstar-guide.html
-rw-r--r--. 1 user group 100M Jul 22  2024  shoelaces.pdf

Reading the output right-to-left, you'll see that we have the filenames just as before. Then, we have the time the files were last modified, preceded by their size. In this example, essay.txt is entirely empty. cstar-guide.html takes up 45 bytes of space, and the M in the 100M taken by shoelaces.pdf stands for megabytes. We'll come back to the rest of the output later, in the section on file permissions.

The echo command can actually be used to create files. Try, for instance, the following:

$ echo "Hello!" > a.txt

This > is called a redirect, and takes the output of the command (which would normally just be "Hello!") and writes it to a file instead.

Now, if you run ls again, you'll see the same output as before, with one addition:

$ ls
a.txt essay.txt cstar-guide.html shoelaces.pdf

Now that you have that file saved to your disk, the cat command will let you see the contents:

$ cat a.txt
Hello!

The greatest sin of the command line environment is that cat has nothing to do with actual cats, and instead is an abbreviation of concatenate. You can pass two or more filenames as arguments to cat, and you'll be able to see them both, one after the other:

$ echo "Goodbye!" > b.txt
$ cat a.txt b.txt
Hello!
Goodbye!

Redirections work on every command, cat included. Try this:

$ cat a.txt b.txt > c.txt

Now, c.txt has the same content as a.txt and b.txt combined, and if you cat it, you'll see what you expect:

$ cat c.txt
Hello!
Goodbye!

By the way, you can't just cat any arbitrary file. Consider, for example, shoelaces.pdf. This thing is 100M, and, being a PDF, it probably has all sorts of information about formatting, page size, and so forth that just isn't expressed as plain text. It's usually inadvisable to cat these to your terminal, unless of course you're redirecting the output to a file.

You probably want to get rid of a.txt, b.txt, and c.txt now. You can do that from the command line as well:

$ rm a.txt b.txt c.txt

Maybe you want to look for any other .txt files just in case you missed some. This can be achieved with a glob:

$ ls *.txt
essay.txt

Now that you know how to create and remove files, it's good to do the same for directories. The mkdir command does the first:

$ mkdir test-directory

And rm does the second:

$ rm -r test-directory

Notice the -r flag. This causes a recursive removal. That is, you're not just removing the directory you specify (here, that's test-directory), but also all the files and folders inside. Be very careful with this command. Unlike the normal files app, there's no trash can to restore from!

Now that you can make and remove files and folders, you've already mastered about half of the command line. Next up are some niceties in line editing.