When you're in the command line, you'll see a prompt that looks like this:
$
You may also see your username to the left of the $. Let's try our first command. Type the following and press enter:
$ whoami
The whoami command should print out your username. Congrats, you've executed your first command! This is a basic pattern of use in the command line: type a command and receive output.
OK, we're going to try another command. But first, let's make sure we understand some things about how your computer's filesystem works.
Your computer's files are organized in what's known as a hierarchical filesystem. That means there's a top level or "root" folder on your system. That folder has other folders in it, and those folders have folders in them, and so on. You can draw these relationships in a tree:
Users
|
-- patrick
|
-- Photos
-- Documents
The root or highest-level folder on OSX is just called /. We won't need to go in there, though, since that's mostly just files for the operating system. On Windows, the root directory is usually called C:.
OK, let's try a command that tells us where we are in the filesystem:
$ pwd
You should get output like /Users/patrick. That means you're in the patrick directory in the Users folder inside the / or root directory. On Windows, your output would instead be C:/Users/patrick. The folder you're in is called the working directory, and pwd stands for "print working directory."
OK, we know where we are. But what if we want to know what files and folders are in the patrick directory, a.k.a. the working directory? Try entering:
ls
You should see a number of folders, probably including Documents, Desktop, and so on. You may also see some files. These are the contents of the current working directory.
I wonder what's in the Desktop folder? Let's try moving to it with the following command:
$ cd Desktop
(Make sure the "D" in "Desktop" is capitalized. ) If the command was successful, you won't see any output. This is normal—often, the command line will succeed silently.
So how do we know it worked? That's right, let's use our pwd command again. We should get:
$ pwd
/Users/patrick/Desktop
Now try ls again to see what's on your desktop. These three commands—pwd, ls, and cd—are the most commonly used in the terminal. Between them, you can orient yourself and move around. Before we move on, let's take a minute to move around in the command line.
Use the three commands you've just learned—pwd, ls and cd—eight (8) times each. Go poking around your Photos folder, or see what's so special about that scary root / directory. When you're done, come back to the home folder with
cd ~
(That's a tilde, on the top left of your keyboard.) One more command you might find useful is
cd ..
which will move you one directory up in the filesystem. That's a cd with two periods after it.
