Hello fellow command line interface (cli) adepts!

Last time we found our terminal programs, and today we’re not afraid to use them. We probably should be, but we’ll leave that discussion for another day.

As mentioned in my last post once we open our terminal program we’re presented with $> or #> or maybe gabe@desktop:~$ or who knows what. Technically, since the prompt is configurable it could say anything. When I was just a wee lad, I had mine set to say:

C:\ What is thy bidding? >

I kid you not.

In case you didn’t leave your terminal program running all night, please go open it now. At this point you should see your prompt, and you should be able to type stuff at your computer. Try it! Most things will cause the computer to reply rudely that it has no idea what you mean. Below are some examples of me typing a command (that thing that follows the $> prompt) followed by the computer’s output. Feel free to type these on your own system as we go (don’t forget to hit return after each one):

First, I try saying hello:

$> hello

To which my system replies:

ksh: hello: not found 

Then I try asking how the computer is doing:

$> how are you doing?

The computer’s reply:

ksh: how: not found

How about asking the computer to please do something:

$> do something please

Computer says:

ksh: syntax error: `do' unexpected

right, very helpful computer. No wonder someone invented the mouse.

The main problem we have is communication. I don’t know what the terminal wants me to say, and the terminal doesn’t know what I want it to do. On top of that there doesn’t seem to be a way to ask it for help, or is there?

$> help

(If you type help, and get a bunch of text but no prompt, you should either press the space bar to scroll the text until the prompt comes back, or press ‘q’ to quit out of the message and return to the prompt.)

On my OpenBSD system I get a very helpful message that actually seems quite useful (I admit I’m kind of shocked). Your system may not be as helpful, so I’m sharing a link to the message I see: http://man.openbsd.org/OpenBSD-current/man1/help.1)

Even if you’re not on an OpenBSD system, I recommend reading that. Go ahead, I’ll wait.

That basically just gave you everything you need to know about the UNIX cli (command line interface). Thankfully, I’m going to pretend it didn’t and carry on as if I didn’t just read that incredibly helpful manual page.

For the rest of this guide I’ll use the following convention. When you see two lines like this:

$> whoami
gabe

The first line is what I type (after the $> prompt), and the second line (or multiple lines) is what the computer replies. So, in the example above, I typed the command whoami, and the computer replied gabe.

So, we’re at our prompt, and we’ve just read about some pretty cool things we can do, lets try one:

$> pwd
/home/gabe

That ‘prints working directory’ - it’s equivalent to looking in your file manager to see what folder you are currently in. That is normally read “slash home slash gabe.” If I were in the Taxes folder under Documents, pwd would return: /home/gabe/Documents/Taxes. The pwd command will always tell you every folder above the one you are currently in. On most UNIX systems the /home (slash home) folder is where all user accounts live. Each user of the system should have a folder below /home. For example if I have 3 users (gabe, joebob, and ariadne) each of us would have a folder inside the home folder:

/home/gabe 
/home/joebob
/home/ariadne

(Note: On a Mac, /home is empty and all user folders exist inside the /Users directory)

There are a plethora of commands available on a UNIX system, and we’ll cover several of them in the next few posts.

New Terms

• whoami - A program that returns the currently logged in user’s account name.

• pwd - A program that returns the current directory along with all of the directories above it.

• /home (slash home) - A directory that contains directories for each user on a system.

• /Users (slash Users) - The Mac equivalent of /home.

• help - A program that (at least on my system) returns a very helpful message informing the user about the system.