Introduction to the terminal

Laura edited this page Oct 13, 2015 · 1 revision
Clone this wiki locally

An introduction to the command line / command prompt / terminal

Today we'll teach you some tips and tricks on how to use the terminal (or: command prompt) to make it appear to non-developer bystanders like you're in the matrix. The terminal is more than a place where you enter commands to your computer. You can count how often a word appears in a single file, pull a random Chuck Norris quote using the Chuck Norris API, post a tweet from there or convert a large number of pictures to thumbnails. Just to name a few things. Plus: you don't need to install anything, as every computer has such a terminal thing. Let's get started:

Open your terminal
and... open a texteditor (like Sublime)

Interactive Ruby

Type irb and hit enter and you'll be able to write Ruby code, right in your editor. Run exit to exit interactive Ruby mode again.

We can do some basic stuff, like some math. Try it! Type 2 + 6 and you'll see! Now that was pretty easy, but irb can handle more complex stuff too! Just try:

4 * 10
40 / 4

a = 2
b = 3
a + b

Cool, huh?

Controlling EVERTHING from the terminal

The first thing you have to know about the terminal is: you can't (really) break anything, so even though that giant screen can seem terrifying, you'll get to know it (and enjoy working in it!) super fast! Don't be scared! We have both noticed that using the terminal for EVERYTHING - yes, also when we're just creating a folder to put all are cut cat pictures in - makes you feel really confident with the command line. Give it a try!

mkdir i-am-a-developer to make directory
cd i-am-a-developer
to change into that directory
cd .. to move one directory up
mkdir i-am-a-developer/img to create a folder in a folder
rm i-am-a-developer to delete a folder or directory
ls to list everything in the current directory

Another nifty trick: use the arrows on your keyboard to navigate through previous commands. This will save you a looooot of typing!


We borrowed this part of the tutorial from TryRuby, if you want to improve your 'terminal fluency' - make sure to check out that course!

Type your first name in quotes like this: "Laura"
Congratulations, you've successfully formed a string from the letters of your name. A string is a set of characters the computer can process.

To reverse your name, type: "Laura".reverse (Don't forget the dot!)
You have used the reverse method on your name!

Now, let's make the computer count how many letters are in your name: "Laura".length
Let's multiply your name by 5. "Laura" * 5

You've used English-language methods like reverse and symbolic methods like * (the multiplication method.) Methods are actions!


We can also use IRB again, to greet some planets (because: why not?!).

planet = "mars"
puts planet

and the terminal will 'print' mars.

puts "hello" + planet

and the terminal will 'print' hellomars.

puts "hello " + planet

Notice the extra space (pun intended) after hello? The terminal will 'print' hello mars.

puts "hello " + planet.upcase + "!"

and the terminal will 'print' hello MARS!.

Next we'll create some arrays! Arr-WHAT? Arrays are 'ordered, integer-indexed collections of any object'. Array indexing starts at 0, instead of at 1. A new array can be created by using [].

planets = ["mars", "pluto", "jupiter"]

a puts planets will now return the planets in your array, one by one. What do you think planets.pop(1) does?

... Exactly! It 'pops' one planet out of our array. puts planets will now return only 2 of the 3 planets we originally put in there.

Adding a new planet to our array is equally simple:



Back To The Future

The awesome thing about Ruby is that it knows a LOT of stuff. Let's try to quiz it!

Quite smart, right? It's today's date, indeed! Now try and guess what the following will do.

That's right, the day of the week! But okay, we knew that too. We could try something a little complicated... Like going back in time! Pick any date you want, and type it into your terminal like this (first the year, then the month, and finally the day):

t =, 10, 26)

What we just did was save your special date to a variable called t. Now you can, for example, check whether that day was a monday.


Awesome, right?
If you want to ask your terminal to return the value of your t variable, you can always just type


and press Enter. However, that formatting doesn't look too nice.. Let's strftime the heck out of it! It goes like this:

t.strftime("%A %B %-d %Y")

As you can see in your terminal, %A will give you the day of the week, %B the month, %-d the day of the month, and of course %Y gives you the year. Jippie!

Now we can take our Delorean and travel back in time :)

puts "Delorean successfully travelling to " + t.strftime("%A %B %-d %Y") + " at 88 mph"

We did forget to accelerate though, so here's how you can do that:

(0..88).each do |i|
   puts "Delorean accelerating at #{i} km/h"

Enjoy travelling back and forth in time!