irb

Goals

Understand the difference between irb and the command line
Understand how and when to use irb
Execute some simple ruby statements

Step 1

Type this in the terminal:
irb
irb is the interactive ruby interpreter.

In irb, you can experiment with short pieces of code to figure out what they do.

Step 2

Type this in irb:
5 + 9
109 / 17
2 ** 8
5 > 6
What happened after each line? What do you think these statements do?

Step 3

Lets take a closer look at the output of irb:
Type this in irb:
1 + 2
Expected result:
1.9.3p125 :015 > 1 + 2
 => 3 
1.9.3p125 :016 > 
Here, => 3 is the return value of the statement 1 + 2. Every statement in ruby has a return value: irb shows you that value after you type a complete statement and press enter.

Step 4

Type this in irb:
exit
exit is the guaranteed way to get out of irb. Depending on your operating system, Control-C or Control-D on an empty line may also work.

Practice going in and out of irb a couple of times. How can you tell when you're in or out of irb?

Explanation

irb isn't a place to write code: it's a place to experiment and find out how certain language features work. When you write a full-fledged program, you'll save it into a text file on your computer.

Next Step:

Go on to Variables

Back to Command Line