Intro to irb
Last updated
Last updated
Describe IRB and why it's useful when programming.
Distinguish IRB from your terminal and other files.
Access and exit IRB via your terminal.
Execute commands in IRB.
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IRB stands for "Interactive Ruby." It's a Ruby shell or REPL. REPL stands for read–eval–print loop. It is a simple, interactive computer programming environment that takes user inputs (such as, in our case, snippets of Ruby code), evaluates them, and returns the result to the user. IRB is run by your computer's terminal.
Reminder: The term 'terminal' refers to the program we use to communicate with our computer via text input. We can type commands one by one into the terminal and it will return responses, similar to the way people used computers before graphical user interfaces.
You can think of it as your Ruby playground or execution environment. You can open it up, insert code and execute it to see that code's return value.
IRB is not a file where you save your work. Any coding you do in the IRB console in your terminal will not get saved anywhere. It only exists temporarily. IRB is for testing, playing, manipulating your code so that you understand it better and solve problems with it.
IRB allows you to execute ruby in the terminal and you're going to get comfortable using it to test and better understand your Ruby code. To access IRB, just type irb in the terminal.
IRB allows you to do anything you can do in a Ruby file. For instance, you can do math, get the time by typing Time.now, or print text to the screen.
Open up your terminal.
In the terminal, type irb and hit return (if you're using Repl.it, you can skip this as the terminal is already set to read Ruby).
Now that you've started IRB, type the commands below to see how it works! Type each of the following lines into the IRB shell and press enter.
Time.now
255 / 5
9 ** 2
puts "hello world"
To leave IRB, type the exit command - this will get you back to your command line.
If Sandbox is enabled, on this lesson's Learn page, you should see a 'Sandbox' button that will open Learn's in-browser IDE. The terminal is the at the bottom of the IDE ()
If you do not have Sandbox, or are not sure how to access the terminal on your computer, you can also go to and create a Ruby based Repl to follow along. Repl.it, just like Sandbox, provides a simulated terminal in the browser that is ready to receive Ruby commands.
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