How to run IRB (Interactive Ruby)

What is irb?

irb stands for interactive ruby.
It is a tool for easily entering and executing Ruby expressions from standard input.

• by Official

What you can do with irb

By using the irb command from the terminal, you can execute Ruby code line by line on your terminal.
It is a very powerful tool when you want to try out Ruby quickly.

Since you don't need to create a file every time, it is extremely convenient for running small Ruby commands.

Installing irb

You can easily install it using gem.

$ gem install irb
Fetching irb-1.2.7.gem
Fetching io-console-0.5.6.gem
Fetching reline-0.1.8.gem
Building native extensions. This could take a while...
Successfully installed io-console-0.5.6
Successfully installed reline-0.1.8
Successfully installed irb-1.2.7
Parsing documentation for io-console-0.5.6
Installing ri documentation for io-console-0.5.6
Parsing documentation for reline-0.1.8
Installing ri documentation for reline-0.1.8
Parsing documentation for irb-1.2.7
Installing ri documentation for irb-1.2.7
Done installing documentation for io-console, reline, irb after 2 seconds
3 gems installed

Trying out irb

After installation, just type irb.

$ irb
irb(main):001:0> 

For example, let's use the puts command to display "Hello, world".

irb(main):001:0> puts "Hello, world!"
Hello, world!
=> nil
irb(main):002:0> 

It's simple. It is much easier to try out than creating a Ruby file and running it with the ruby command.

Exiting irb

Type exit and press Enter to return to the regular terminal.

irb(main):001:0> exit
$