IRB stands for "interactive Ruby" and is a tool to interactively execute Ruby expressions read from the standard input.

The irb command from your shell will start the interpreter.

Add this line to your application's Gemfile:

gem 'irb'

And then execute:

$ bundle

Or install it yourself as:

$ gem install irb

Use of irb is easy if you know Ruby.

When executing irb, prompts are displayed as follows. Then, enter the Ruby expression. An input is executed when it is syntactically complete.

$ irb
irb(main):001:0> 1+2
#=> 3
irb(main):002:0> class Foo
irb(main):003:1>  def foo
irb(main):004:2>    print 1
irb(main):005:2>  end
irb(main):006:1> end
#=> nil

The Readline extension module can be used with irb. Use of Readline is default if it's installed.

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/ruby/irb.

The gem is available as open source under the terms of the 2-Clause BSD License.