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.

Note

IRB is a default gem of Ruby so you shouldn't need to install it separately.

But if you're using Ruby 2.6 or later and want to upgrade/install a specific version of IRB, please follow these steps.

To install it with bundler, add this line to your application's Gemfile:

gem 'irb'

And then execute:

$ bundle

Or install it directly with:

$ gem install irb

You can start a fresh IRB session by typing irb in your terminal.

In the session, you can evaluate Ruby expressions or even prototype a small Ruby script. An input is executed when it is syntactically complete.

$ irb irb(main):001:0> 1 + 2 => 3 irb(main):002:1* class Foo irb(main):003:2* def foo irb(main):004:2* puts 1 irb(main):005:1* end irb(main):006:0> end => :foo irb(main):007:0> Foo.new.foo 1 => nil

If you use Ruby 2.5 or later versions, you can also use binding.irb in your program as breakpoints.

Once a binding.irb is evaluated, a new IRB session will be started with the surrounding context:

$ ruby test.rb From: test.rb @ line 2 : 1: def greet(word) => 2: binding.irb 3: puts "Hello #{word}" 4: end 5: 6: greet("World") irb(main):001:0> word => "World" irb(main):002:0> exit Hello World

The following commands are available on IRB. You can get the same output from the show_cmds command.

IRB cwws Show the current workspace. chws Change the current workspace to an object. workspaces Show workspaces. pushws Push an object to the workspace stack. popws Pop a workspace from the workspace stack. irb_load Load a Ruby file. irb_require Require a Ruby file. source Loads a given file in the current session. irb Start a child IRB. jobs List of current sessions. fg Switches to the session of the given number. kill Kills the session with the given number. irb_info Show information about IRB. show_cmds List all available commands and their description. Debugging debug Start the debugger of debug.gem. break Start the debugger of debug.gem and run its `break` command. catch Start the debugger of debug.gem and run its `catch` command. next Start the debugger of debug.gem and run its `next` command. delete Start the debugger of debug.gem and run its `delete` command. step Start the debugger of debug.gem and run its `step` command. continue Start the debugger of debug.gem and run its `continue` command. finish Start the debugger of debug.gem and run its `finish` command. backtrace Start the debugger of debug.gem and run its `backtrace` command. info Start the debugger of debug.gem and run its `info` command. Misc edit Open a file with the editor command defined with `ENV["EDITOR"]`. measure `measure` enables the mode to measure processing time. `measure :off` disables it. Context show_doc Enter the mode to look up RI documents. ls Show methods, constants, and variables. `-g [query]` or `-G [query]` allows you to filter out the output. show_source Show the source code of a given method or constant. whereami Show the source code around binding.irb again. 

• NO_COLOR: Assigning a value to it disables IRB's colorization.
• IRB_USE_AUTOCOMPLETE: Setting it to false disables IRB's autocompletion.
• EDITOR: Its value would be used to open files by the edit command.
• IRBRC: The file specified would be evaluated as IRB's rc-file.

https://docs.ruby-lang.org/en/master/IRB.html

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.

rake release gh release create vX.Y.Z --generate-notes 

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