IRB

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.

Installation

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

Usage

The irb Executable

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

The binding.irb Breakpoint

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

Commands

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.

Configuration

Environment Variables

• 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.

Documentation

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

Development

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.

Contributing

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

Releasing

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

License

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