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Latest commit

* Allow using IRB_USE_AUTOCOMPLETE=false to disable autocompletion

Currently, the only 2 ways to disable autocompletion are:

1. Create `.irbrc` and set `IRB.conf[:USE_AUTOCOMPLETE] = false`
2. Add the `--noautocomplete` flag when using the `irb` executable

Both of them are less convenient than setting a env var and are
lesser known to devs.

And given the number of problems the autocompletion has (see #445), I
think we should allow disabling it with a simple `IRB_USE_AUTOCOMPLETE=false`.

* Mention some env var configs in the README

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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.


The following commands are available on IRB.

  • cwws
    • Show the current workspace.
  • cb, cws, chws
    • Change the current workspace to an object.
  • bindings, workspaces
    • Show workspaces.
  • edit
    • Open a file with the editor command defined with ENV["EDITOR"]
      • edit - opens the file the current context belongs to (if applicable)
      • edit foo.rb - opens foo.rb
      • edit Foo - opens the location of Foo
      • edit - opens the location of
      • edit Foo#bar - opens the location of Foo#bar
  • pushb, pushws
    • Push an object to the workspace stack.
  • popb, popws
    • Pop a workspace from the workspace stack.
  • load
    • Load a Ruby file.
  • 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.
  • help
    • Enter the mode to look up RI documents.
  • irb_info
    • Show information about IRB.
  • ls
    • Show methods, constants, and variables. -g [query] or -G [query] allows you to filter out the output.
  • measure
    • measure enables the mode to measure processing time. measure :off disables it.
  • $, show_source
    • Show the source code of a given method or constant.
  • @, whereami
    • Show the source code around binding.irb again.
  • debug
    • Start the debugger of debug.gem.
  • break, delete, next, step, continue, finish, backtrace, info, catch
    • Start the debugger of debug.gem and run the command on it.


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.



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


Bug reports and pull requests are welcome on GitHub at


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.