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
• Usage
  • The irb Executable
  • The binding.irb Breakpoint
• Commands
• Debugging with IRB
  • More about debug.gem
  • Advantages Over debug.gem's Console
• Type Based Completion
  • How to Enable IRB::TypeCompletor
  • Advantage over Default IRB::RegexpCompletor
  • Difference between Steep's Completion
• Configuration
  • Environment Variables
• Documentation
• Extending IRB
• Development
• Contributing
• Releasing
• License

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

[!Note]

We're working hard to match Pry's variety of powerful features in IRB, and you can track our progress or find contribution ideas in this document.

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> 1 + 2
=> 3
irb(main):002* class Foo
irb(main):003*   def foo
irb(main):004*     puts 1
irb(main):005*   end
irb(main):006> end
=> :foo
irb(main):007> 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 help command.

Help
  help           List all available commands. Use `help <command>` to get information about a specific command.

IRB
  context        Displays current configuration.
  exit           Exit the current irb session.
  exit!          Exit the current process.
  irb_load       Load a Ruby file.
  irb_require    Require a Ruby file.
  source         Loads a given file in the current session.
  irb_info       Show information about IRB.
  history        Shows the input history. `-g [query]` or `-G [query]` allows you to filter the output.
  disable_irb    Disable binding.irb.

Workspace
  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.
  cd             Move into the given object or leave the current context.

Multi-irb (DEPRECATED)
  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.

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 or source location.
  measure        `measure` enables the mode to measure processing time. `measure :off` disables it.

Context
  show_doc       Look up documentation with RI.
  ls             Show methods, constants, and variables.
  show_source    Show the source code of a given method, class/module, or constant.
  whereami       Show the source code around binding.irb again.

Helper methods
  conf           Returns the current IRB context.

Aliases
  $              Alias for `show_source`
  @              Alias for `whereami`

Debugging with IRB

Starting from version 1.8.0, IRB boasts a powerful integration with debug.gem, providing a debugging experience akin to pry-byebug.

After hitting a binding.irb breakpoint, you can activate the debugger with the debug command. Alternatively, if the debug method happens to already be defined in the current scope, you can call irb_debug.

From: test.rb @ line 3 :

    1:
    2: def greet(word)
 => 3:   binding.irb
    4:   puts "Hello #{word}"
    5: end
    6:
    7: greet("World")

irb(main):001> debug
irb:rdbg(main):002>

Once activated, the prompt's header changes from irb to irb:rdbg, enabling you to use any of debug.gem's commands:

irb:rdbg(main):002> info # use info command to see available variables
%self = main
_ = nil
word = "World"
irb:rdbg(main):003> next # use next command to move to the next line
[1, 7] in test.rb
     1|
     2| def greet(word)
     3|   binding.irb
=>   4|   puts "Hello #{word}"
     5| end
     6|
     7| greet("World")
=>#0    Object#greet(word="World") at test.rb:4
  #1    <main> at test.rb:7
irb:rdbg(main):004>

Simultaneously, you maintain access to IRB's commands, such as show_source:

irb:rdbg(main):004> show_source greet

From: test.rb:2

def greet(word)
  binding.irb
  puts "Hello #{word}"
end

More about debug.gem

debug.gem offers many advanced debugging features that simple REPLs can't provide, including:

• Step-debugging
• Frame navigation
• Setting breakpoints with commands
• Thread control
• ...and many more

To learn about these features, please refer to debug.gem's commands list.

In the irb:rdbg session, the help command will also display all commands from debug.gem.

Advantages Over debug.gem's Console

This integration offers several benefits over debug.gem's native console:

1. Access to handy IRB commands like show_source or show_doc.
2. Support for multi-line input.
3. Symbol shortcuts such as @ (whereami) and $ (show_source).
4. Autocompletion.
5. Customizable prompt.

However, there are also some limitations to be aware of:

1. binding.irb doesn't support pre and do arguments like binding.break.
2. As IRB doesn't currently support remote-connection, it can't be used with debug.gem's remote debugging feature.
3. Access to the previous return value via the underscore _ is not supported.

Type Based Completion

IRB's default completion IRB::RegexpCompletor uses Regexp. IRB has another experimental completion IRB::TypeCompletor that uses type analysis.

How to Enable IRB::TypeCompletor

Install ruby/repl_type_completor with:

$ gem install repl_type_completor

Or add these lines to your project's Gemfile.

gem 'irb'
gem 'repl_type_completor', group: [:development, :test]

Now you can use type based completion by:

Running IRB with the --type-completor option

$ irb --type-completor

Or writing this line to IRB's rc-file (e.g. ~/.irbrc)

IRB.conf[:COMPLETOR] = :type # default is :regexp

Or setting the environment variable IRB_COMPLETOR

ENV['IRB_COMPLETOR'] = 'type'
IRB.start

To check if it's enabled, type irb_info into IRB and see the Completion section.

irb(main):001> irb_info
...
# Enabled
Completion: Autocomplete, ReplTypeCompletor: 0.1.0, Prism: 0.18.0, RBS: 3.3.0
# Not enabled
Completion: Autocomplete, RegexpCompletor
...

If you have sig/ directory or rbs_collection.lock.yaml in current directory, IRB will load it.

Advantage over Default IRB::RegexpCompletor

IRB::TypeCompletor can autocomplete chained methods, block parameters and more if type information is available. These are some examples IRB::RegexpCompletor cannot complete.

irb(main):001> 'Ruby'.upcase.chars.s # Array methods (sample, select, shift, size)

irb(main):001> 10.times.map(&:to_s).each do |s|
irb(main):002>   s.up # String methods (upcase, upcase!, upto)

irb(main):001> class User < ApplicationRecord
irb(main):002>   def foo
irb(main):003>     sa # save, save!

As a trade-off, completion calculation takes more time than IRB::RegexpCompletor.

Difference between Steep's Completion

Compared with Steep, IRB::TypeCompletor has some difference and limitations.

[0, 'a'].sample.
# Steep completes intersection of Integer methods and String methods
# IRB::TypeCompletor completes both Integer and String methods

Some features like type narrowing is not implemented.

def f(arg = [0, 'a'].sample)
  if arg.is_a?(String)
    arg. # Completes both Integer and String methods

Unlike other static type checker, IRB::TypeCompletor uses runtime information to provide better completion.

irb(main):001> a = [1]
=> [1]
irb(main):002> a.first. # Completes Integer methods

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.
• IRB_COMPLETOR: Configures IRB's auto-completion behavior, allowing settings for either regexp or type.
• VISUAL: Its value would be used to open files by the edit command.
• EDITOR: Its value would be used to open files by the edit command if VISUAL is unset.
• IRBRC: The file specified would be evaluated as IRB's rc-file.

Documentation

https://ruby.github.io/irb/

Extending IRB

IRB v1.13.0 and later versions allows users/libraries to extend its functionality through official APIs.

For more information, please visit EXTEND_IRB.md.

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.

Set up the environment

1. Fork the project to your GithHub account
2. Clone the fork with git clone git@github.com:[your_username]/irb.git
3. Run bundle install
4. Run bundle exec rake to make sure tests pass locally

Run integration tests

If your changes affect component rendering, such as the autocompletion's dialog/dropdown, you may need to run IRB's integration tests, known as yamatanooroti.

Before running these tests, ensure that you have libvterm installed. If you're using Homebrew, you can install it by running:

brew install libvterm

After installing libvterm, you can run the integration tests using the following commands:

WITH_VTERM=1 bundle install
WITH_VTERM=1 bundle exec rake test test_yamatanooroti

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.