Mission: Easy custom autocompletion for arguments, methods and beyond. Accomplished for irb and any other readline-like console environments.
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Bond is on a mission to improve autocompletion in ruby, especially for irb/ripl. Aside from doing everything irb's can do and fixing its quirks, Bond can autocomplete argument(s) to methods, uniquely completing per module, per method and per argument. Bond brings ruby autocompletion closer to bash/zsh as it provides a configuration system and a DSL for creating custom completions and completion rules. With this configuration system, users can customize their autocompletions and share it with others. Bond can also load completions that ship with gems. Bond is able to offer more than irb's completion since it uses the full line of input when completing as opposed to irb's last-word approach.


To use bond with Readline (version >= 5.6 recommended) or JLine for JRuby users, install the gem with:

gem install bond

To use bond with a pure ruby readline i.e. Windows users or users without Readline:

gem install bond rb-readline -- --without-readline

To use bond without readline support (and presumably use your own readline plugin):

gem install bond -- --without-readline


If you're using ripl instead of irb, bond is already setup.

To start off, replace irb's completion (require 'irb/completion') with Bond's enhanced version in your irbrc:

require 'bond'
# For users using a pure ruby readline
Bond.start :readline => :ruby

This setup gives you more consistent method completion on any object, customizable completions and argument completion of some 80+ methods including Hash#[], Kernel#system, Kernel#require and some Rails methods.

Method Argument Completion

By default, Bond autocompletes arguments for a number of core methods:

$ ripl
# require completes gems and anything in $LOAD_PATH
>> require 'rb[TAB]
rbconfig.rb          rbconfig/
>> require 'rbconfig
>> require 'rbconfig.rb'

# hash methods can complete their keys
>> CONFIG::CONFIG['mandir'
>> CONFIG::CONFIG['mandir']


# array methods can complete their elements
>> %w{ab bc cd de}.delete '[TAB]
ab  bc  cd  de
>> %w{ab  bc  cd  de}.delete 'a[TAB]
>> %w{ab  bc  cd  de}.delete 'ab'

# system can complete shell commands
>> system 'ec[TAB]
>> system 'echo
>> system 'echo'

Bond also comes with some basic Rails completions, mostly for attributes/columns of models:

$ script/console
>> Url.column_names
=> ["id", "name", "description", "created_at", "updated_at"]
>> Url.create :n[TAB]
>> Url.create :name
>> Url.first.update_attribute :d[TAB]
>> Url.first.update_attribute :description

To see more methods whose arguments can be completed:

>> puts Bond.list_methods

Multiple Arguments

Every time a comma appears after a method, Bond starts a new completion. This allows a method to complete multiple arguments. Each argument can be have a unique set of completions since a completion action is aware of what argument it is currently completing. Take for example the completion for Object#send:

>> Bond.send :me[TAB]
>> Bond.send :method
>> Bond.send :method, [TAB]
agent       complete    config      recomplete  spy         start
>> Bond.send :method, :a[TAB]
>> Bond.send :method, :agent
=> #<Method: Module#agent>

Notice the arguments were completed differently: the first completing for Bond.send and the second for Bond.method. The second argument was only able to complete because there's a completion for Module#method. Using Object#send it's possible to use completions defined for private methods i.e. Module#remove_const:

>> Bond.send :remove_const, :A[TAB]
:Agent            :AnywhereMission
>> Bond.send :remove_const, :Ag[TAB]
>> Bond.send :remove_const, :Agent

Since Bond uses a comma to delimit completions, methods whose last argument is a hash can have their hash keys autocompleted. Revisiting the above Rails example:

>> Url.create :n[TAB]
>> Url.create :name
>> Url.create :name=>'example.com', :d[TAB]
>> Url.create :name=>'example.com', :description
>> Url.first.update_attributes :d[TAB]
>> Url.first.update_attributes :description
>> Url.first.update_attributes :description=>'zzz', :u[TAB]
>> Url.first.update_attributes :description=>'zzz', :updated_at

Creating Completions

Bond's completion resembles bash/zsh's. When Bond.start is called, Bond looks up completion files in multiple places: ~/.bondrc and ~/.bond/completions/*.rb. Here's how bash and bond completion definitions compare in their config files:

# Bash
complete -W "one two three" example
complete -F _example example

# Bond
complete(:method=>'example') { %w{one two three} }
complete(:method=>'example', :action=>'_example')

To read up on the wealth of completion types one can make, see the docs for Bond.complete.

Creating Argument Completions for Methods

While the above method completion was a static list, most completions will dynamically generate completions based on the method's receiver (object). Let's look at such an example with Hash#[] :

complete(:method=>"Hash#[]") {|e| e.object.keys }

As you can see, the currently typed object is available as the :object attribute of the block's argument, a Bond::Input object. This object can offer other useful attributes describing what the user has typed. For example, the :argument attribute holds the current argument number being completed. Here's a completion that uses this attribute to complete differently for the first argument and remaining arguments:

complete(:method=>'example') {|e| e.argument > 1 ? %w{verbose force noop} : %w{one two three} }

Creating Other Completions

First you should know Bond works: A user creates completion missions with Bond.start and its config files (which are just Bond.complete calls). When a user autocompletes, Bond.agent looks up missions in the order they were defined and completes with the first one that matches. The exception to this ordering are :method completions.

To create a completion, Bond.complete needs a regexp to match the user input and an action to generate completions when it matches. If the completion isn't working, use Bond.spy to see which completion is executing. If a completion needs to be placed before existing completions, use the :place option.

Irb's Incorrect Completions

There are a number of incorrect completions irb gives for object methods. Bond fixes all of the ones described below.

Irb completes anything surrounded with '{}' the same:

$ irb
>> proc {}.c[TAB]
}.call     }.class    }.clear    }.clone    }.collect
>> %w{ab bc}.c[TAB]
}.call     }.class    }.clear    }.clone    }.collect
>> %r{ab bc}.c[TAB]
}.call     }.class    }.clear    }.clone    }.collect
>> {}.c[TAB]
}.call     }.class    }.clear    }.clone    }.collect
>> {}.call
NoMethodError: undefined method `call' for {}:Hash
        from (irb):1

There are a number of cases where irb gives a default completion because it doesn't know what else to do.

 # The default completion
 >> self.[TAB]
 Display all 496 possibilities? (y or n)

 # And all of these cases are apparently the same:
 >> nil.[TAB]
 Display all 496 possibilities? (y or n)
 >> false.[TAB]
 Display all 496 possibilities? (y or n)
 >> true.[TAB]
 Display all 496 possibilities? (y or n)
 # Regular expressions with spaces
 >> /man oh man/.[TAB]
 Display all 496 possibilities? (y or n)
 # Grouped expressions
>> (3 + 4).[TAB]
Display all 496 possibilities? (y or n)

# Nested hashes and arrays
>> {:a=>{:a=>1}}.[TAB]
Display all 496 possibilities? (y or n)
>> [[1,2], [3,4]].[TAB]
Display all 496 possibilities? (y or n)

# Any object produced from a method call
>> 'awesome'.to_sym.[TAB]
Display all 496 possibilities? (y or n)
>> :dude.to_s.[TAB]
Display all 496 possibilities? (y or n)

Ranges don't get much love

>> (2..4).[TAB]
# Nothing happens


If on a Mac and using Editline as a Readline replacement (Readline::VERSION =~ /editline/i), Bond will probably not work consistently. I strongly recommend switching to the official Readline. If using rvm, this post has good instructions for reinstalling ruby with the official Readline.


  • Csaba Hank for providing the C extension which Bond uses to read Readline's full buffer.

  • Takao Kouji for commiting this Readline enhancement to ruby 1.9.2.

  • pd for compatibility with emacs' inf-ruby mode.

  • timcharper for improving extconf.rb.

  • headius for jruby support


Please report them on github.


See here



  • Make completion actions more synonymous with argument types.

  • Cache expensive completion actions.

  • Ensure completions work when there is additional, unrelated text to the right of a completion.