A command/task framework similar to rake and thor built with extendability in mind.
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Boson is a modular command/task framework. Thanks to its rich set of plugins, it differentiates itself from rake and thor by being usable from irb and the commandline, having automated views generated by hirb and allowing libraries to be written as plain ruby. Works with on all major rubies for ruby >= 1.9.2

New Boson

Starting with 1.0, boson has changed significantly. Please read the upgrading doc if you have an older version or if your reading about boson predates 2012.

Boson has been rewritten to have a smaller core (no dependencies) with optional plugins to hook into its various features. The major focus of 1.0 has been to provide an easy way for third-party gems to create their executable and define subcommands with options.


Nicely formatted docs are available here.

Example Executable

For a gem with an executable, bin/cow:

#!/usr/bin/env ruby
require 'boson/runner'

class CowRunner < Boson::Runner
  option :urgent, type: :boolean
  def say(text, options={})
    text.capitalize! if options[:urgent]
    puts text

  def moo
    puts "MOOOO"


You can now execute cow with say and moo subcommands:

$ cow say hungry
$ cow moo
# use say's urgent option
$ cow say hungry -urgent

You'll notice that this syntax is powerful and concise and is very similar to thor's API. Subcommands map to ruby methods and the class represents the executable.

For some examples of executables see vimdb or tag.

Comparison to Thor

Since boson and it's rewrite are both heavily inspired by thor, it makes sense to compare them.

First, what I consider pros boson has over thor. Boson

  • is designed to handle plugins. This means it core parts are extendable by modules and core components like commands can have arbitrary metadata associated with them.
  • has a rich set of plugins. See boson-more.
  • has commands that are easily testable. Whereas thor has options that automagically appear in command methods, boson explicitly passes options to its command method as a hash i.e. MyRunner.new.subcommand(arg, verbose: true). This also allows commands to just be called as ruby, with no magic to consider.
  • supports custom-user option types i.e. creating a Date option type. See Boson::Options.
  • supports custom method decorators i.e. methods like desc that add functionality to a command. While boson supports option, options, desc and config out of the box, users can create their own.
  • automatically creates usage for your subcommand. With thor you need to manually define your usage with desc: desc "SOME USAGE", "SOME DESCRIPTION"
  • is lenient about descriptions. Describe commands at your leisure. With thor you must define a desc.
  • has no blacklist for command names while thor has a blacklist due to its design. With boson you can even name commands after Kernel method names but tread with caution in your own Runner class.
  • allows for user-defined default global options (i.e. --help) and commands (i.e. help). This means that with a plugin you could have your own additional default options and commands shared across executables. See the extending section below.
  • allows default help and command help to be overridden/extended by subclassing Runner.display_help and Runner.display_command_help respectively.
  • provides an optional custom rc file for your executable. Simply set ENV['BOSONRC'] to a path i.e. ~/.myprogramrc. This rc file loads before any command processing is done, allowing for users to extend your executable easily i.e. to add more subcommands. For an example, see vimdb.

Now for pros thor has over boson. Thor

  • is widely used and thus has been community QAed thoroughly.
  • supports generators as a major feature.
  • is more stable as its feature set is mostly frozen.
  • is used by rails and thus is guaranteed support for some time.
  • supports ruby 1.8.7.
  • can conveniently define an option across commands using class_option. boson may add this later.
  • TODO: I'm sure there's more

Converting From Thor

  • Change your requires and subclass from Boson::Runner instead of Thor.
  • Delete the first argument from desc. Usage is automatically created in boson.
  • Rename method_option to option
  • For options with a type option, make sure it maps to a symbol i.e. :array or :boolean. If left a string, the option will be interpreted to be a string option with that string as a default.
  • class_option doesn't exist yet but you can emulate it for now by defining your class option in a class method and then calling your class method before every command. See vimdb for an example.

Writing Plugins

A Boson plugin is a third-party library that extends Boson through its extension API. Any Boson class/module that includes or extends a module named API or APIClassMethods provides an extension API. Examples of such classes are Boson::BareRunner, Boson::Command, Boson::Inspector and Boson::Library. As an example, let us extend what any boson-based executable does first, extend Boson::BareRunner.start:

module Boson
  module CustomStartUp
    def start(*)
      # additional startup

Boson::BareRunner.extend Boson::CustomStartUp

Notice that extend was used to extend a class method. To extend an instance method you would use include. Also notice that you use super in an overridden method to call original functionality. If you don't, you're possibly overridden existing functionality, which is fine as long as you know what you are overriding.

If you want to gemify your plugin, name it boson-plugin_name and put it under lib/boson/plugin_name. The previous example would go in lib/boson/custom_startup.rb. To use your plugin, a user can simply require your plugin in their executable.

For many plugin examples, see boson-more.

Using a Plugin

To use a plugin, just require it. For an executable:

require 'boson/runner'
require 'boson/my_plugin'


For the boson executable, just require the plugins in ~/.bosonrc.

Extending Your Executables

Boson allows for custom default options and commands. This means you can add your own defaults in a plugin and use them across your executables.

To add a custom default command, simply reopen Boson::DefaultCommandsRunner:

class Boson::DefaultCommandsRunner
  desc "whoomp"
  def whoomp
    puts "WHOOMP there it is!"

To add a custom global option, add to Boson::Runner::GLOBAL_OPTIONS:

  verbose: {type: :boolean, desc: "Verbose description of loading libraries"}

Custom global options are defined in the same format as options for a command.


Please report them on github. If the issue is about upgrading from old boson, please file it in boson-more.


See here


Motivation for the new boson is all the damn executables I'm making.


Boson stands on the shoulders of these people and their ideas:

  • Contributors: @mirell, @martinos, @celldee, @zhando
  • Yehuda Katz for Thor and its awesome option parser (Boson::OptionParser).
  • Daniel Berger for his original work on thor's option parser.
  • Chris Wanstrath for inspiring Boson's libraries with Rip's packages.