Add a CLI to any class instantly
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Executable is to the commandline, what ActiveRecord is the database. You can think of Executable as a COM, a Command-line Object Mapper, just as ActiveRecord is an ORM (Object Relational Mapper). Any class mixing in Executable or subclassing Executable::Command can define a complete command line tool using nothing more than Ruby's standard syntax. No special DSL is required.


  • Easy to use, just mixin or subclass.
  • Define #call to control the command procedure.
  • Public writers become options.
  • Namespace children become subcommands.
  • Or easily dispatch subcommands to public methods.
  • Generate help in plain text or markdown.


  • Ruby 1.9+ only.
  • Help doesn't handle aliases well (yet).


CLIs can be built by using a Executable as a mixin, or by subclassing Executable::Command. Methods seemlessly handle command-line options. Writer methods (those ending in '=') correspond to options and query methods (those ending in '?') modify them to be boolean switches.

For example, here is a simple "Hello, World!" commandline tool.

    require 'executable'

    class HelloCommand
      include Executable

      # Say it in uppercase?
      def loud=(bool)
        @loud = bool

      def loud?

      # Show this message.
      def help!
      alias :h! :help!

      # Say hello.
      def call(name)
        name = name || 'World'
        str  = "Hello, #{name}!"
        str  = str.upcase if loud?
        puts str

To make the command available on the command line, add an executable to your project calling the #execute or #run methods.

    #!usr/bin/env ruby
    require 'hello.rb'

If we named this file hello, set its execute flag and made it available on our systems $PATH, then:

    $ hello
    Hello, World!

    $ hello John
    Hello, John!

    $ hello --loud John

Executable can also generate help text for commands.

    $ hello --help
    USAGE: hello [options]

    Say hello.

    --loud      Say it in uppercase?
    --help      Show this message

If you look back at the class definition you can see it's pulling comments from the source to provide descriptions. It pulls the description for the command itself from the #call method.

Basic help like this is fine for personal tools, but for public facing production applications it is desirable to utilize manpages. To this end, Executable provides Markdown formatted help as well. We can access this, for example, via The idea with this is that we can save the output to man/hello.ronn or copy it the top of our bin/ file, edit it to perfection and then use tools such a ronn, binman or md2man to generate the manpages. What's particularly cool about Executable, is that once we have a manpage in the standard man/ location in our project, the #show_help method will use it instead of the plain text.

For a more detailed example see QED, API documentation and, in particular, the Wiki.


Install with RubyGems in the usual fashion.

    $ gem install executable


Executable is a Rubyworks project. As such it largely uses in-house tools for development.

Submitting Patches

If it is a very small change, just pasting it to an issue is fine. For anything more than this please send us a traditional patch, but even better use Github pull requests. Good contributions have the following:

  • Well documented code following the conventions of the project.
  • Clearly written tests with good test coverage written using the project's chosen test framework.
  • Use of a git topic branch to keep the change set well isolated.

The more of these bullet points a pull request covers, the more likely and quickly it will be accepted and merged.


QED and Microtest are used for this project. To run the QED demos just run the qed command, probably with bundler, so bundle exec qed. And to run the microtests you can use rubytest test/, again with bundler, bundle exec rubytest test/.

Getting In Touch

For direct dialog we have an IRC channel, #rubyworks on freenode. But it's not always manned, so a mailing list is also available. Of course these days, the GitHub issues page is generally the place get in touch for anything specific to this project.


Executable is copyrighted open source software.

Copyright (c) 2008 Rubyworks (BSD-2-Clause)

It can be distributed and modified in accordance with the BSD-2-Clause license.

See LICENSE.txt for details.