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Thor is a toolkit for building powerful command-line interfaces.

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Thor is a simple and efficient tool for building self-documenting command line utilities. It removes the pain of parsing command line options, writing "USAGE:" banners, and can also be used as an alternative to the Rake build tool. The syntax is Rake-like, so it should be familiar to most Rake users.


$ gem install thor


$ gem install wycats-thor -s


Map options to a class. Simply create a class with the appropriate annotations and have options automatically map to functions and parameters.


class App < Thor                                                 # [1]
  map "-L" => :list                                              # [2]

  desc "install APP_NAME", "install one of the available apps"   # [3]
  method_options :force => :boolean, :alias => :string           # [4]
  def install(name)
    user_alias = options[:alias]
    if options.force?
      # do something
    # other code

  desc "list [SEARCH]", "list all of the available apps, limited by SEARCH"
  def list(search="")
    # list everything

Thor automatically maps commands as such:

thor app:install myname --force

That gets converted to:"myname")
# with {'force' => true} as options hash
  1. Inherit from Thor to turn a class into an option mapper.
  2. Map additional non-valid identifiers to specific methods. In this case, convert -L to :list
  3. Describe the method immediately below. The first parameter is the usage information, and the second parameter is the description.
  4. Provide any additional options that will be available the instance method options.

Types for method_options

  • :boolean - is parsed as --option or --option=true
  • :string - is parsed as --option=VALUE
  • :numeric - is parsed as --option=N
  • :array - is parsed as --option=one two three
  • :hash - is parsed as --option=name:string age:integer

Besides, method_option allows a default value to be given. Examples:

method_options :force => false
#=> Creates a boolean option with default value false

method_options :alias => "bar"
#=> Creates a string option with default value "bar"

method_options :threshold => 3.0
#=> Creates a numeric option with default value 3.0

You can also supply :option => :required to mark an option as required. The type is assumed to be string. If you want a required hash with default values as option, you can use method_option which uses a more declarative style:

method_option :attributes, :type => :hash, :default => {}, :required => true

All arguments can be set to nil (except required arguments), by suppling a no or skip variant. For example:

thor app name --no-attributes

In previous versions, aliases for options were created automatically, but now they should be explicit. You can supply aliases in both short and declarative styles:

method_options %w( force -f ) => :boolean


method_option :force, :type => :boolean, :aliases => "-f"

You can supply as many aliases as you want.

NOTE: Type :optional available in Thor 0.9.0 was deprecated. Use :string or :boolean instead.


By default, your Thor tasks are invoked using Ruby namespace. In the example above, tasks are invoked as:

thor app:install name --force

However, you could namespace your class as:

module Sinatra
  class App < Thor
    # tasks

And then you should invoke your tasks as:

thor sinatra:app:install name --force

If desired, you can change the namespace:

module Sinatra
  class App < Thor
    namespace :myapp
    # tasks

And then your tasks should be invoked as:

thor myapp:install name --force


Thor comes with a invocation-dependency system as well, which allows a task to be invoked only once. For example:

class Counter < Thor
  desc "one", "Prints 1, 2, 3"
  def one
    puts 1
    invoke :two
    invoke :three

  desc "two", "Prints 2, 3"
  def two
    puts 2
    invoke :three

  desc "three", "Prints 3"
  def three
    puts 3

When invoking the task one:

thor counter:one

The output is "1 2 3", which means that the three task was invoked only once.
You can even invoke tasks from another class, so be sure to check the documentation.


Thor has a special class called Thor::Group. The main difference to Thor class is that it invokes all tasks at once. The example above could be rewritten in Thor::Group as this:

class Counter < Thor::Group
  desc "Prints 1, 2, 3"

  def one
    puts 1

  def two
    puts 2

  def three
    puts 3

When invoked:

thor counter

It prints "1 2 3" as well. Notice you should describe (using the method desc) only the class and not each task anymore. Thor::Group is a great tool to create generators, since you can define several steps which are invoked in the order they are defined (Thor::Group is the tool use in generators in Rails 3.0).

Besides, Thor::Group can parse arguments and options as Thor tasks:

class Counter < Thor::Group
  # number will be available as attr_accessor
  argument :number, :type => :numeric, :desc => "The number to start counting"
  desc "Prints the 'number' given upto 'number+2'"

  def one
    puts number + 0

  def two
    puts number + 1

  def three
    puts number + 2

The counter above expects one parameter and has the folling outputs:

thor counter 5
# Prints "5 6 7"

thor counter 11
# Prints "11 12 13"

You can also give options to Thor::Group, but instead of using method_option and method_options, you should use class_option and class_options. Both argument and class_options methods are available to Thor class as well.


Thor comes with several actions which helps with script and generator tasks. You might be familiar with them since some came from Rails Templates. They are: say, ask, yes?, no?, add_file, remove_file, copy_file, template, directory, inside, run, inject_into_file and a couple more.

To use them, you just need to include Thor::Actions in your Thor classes:

class App < Thor
  include Thor::Actions
  # tasks

Some actions like copy file requires that a class method called source_root is defined in your class. This is the directory where your templates should be placed. Be sure to check the documentation on actions.


A great use for Thor is creating custom generators. Combining Thor::Group, Thor::Actions and ERB templates makes this very easy. Here is an example:

class Newgem < Thor::Group
  include Thor::Actions

  # Define arguments and options
  argument :name
  class_option :test_framework, :default => :test_unit

  def self.source_root

  def create_lib_file
    template('templates/', "#{name}/lib/#{name}.rb")

  def create_test_file
    test = options[:test_framework] == "rspec" ? :spec : :test
    create_file "#{name}/#{test}/#{name}_#{test}.rb"

  def copy_licence
    if yes?("Use MIT license?")
      # Make a copy of the MITLICENSE file at the source root
      copy_file "MITLICENSE", "#{name}/MITLICENSE"
      say "Shame on you…", :red

Doing a thor -T will show how to run our generator. It should read: thor newgem NAME. This shows that we have to supply a NAME argument for our generator to run.

The create_lib_file uses an ERB template. This is what it looks like:

class <%= name.capitalize %>

The arguments that you set in your generator will automatically be passed in when template gets called. Be sure to read the documentation for more options.

Running the generator with thor newgem devise will create two files: "devise/lib/devise.rb", and "devise/test/devise_test.rb". The user will then be asked (via a prompt by the yes? method) whether or not they would like to copy the MIT License. If you want to change the test framework, you can add the option: thor newgem devise --test-framework=rspec

This will generate two files - "devise/lib/devise.rb" and "devise/spec/devise_spec.rb".

Further Reading

Thor offers many scripting possibilities beyond these examples. Be sure to read through the documentation and specs to get a better understanding of the options available.


Released under the MIT License. See the LICENSE file for further details.

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