With a command line Ruby application using Thor for the option parsing I want to be able to run:

$ thor_app --version
> thor_app version 1.0.0

Create a boolean class option, which does not belong to a task, that can be referenced by other tasks. The often used example for a class option is -v verbose, as all tasks can use this to determine how noisy they should be.

Then create a ‘version’ task and make it the default task, so when no task is defined the version task is ran and can react to the –version flag (class option).

class CLI < Thor
  #include Thor::Actions
  class_option :version, :type => :boolean

  desc "version", "Show thor_app version"
  def version
    if options[:version]
      puts "thor_app version #{find_version}"
  default_task :version

  no_tasks do
    def find_version
      ## Method can be replaced to look up VERSION

This is based on my SO Question.