thor.rb

$ bundle gem myapp; cd myapp
$ mkdir bin
$ vim bin/myapp

  #!/usr/bin/env ruby
  
  require 'pathname'
  lib = Pathname.new(__FILE__).dirname.join('..', 'lib').expand_path
  $LOAD_PATH.unshift lib.to_s
  
  require 'myapp'

  Myapp::CLI.start

$ vim lib/myapp.rb

  require "myapp/version"
  require "myapp/cli"
  
  module Myapp
    # Your code goes here...
  end

$ vim lib/myapp/cli.rb

  require 'thor'
  
  module Myapp
    class CLI < Thor
      desc 'list', 'list something'
      def list
        puts 'write something to list'
      end
    end
  end

$ vim myapp.gemspec
..snip..
  gem.description   = ["something write here"]
  gem.summary       = ["command to do something"]
..snip..
  gem.add_dependency('thor', '~> 0.17.0')

$ bundle install
$ bundle exec ruby bin/myapp
Tasks:
  myapp help [TASK]  # Describe available tasks or one specific task
  myapp list         # list something

$ git add -A
$ git ci -m 'Initial'
$ gem build myapp.gemspec # => ./myapp-0.0.1.gem