Using trollop for subcommands; delegates to other command script

bel2.rb

#!/usr/bin/env ruby
require 'bel'
require 'bel/vendor/trollop'

VERSION_BANNER = <<-VERSION
bel #{BEL::VERSION}
Copyright (C) 2015 OpenBEL
Apache License, Version 2.0, January 2004
http://www.apache.org/licenses/
VERSION

module BEL
  module Commands

    # Defines the outer command. Stops on unknown arguments which may
    # be a sub command.
    class BelCommand

      def run
        Trollop::options do
          synopsis "A set of commands to process BEL knowledge."
          usage    "Usage: #{__FILE__} [OPTIONS]... COMMAND"
          version  ::VERSION_BANNER

          opt      :verbose, 'Verbose output.',
                   :long  => :verbose,
                   :short => :v
          stop_on_unknown
        end

        BelCommand.fail_unless_subcommand
      end

      # If +ARGV+ is empty after the call to +Trollop::options+ then a
      # sub command argument was not given. +Trollop::educate+ will then
      # show help.
      def self.fail_unless_subcommand
        Trollop::educate if ARGV.empty?
      end
    end

    # The +parse+ command.
    class ParseCommand

      def run
        
        # Parse the expected options.
        parsed_options =
          Trollop::options do
            synopsis "Shows parse of BEL script."
            usage    "Usage: #{__FILE__} [OPTIONS]... parse --bel [FILE]"

            opt      :bel,       'The BEL script to parse and output. If not provided the default is to read from standard in (STDIN).',
                     :type    => String,
                     :long    => :bel,
                     :short   => :b,
                     :default => nil
          end

        # If the --bel option was specified, unshift back to ARGV
        # and call +bel_parse.rb+.
        if parsed_options[:bel]
          binding.pry
          ARGV.concat(['--bel', parsed_options[:bel]])
        else
          Trollop::educate if !ARGV.empty?
        end

        require_relative 'bel_parse'
      end
    end
  end
end

# ARGV, now chewed in sequence.

# First break off the global options; stopping on unknown args.
BEL::Commands::BelCommand.new.run

# Assume unknown arg is a sub command and compute sub command
# class constant.
sub_command = ARGV.shift
sub_class   = :"#{sub_command.capitalize}Command"

# Call sub command if the constant exists otherwise provide help.
if BEL::Commands.const_defined?(sub_class)
  BEL::Commands.const_get(sub_class).new.run
else
  $stderr.puts "error: The command #{sub_command} is not valid.\n\n"
  Trollop::educate
end

Nice example. Do you consume any of the BelCommand class global options in another command?