    # File lib/rubygems/commands/cleanup_command.rb, line 29
      def execute
        say "Cleaning up installed gems..."
        primary_gems = {}

        Gem.source_index.each do |name, spec|
          if primary_gems[spec.name].nil? or
             primary_gems[spec.name].version < spec.version then
            primary_gems[spec.name] = spec
          end
        end

        gems_to_cleanup = []

        unless options[:args].empty? then
          options[:args].each do |gem_name|
            specs = Gem.cache.search(/^#{gem_name}$/i)
            specs.each do |spec|
              gems_to_cleanup << spec
            end
          end
        else
          Gem.source_index.each do |name, spec|
            gems_to_cleanup << spec
          end
        end

        gems_to_cleanup = gems_to_cleanup.select { |spec|
          primary_gems[spec.name].version != spec.version
        }

        uninstall_command = Gem::CommandManager.instance['uninstall']
        deplist = Gem::DependencyList.new
        gems_to_cleanup.uniq.each do |spec| deplist.add spec end

        deps = deplist.strongly_connected_components.flatten.reverse

        deps.each do |spec|
          if options[:dryrun] then
            say "Dry Run Mode: Would uninstall #{spec.full_name}"
          else
            say "Attempting to uninstall #{spec.full_name}"

            options[:args] = [spec.name]
            options[:version] = "= #{spec.version}"
            options[:executables] = false

            uninstaller = Gem::Uninstaller.new spec.name, options

            begin
              uninstaller.uninstall
            rescue Gem::DependencyRemovalException,
                   Gem::GemNotInHomeException => e
              say "Unable to uninstall #{spec.full_name}:"
              say "\t#{e.class}: #{e.message}"
            end
          end
        end

        say "Clean Up Complete"
      end