execute (Gem::Commands::UpdateCommand)

    # File lib/rubygems/commands/update_command.rb, line 47
      def execute
        hig = {}

        if options[:system] then
          say "Updating RubyGems"

          unless options[:args].empty? then
            fail "No gem names are allowed with the --system option"
          end

          rubygems_update = Gem::Specification.new
          rubygems_update.name = 'rubygems-update'
          rubygems_update.version = Gem::Version.new Gem::RubyGemsVersion
          hig['rubygems-update'] = rubygems_update

          options[:user_install] = false
        else
          say "Updating installed gems"

          hig = {} # highest installed gems

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

        gems_to_update = which_to_update hig, options[:args]

        updated = []

        installer = Gem::DependencyInstaller.new options

        gems_to_update.uniq.sort.each do |name|
          next if updated.any? { |spec| spec.name == name }
          success = false

          say "Updating #{name}"
          begin
            installer.install name
            success = true
          rescue Gem::InstallError => e
            alert_error "Error installing #{name}:\n\t#{e.message}"
            success = false
          end

          installer.installed_gems.each do |spec|
            updated << spec
            say "Successfully installed #{spec.full_name}" if success
          end
        end

        if gems_to_update.include? "rubygems-update" then
          Gem.source_index.refresh!

          update_gems = Gem.source_index.find_name 'rubygems-update'

          latest_update_gem = update_gems.sort_by { |s| s.version }.last

          say "Updating RubyGems to #{latest_update_gem.version}"
          installed = do_rubygems_update latest_update_gem.version

          say "RubyGems system software updated" if installed
        else
          if updated.empty? then
            say "Nothing to update"
          else
            say "Gems updated: #{updated.map { |spec| spec.name }.join ', '}"

            if options[:generate_ri] then
              updated.each do |gem|
                Gem::DocManager.new(gem, options[:rdoc_args]).generate_ri
              end

              Gem::DocManager.update_ri_cache
            end

            if options[:generate_rdoc] then
              updated.each do |gem|
                Gem::DocManager.new(gem, options[:rdoc_args]).generate_rdoc
              end
            end
          end
        end
      end