    # File lib/rubygems/commands/install_command.rb, line 45
      def execute
        if options[:include_dependencies] then
          alert "`gem install -y` is now default and will be removed"
          alert "use --ignore-dependencies to install only the gems you list"
        end

        installed_gems = []

        ENV.delete 'GEM_PATH' if options[:install_dir].nil? and RUBY_VERSION > '1.9'

        install_options = {
          :env_shebang => options[:env_shebang],
          :domain => options[:domain],
          :force => options[:force],
          :format_executable => options[:format_executable],
          :ignore_dependencies => options[:ignore_dependencies],
          :install_dir => options[:install_dir],
          :security_policy => options[:security_policy],
          :wrappers => options[:wrappers],
          :bin_dir => options[:bin_dir],
          :development => options[:development],
        }

        exit_code = 0

        get_all_gem_names.each do |gem_name|
          begin
            inst = Gem::DependencyInstaller.new install_options
            inst.install gem_name, options[:version]

            inst.installed_gems.each do |spec|
              say "Successfully installed #{spec.full_name}"
            end

            installed_gems.push(*inst.installed_gems)
          rescue Gem::InstallError => e
            alert_error "Error installing #{gem_name}:\n\t#{e.message}"
            exit_code |= 1
          rescue Gem::GemNotFoundException => e
            alert_error e.message
            exit_code |= 2
    #      rescue => e
    #        # TODO: Fix this handle to allow the error to propagate to
    #        # the top level handler.  Examine the other errors as
    #        # well.  This implementation here looks suspicious to me --
    #        # JimWeirich (4/Jan/05)
    #        alert_error "Error installing gem #{gem_name}: #{e.message}"
    #        return
          end
        end

        unless installed_gems.empty? then
          gems = installed_gems.length == 1 ? 'gem' : 'gems'
          say "#{installed_gems.length} #{gems} installed"
        end

        # NOTE: *All* of the RI documents must be generated first.
        # For some reason, RI docs cannot be generated after any RDoc
        # documents are generated.

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

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

        if options[:test] then
          installed_gems.each do |spec|
            gem_spec = Gem::SourceIndex.from_installed_gems.search(spec.name, spec.version.version).first
            result = Gem::Validator.new.unit_test(gem_spec)
            if result and not result.passed?
              unless ask_yes_no("...keep Gem?", true) then
                Gem::Uninstaller.new(spec.name, :version => spec.version.version).uninstall
              end
            end
          end
        end

        raise Gem::SystemExitException, exit_code
      end