# File lib/aws/core/client.rb, line 585
      def user_agent_string
        engine = (RUBY_ENGINE rescue nil or "ruby")
        user_agent = "%s aws-sdk-ruby/#{VERSION} %s/%s %s" %
          [config.user_agent_prefix, engine, RUBY_VERSION, RUBY_PLATFORM]
        user_agent.strip!
        if AWS.memoizing?
          user_agent << " memoizing"
        end
        user_agent
      end