# File lib/rfilter/deliver.rb, line 155
    def deliver_filter(message, *command)
      begin
        to_r, to_w = IO.pipe
        from_r, from_w = IO.pipe
        if pid = fork
          # parent
          to_r.close
          from_w.close
          writer = Thread::new {
            message.each { |line|
              to_w << line
              to_w << "\n" unless line[-1] == ?\n
            }
            to_w.close
          }
          yield from_r
        else
          # child
          begin
            to_w.close
            from_r.close
            STDIN.reopen(to_r)
            to_r.close
            STDOUT.reopen(from_w)
            from_w.close
            exec(*command)
          ensure
            exit!
          end
        end
      ensure
        writer.kill if writer and writer.alive?
        [ to_r, to_w, from_r, from_w ].each { |io|
          if io && !io.closed?
            begin
              io.close
            rescue Errno::EPIPE
            end
          end
        }
      end
      Process.waitpid2(pid, 0)[1]
    end