ruby child process with non-buffered output

child.rb

 # give the child process a terminal so output isn't buffered
      @master, slave = PTY.open
      in_clean_environment do
        @pid = ::Process.spawn(
          config.env,
          %Q(bash -c "#{config.command}"),
          :in => slave,
          :out => slave,
          :err => slave,
          :chdir => config.dir,
          :pgroup => true
        )
      end

stolen from https://github.com/zerowidth/ringleader/blob/master/lib/ringleader/process.rb#L117-L129