Idle Hacking

Pipes are a really simple way to send messages from one process to another.

MAX_READ = 4

rd, wd = IO.pipe

pid = fork do 
  wd.close

  msg_buffer = ""
  c = 0

  while( 1 )
    # select on the read end of the pipe
    ready = IO.select( [rd], nil, nil, 1 )
    if ready
      ready[0].each do|io|
        msg_buffer << begin
          io.read_nonblock(MAX_READ)
        rescue EOFError
          puts "the pipe was unexpectidly closed??"
          exit
        rescue Object => e
          STDERR.puts "failed with" + e.message + "\n" + e.backtrace("\n")
        end

        last_is_complete = msg_buffer.match(/\n\n$/)
        messages = msg_buffer.split("\n\n")

        # the last msg is not complete
        if !last_is_complete
          msg_buffer = messages.pop
        else
          msg_buffer = "" # reset the msg_buffer we're reading everything
        end

        messages.each do|msg|
          puts msg
          c += 1
        end

        puts c

      end
    end
  end
end

rd.close

count = 10
while( count > 0 )
  wd.write( "hello\n\nhello\n\nhello\n\n" )
  wd.write( "hello\n\n" )
  wd.write( "hello\n\nhello\n\nhello\n\n" )
  wd.write( "hello\n\n" )
  wd.write( "hello\n\n" )
  sleep 0.1
  count -= 1
end
wd.close