From: Eikichi On <eikichi@...>
Date: 2010-03-02T08:33:23+09:00
Subject: Re: IO.popen with Threads

Thank you very much for your answer, Robert.  Thanks to your help, I 
could start coding. But I have another little problem and I would 
appreciate your opinion.

Here is the code I used:

    class Test
      def initialize(program)
        while isready?(program) && cool?(program)
          program.puts 'start', 'my name is ...'
          # ...
        end
      end

      protected

      def process_command(program, command)
        begin
          rdr = Thread.new { program.read } # alternative: io.readlines
          program.puts "#{command}"
          program.close_write
          rdr.value # joins and fetches the result
        end
      end

      def isready?(program)
        reply = process_command(program, 'isready')
        reply.chomp.match(/yes_i_am_ready$/)
      end

      def cool?(program)
        reply = process_command(program, 'cool')
        reply.chomp.match(/yes_i_am_cool$/)
      end
    end

program = IO.popen("./program", "w+")

a = Test.new(program)
(...)in `write': not opened for writing (IOError)

As we can see, there is an error when I try to send a message to the 
sub-process because of the closure of the stream 
(http://ruby-doc.org/core/classes/IO.html#M002289).

I believe that it is not possible to open again a closed stream.  Do you 
think a good way is to don't close the stream (except at the very end of 
the Ruby script)? or should it be better to change the current code 
structure?

Thanks again for any help.
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