From: Phlip <phlip_cpp@...>
Date: 2002-09-06T14:29:52+09:00
Subject: How to have a conversation with popen

Rubies:

The popen (and popen3) documentation and discussions in the 'net archives 
deal with opening a program and only reading from it.

I want to have a QA session. So here's a Ruby program (save it as "qa.rb") 
that asks a question, collects an answer, and prints it:

    print 'question? '
    STDOUT.flush()
    answer = gets()
    puts answer
    STDOUT.flush()

Now that has excess flushes, but they don't seem to help. Here's a program 
that tries to run that program, answer its question, and collect the 
bounced answer. It has excess flushes too. It also cheats by knowing the 
length of the question. My target program can cheat like this too:

    require 'fcntl'

    pipe = IO.popen( "ruby qa.rb", "r+" )
    # pipe.close_write()
    pipe.fcntl(Fcntl::F_SETFL, Fcntl::O_NONBLOCK)


    def absorb pipe
        contents = ''

        loop do
            begin
                nu = pipe.readchar()
            rescue
                nu = nil
            end

            contents += nu.chr() if nu != nil

            break if contents.size() > 9
        end

        puts contents
    end

    absorb pipe

    pipe.write('yo\n')
    pipe.flush()

    absorb pipe


Please observe I'm not asking how to popen into the ruby executable itself. 
My ultimate target is a binary executable, so telling me how to change the 
options of the inner ruby won't help.

-- 
  Phlip
       http://www.greencheese.org/LucidScheming
  --  Got in trouble at StarBucks. I tried to order
        "A double latte mocha and a body piercing."  --