From: Albert <none@...>
Date: 2005-04-18T10:29:43+09:00
Subject: Problems with popen3

I'm trying to wrap Ruby around a program, interfacing with it via 
stdin/stdout. Say I have the following C program:

#include <stdio.h>
int main() {
  const char buf[128];
  while (1) {
    printf("enter: ");
    gets(buf);
    printf("result: %s\n", buf);
  }

  return 0;
}


And the following ruby script:

#!/usr/bin/env ruby
require 'open3'
gin, gout, gerr = Open3.popen3('./mytest.exe')
gout.sync = true
STDOUT.sync = true

while line = gout.gets
    puts 'recv:' + line
end

I expect it to print "recv: enter: " but it doesn't. At least on ruby 
1.8.2 under cygwin under windows, Ruby blocks on the gout.gets. I've 
tried adding STDOUT.sync = true and gout.sync = true but that doesn't 
help. I tested it on Fedora/Ruby 1.8.2 and it doesn't seem to work there 
either. Am I doing something wrong, or is this just a limitation of 
popen?