gistfile1.rb

#!/usr/bin/ruby                                                                                                                                                                                           

require 'rubygems'
require 'eventmachine'

$done = false
module FdWatcher
  def notify_readable
    puts "readable event"
    begin
      buf = @io.sysread(4096)
      puts "saw #{buf.length} bytes of data: '#{buf}'"
    rescue SystemCallError, EOFError => ex
      puts "DEBUG: saw read exception #{ex}"
      detach
      $done = true
    rescue => ex
      puts "else #{ex.inspect}"
    end
  end
end

class FdClass < EventMachine::Connection
  include FdWatcher
end

puts "hello world"

def add_subprocess(cmd)
  stdin_rd, stdin_wr = IO.pipe
  stdout_rd, stdout_wr = IO.pipe
  stderr_rd, stderr_wr = IO.pipe
  pid = fork
  if not pid.nil?
    # parent                                                                                                                                                                                              
    #EM.watch(stdin_wr, FdClass) { |c| c.notify_writable = true }                                                                                                                                         
    EM.watch(stdout_rd, FdClass) { |c| c.notify_readable = true }
  else
    STDIN.reopen(stdin_rd)
    STDOUT.reopen(stdout_wr)
    STDERR.reopen(stderr_wr)
    exec(*cmd)
  end
end

EM.run {
  EM.schedule {
    puts "hello scheduled, starting up"
    add_subprocess(%w{ /bin/echo -n hello world child process })
  }
  EM.add_periodic_timer(0.5) {
    puts "TIMER! done: #{$done}"
    if $done
      EM.stop_event_loop
    end
  }
}