child_process.rb

require 'rubygems'
require 'eventmachine'

module EventMachine
  module ChildProcess

    def initialize
      @buffer = []
    end

    def receive_data data
      puts "------"
      puts data
      puts "------"
    end

    def unbind
      p get_status
      p get_status.exitstatus
    end

  end

  def EM.spawn cmd, &cb
    EM.popen cmd, ChildProcess do |c|
      p c
    end
  end

  
end


EM.run{
  
  EM.add_periodic_timer(1) {
    print "."
  }

  EM.spawn('ruby long-running-child.rb') do |results|
    puts results
  end
  
  EM.add_timer(15) {
    EM.stop
  }
  
}

long-running-child.rb

require 'rubygems'
require 'eventmachine'

EM.run {
  
  EM.add_periodic_timer(1) {
    puts "tick"
  }
  
  EM.add_timer(10) {
    puts "done"
    EM.stop
  }
  
}

output

#<#<Class:0x500898>:0x500618 @signature="8e0ebeef062bf970d9f5271429d793233", @buffer=[]>
.........------
tick
tick
tick
tick
tick
tick
tick
tick
tick
done
------
#<Process::Status: pid=12937,exited(0)>
0
....