Ruby: check for zombie children processes, kill them, and spawn a new parent process

I've recently been working on phantomjs code that can time out and leave behind zombie children processes. Here's a method I created to check for child threads, kill the parent to remove child processes, and spawn a new instance of the parent process.

def kill_zombie_children

  # process id of current thread
  parent_pid = Process.pid

  # get a list of processes and children
  process_output = `ps -eo pid,ppid,args | grep #{parent_pid} | grep -iv grep`

  # break out column output into pid, parent_id, command
  matches = process_output.scan /^\s*(\d+)\s*(\d+)\s*(.*)$/
  return nil if matches.nil? || matches.empty?

  # check for children
  got_children = false
  matches.each do |match|
    next if match.size != 3
    next if got_children == true
    got_children = true if match[1].to_i == parent_pid
  end
  return nil unless got_children

  # fork process
  pid = Process.fork

  if pid.nil?
    # execute "self"
    exec $0
  else
    # detach child process, kill self
    Process.detach pid
    Process.kill 9, Process.pid
  end

end