一个监控juggernaut进程是否被关闭的ruby代码

cmd =  {
   :start => "nohup npm start juggernaut &",
   :ps    => "ps aux | grep npm"
 }

while true
result = `#{cmd[:ps]}`.split("\n").select { |line| line unless line =~ /grep/ }
if result.size < 1
  puts "restart juggernaut"
  system("#{cmd[:start]}")
else
  puts "ok"
end
sleep 5
end

ruby xxx.rb