https://medium.com/@paulyang_38122/%E7%82%BA%E4%BB%80%E9%BA%BC-c-%E8%AA%9E%E8%A8%80%E4%B8%AD%E7%9A%84-printf-%E6%9C%83%E5%A4%9A%E9%82%A3%E5%80%8B%E8%A8%8E%E4%BA%BA%E5%8E%AD%E7%9A%84-f-a77eec6a3b36
