You've reinvented one of the most common questions asked here. And you've already implemented one of the most common solutions. So bonus points for that ;-)

Unfortunately, while there are variations, there isn't really a better way of performing this trick. But you could see How do I change one line in a file/delete a line in a file/insert a line in the middle of a file/append to the beginning of a file? for further comments

--
Tommy
Too stupid to live.
Too stubborn to die.