How did you manage to double the content without having a print statement? Don't just follow the advice of the people who suggested to use +< in the open. You probably need it, but you need more too. You cannot simply read a line, write a line in a file that you have open for read/write - it will garble your data horribly.

But since your code fragment doesn't show any print statements, I expect your real code is different anyway.

Abigail