Clearing lines form a text file

I'm currently writing a program which writes some test to a text file, at the moment, everytime it'd run it just appends the output to the previous output. Insead of doing this I need to clear the old output, and replace it with my own.

How could I go about clearing the contents of the text file?

use a different openmode. "w" would clear the file.
Kurt

The term for the behaviour you're looking for is "truncuate". It sounds like you're currently using an append mode like "a". Try "w" as suggested.

http://www.cppreference.com/stdio/fopen.html