%n
Last weekend I implemented my own printf() function, sans floating point support. And while reading my copy of
Kernighan and Ritchie's ANSI C book to review the
specifications, I learned of the %n operator for the first
time ever. I had never needed it. Anytime I've ever needed to know the size of things being formatted my needs were always either met by just using the return value of the *printf() function I was using, or by sizing up arguments before allocating a buffer for an snprintf() call.
But when I learned of %n, it was a piece of cake to implement. But now I am having a hard time thinking of a good use for this. Does anybody ever use this conversion character on a regular basis? At all?