file - Partially truncating a stream (fstream or ofstream) in C++

Question

I am trying to partially truncate (or shorten) an existing file, using fstream. I have tried writing an EOF character, but this seems to do nothing.

Any help would be appreciated...

Answer 1

I don't think you can. There are many functions for moving "up and down" the wrapper hierarchy for HANDLE<->int<->FILE *, at least on Windows, but there is no "proper" to extract the FILE * from an iostreams object (if indeed it is even implemented with one).

You may find this question to be of assistance.

Personally I would strongly recommend steering clear of iostreams, they're poorly designed, heavily C++, and nasty to look at. Take a look at Boost's iostreams, or wrap stdio.h if you need to use classes.

The relevant function for stdio is ftruncate().