How to redirect the output back to the screen after freopen("out.txt", "a", stdout)
Unfortunately, there doesn't seem to be a good way:
http://c-faq.com/stdio/undofreopen.html
The best recommendation is not to use freopen in this circumstance.
I can't think of a way to do this in a cross-platform manner, but on GNU/Linux systems (and maybe other POSIX-compliant ones, too) you can freopen ("/dev/tty", "a", stdout). Is this what you were trying to do?