#include <stdio.h>
  int setvbuf( FILE *stream, char *buffer, int mode, size_t size );

The function setvbuf() sets the buffer for stream to be buffer, with a size of size. mode can be:

• _IOFBF, which indicates full buffering
• _IOLBF, which means line buffering
• _IONBF, which means no buffering