Sets the file position indicator for handle to the beginning of the file stream.
Zwraca TRUE w przypadku sukcesu, FALSE w przypadku porażki.
The file pointer must be valid, and must point to a file successfully opened by fopen().
Notatka: If you have opened the file in append ("a" or "a+") mode, any data you write to the file will always be appended, regardless of the file position.