size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream);

Writes data from the array pointed to by ptr to the given stream. It writes nmemb number of elements of size size. The total number of bytes written is (size*nmemb).

On success the number of elements writen is returned. On error the total number of elements successfully writen (which may be zero) is returned.