fwide

int fwide(FILE *stream, int mode);

The function determines the orientation of the stream stream. If mode is greater than zero, it first attempts to make the stream wide oriented. If mode is less than zero, it first attempts to make the stream byte oriented. In any event, the function returns:

• A value greater than zero if the stream is left wide-oriented.
• Zero if the stream is left unbound.
• A value less than zero if the stream is left byte-oriented.

In no event will the function alter the orientation of a stream after it has been oriented.