The fwide() function shall determine the orientation of the stream
pointed to by stream. If mode is greater than zero, the function
first attempts to make the stream wide-oriented. If mode is less than
zero, the function first attempts to make the stream byte-oriented. Otherwise,
mode is zero and the function does not alter the orientation of the
If the orientation of the stream has already been determined, fwide()
shall not change it.
Since no return value is reserved to indicate an error, an application wishing
to check for error situations should set errno to 0, then call
fwide(), then check errno, and if it is non-zero, assume an
error has occurred.
The fwide() function shall return a value greater than zero if, after the
call, the stream has wide-orientation, a value less than zero if the stream
has byte-orientation, or zero if the stream has no orientation.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html