fwide - set and determine the orientation of a FILE stream
int fwide (FILE* stream, int mode);
When mode is zero, the fwide function determines the current orientation
of stream. It returns a value > 0 if stream is wide-character oriented,
i.e. if wide character I/O is permitted but char I/O is disallowed.
It returns a value < 0 if stream is byte oriented, i.e. if char
I/O is permitted but wide character I/O is disallowed. It returns zero
if stream has no orientation yet; in this case the next I/O operation
might change the orientation (to byte oriented if it is a char I/O
operation, or to wide-character oriented if it is a wide character I/O
Once a stream has an orientation, it cannot be changed and persists
until the stream is closed.
When mode is non-zero, the fwide function first attempts to set
stream's orientation (to wide-character oriented if mode > 0, or to
byte oriented if mode < 0). It then returns a value denoting the current
orientation, as above.
The fwide function returns the stream's orientation, after possibly
changing it. A return value > 0 means wide-character oriented. A return
value < 0 means byte oriented. A return value zero means undecided.
ISO/ANSI C, UNIX98
Wide-character output to a byte oriented stream can be performed
through the fprintf function with the %lc and %ls directives.
Char oriented output to a wide-character oriented stream can be performed
through the fwprintf function with the %c and %s directives.
GNU 1999-11-17 FWIDE(3)
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