fwide - set and determine the orientation of a FILE stream
int fwide(FILE *stream, int mode);
Feature Test Macro Requirements for glibc (see feature_test_macros
_XOPEN_SOURCE >= 500 || _ISOC99_SOURCE
_POSIX_C_SOURCE >= 200112L
is zero, the fwide
() function determines the current
orientation of stream
. It returns a positive value if stream
wide-character oriented, that is, if wide-character I/O is permitted but char
I/O is disallowed. It returns a negative value if stream
oriented—that is, 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 operation).
Once a stream has an orientation, it cannot be changed and persists until the
stream is closed.
is nonzero, the fwide
() function first attempts to set
's orientation (to wide-character oriented if mode
greater than 0, or to byte oriented if mode
is less than 0). It then
returns a value denoting the current orientation, as above.
() function returns the stream's orientation, after possibly
changing it. A positive return value means wide-character oriented. A negative
return value means byte oriented. A return value of zero means undecided.
POSIX.1-2001, POSIX.1-2008, C99.
Wide-character output to a byte oriented stream can be performed through the
(3) function with the %lc
Char oriented output to a wide-character oriented stream can be performed
through the fwprintf
(3) function with the %c