Section: Linux Programmer's Manual (3)
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fwide - set and determine the orientation of a FILE stream
int fwide(FILE *stream, int mode);
Feature Test Macro Requirements for glibc (see
_XOPEN_SOURCE >= 500 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L
is zero, the
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
is byte oriented---that is,
if char I/O is permitted but wide-character I/O is disallowed.
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 nonzero, the
function first attempts to set
stream's orientation (to wide-character oriented
if mode is 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
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
function with the
Char oriented output to a wide-character oriented stream can be performed
function with the
This page is part of release 4.16 of the Linux
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