Section: POSIX Programmer's Manual (3P)
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
--- set stream orientation
int fwide(FILE *stream, int mode);
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here and the
ISO C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO C standard.
function shall determine the orientation of the stream pointed to by
is greater than zero, the function first attempts to make the stream
is less than zero, the function first attempts to make the stream
is zero and the function does not alter the orientation of the stream.
If the orientation of the stream has already been determined,
shall not change it.
function shall not change the setting of
Since no return value is reserved to indicate an error, an
application wishing to check for error situations should set
to 0, then call
and if it is non-zero, assume an error has occurred.
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.
function may fail if:
argument is not a valid stream.
The following sections are informative.
A call to
set to zero can be used to determine the current orientation of a
The Base Definitions volume of POSIX.1-2017,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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
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