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.
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.1‐2008 defers to the ISO C standard.
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 stream.
If the orientation of the stream has already been determined, fwide()
shall not change it.
The fwide() function shall not change the setting of errno if
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
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 FWIDE(3P)