FWIDE(3P)

PROLOG
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.

NAME
fwide — set stream orientation

SYNOPSIS

#include <stdio.h>
#include <wchar.h>

int fwide(FILE *stream, int mode);

DESCRIPTION
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.

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 successful.

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.

RETURN VALUE
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 orientation.

ERRORS
The fwide() function may fail if:

EBADF
    The stream argument is not a valid stream.

The following sections are informative.

EXAMPLES
None.

APPLICATION USAGE
A call to fwide() with mode set to zero can be used to determine the current orientation of a stream.

RATIONALE
None.

FUTURE DIRECTIONS
None.

SEE ALSO
The Base Definitions volume of POSIX.1-2017, <stdio.h>, <wchar.h>

COPYRIGHT
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 http://www.opengroup.org/unix/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 https://www.kernel.org/doc/man-pages/reporting_bugs.html .