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 .