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FWIDE(3)                                                                Linux Programmer's Manual                                                               FWIDE(3)

NAME
       fwide - set and determine the orientation of a FILE stream

SYNOPSIS
       #include <wchar.h>

       int fwide(FILE *stream, int mode);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       fwide():
           _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE
               || _POSIX_C_SOURCE >= 200112L

DESCRIPTION
       When mode is zero, the fwide() function determines the current orientation of stream.  It returns a positive value if stream is 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.  It 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 operation).

       Once a stream has an orientation, it cannot be changed and persists until the stream is closed.

       When mode is nonzero, the fwide() 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.

RETURN VALUE
       The  fwide()  function  returns  the stream's orientation, after possibly changing it.  A positive return value means wide-character oriented.  A negative return
       value means byte oriented.  A return value of zero means undecided.

CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, C99.

NOTES
       Wide-character output to a byte oriented stream can be performed through the fprintf(3) function with the %lc and %ls directives.

       Char oriented output to a wide-character oriented stream can be performed through the fwprintf(3) function with the %c and %s directives.

SEE ALSO
       fprintf(3), fwprintf(3)

GNU                                                                            2021-03-22                                                                       FWIDE(3)