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       fwide - set and determine the orientation of a FILE stream


       #include <wchar.h>

       int fwide(FILE *stream, int mode);

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

           _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE ||
           _POSIX_C_SOURCE >= 200112L


       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

       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.


       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.


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


       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.


       fprintf(3), fwprintf(3)


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