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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 orienta-
     tion of stream.  It returns a positive value if stream is  wide-charac-
     ter  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  ori-
     ented--that is, if char I/O is permitted but wide-character I/O is dis-
     allowed.  It returns zero if stream has no  orientation  yet;  in  this
     case  the next I/O operation might change the orientation (to byte ori-
     ented 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 per-
     formed through the fwprintf(3) function with the %c and %s  directives.