Name

fwide — set and determine the orientation of a FILE stream

Synopsis

        #include <wchar.h>
int fwide( FILE *stream,
  int mode);
 
[Note] Note
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)

COLOPHON

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  Copyright (c) Bruno Haible <haibleclisp.cons.org>

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References consulted:
  GNU glibc-2 source code and manual
  Dinkumware C library reference http://www.dinkumware.com/
  OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
  ISO/IEC 9899:1999