#include <stdio.h>
#include <wchar.h>
int wprintf(const wchar_t * format , ...);
int fwprintf(FILE * stream , const wchar_t * format , ...); int swprintf(wchar_t * wcs , size_t maxlen , const wchar_t * format , ...);
#include <stdarg.h>
int vwprintf(const wchar_t * format , va_list args ); int vfwprintf(FILE * stream , const wchar_t * format , va_list args ); int vswprintf(wchar_t * wcs , size_t maxlen , const wchar_t * format , va_list args );
DESCRIPTION
The wprintf family of functions is the wide-character equivalent of the printf family of functions. It performs formatted output of wide
characters.
The wprintf and vwprintf functions perform wide character output
to stdout. stdout must not be byte oriented; see function fwide for more information.
The fwprintf and vfwprintf functions perform wide character output
to stream. stream must not be byte oriented; see function fwide for more information.
The swprintf and vswprintf functions perform wide character output
to an array of wide characters.
The programmer must ensure that there is room for at least maxlen wide
characters at wcs.
These functions are like the printf, vprintf, fprintf, vfprintf, sprintf, vsprintf functions except for the
following differences:
The format string is a wide character string.
The output consists of wide characters, not bytes.
swprintf and vswprintf take a maxlen argument, sprintf and vsprintf do not. (snprintf and vsnprintf
take a maxlen argument, but these functions do not return -1 upon
buffer overflow on Linux.)
The treatment of the conversion characters c and s is different:
c
If no l modifier is present, the int argument is converted to a wide character by a call to the btowc function, and the resulting wide character is written.
If an l modifier is present, the wint_t (wide character) argument is written.
s
If no l modifier is present: The "" `` "const char *" '' argument is expected to be a pointer to an array of character type
(pointer to a string) containing a multibyte character sequence beginning
in the initial shift state. Characters from the array are converted to
wide characters (each by a call to the mbrtowc function with a conversion state starting in the initial state before
the first byte). The resulting wide characters are written up to
(but not including) the terminating null wide character. If a precision is
specified, no more wide characters than the number specified are written.
Note that the precision determines the number of wide characters written, not the number of bytes or "screen positions" . The array must contain a terminating null byte, unless a precision is given
and it is so small that the number of converted wide characters reaches it
before the end of the array is reached. -- If an l modifier is present: The "" `` "const wchar_t *" '' argument is expected to be a pointer to an array of wide characters.
Wide characters from the array are written up to (but not including) a
terminating null wide character. If a precision is specified, no more than
the number specified are written. The array must contain a terminating null
wide character, unless a precision is given and it is smaller than or equal
to the number of wide characters in the array.
RETURN VALUE
The functions return the number of wide characters written, excluding the
terminating null wide character in case of the functions swprintf and vswprintf. They return -1 when an error occurs.
The behaviour of wprintf et al. depends on the LC_CTYPE category of the
current locale.
If the format string contains non-ASCII wide characters, the program
will only work correctly if the LC_CTYPE category of the current locale at
run time is the same as the LC_CTYPE category of the current locale at
compile time. This is because the wchar_t representation is platform and locale dependent. (The GNU libc represents
wide characters using their Unicode (ISO-10646) code point, but other
platforms don't do this. Also, the use of ISO C99 universal character names
of the form \unnnn does not solve this problem.) Therefore, in
internationalized programs, the format string should consist of ASCII
wide characters only, or should be constructed at run time in an
internationalized way (e.g. using gettext or iconv , followed by mbstowcs ).
