wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vsw
printf - formatted wide character output conversion
SYNOPSIS
#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 charac
ter output to stream. stream must not be byte oriented;
see function fwide for more information.
The swprintf and vswprintf functions perform wide charac
ter 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 fol
lowing 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 func
tions do not return -1 upon buffer overflow on
Linux.)
The treatment of the conversion characters c and s is dif
ferent:
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 ini
tial 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 charac
ters 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 termi
nating 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 char
acters 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 writ
ten, excluding the terminating null wide character in case
of the functions swprintf and vswprintf. They return -1
when an error occurs.
CONFORMING TO
ISO/ANSI C, UNIX98
SEE ALSO
printf(3), fprintf(3), snprintf(3), fputwc(3), fwide(3),
wscanf(3)
NOTES
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
the LC_CTYPE category of the current locale at compile
time. This is because the wchar_t representation is plat
form 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 pro
grams, 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).
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