Originální popis anglicky:
wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted wide
character output conversion
Návod, kniha: Linux Programmer's Manual
#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);
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.
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.
ISO/ANSI C, UNIX98
fprintf(3),
fputwc(3),
fwide(3),
printf(3),
snprintf(3),
wscanf(3)
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).
