wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted
wide-character output conversion
Standard C library (
libc,
-lc)
#include <stdio.h>
#include <wchar.h>
int wprintf(const wchar_t *restrict format, ...);
int fwprintf(FILE *restrict stream,
const wchar_t *restrict format, ...);
int swprintf(wchar_t wcs[restrict .maxlen], size_t maxlen,
const wchar_t *restrict format, ...);
int vwprintf(const wchar_t *restrict format, va_list args);
int vfwprintf(FILE *restrict stream,
const wchar_t *restrict format, va_list args);
int vswprintf(wchar_t wcs[restrict .maxlen], size_t maxlen,
const wchar_t *restrict format, va_list args);
All functions shown above:
_XOPEN_SOURCE >= 500 || _ISOC99_SOURCE
|| _POSIX_C_SOURCE >= 200112L
The
wprintf() family of functions is the wide-character equivalent of the
printf(3) 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
fwide(3) for more information.
The
fwprintf() and
vfwprintf() functions perform wide-character
output to
stream.
stream must not be byte oriented; see
fwide(3) 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(3),
vprintf(3),
fprintf(3),
vfprintf(3),
sprintf(3),
vsprintf(3)
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(3) and vsprintf(3) do not.
(snprintf(3) and vsnprintf(3) 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(3)
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(3) 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 (L'\0'). 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 ('\0'),
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.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
wprintf (), fwprintf (), swprintf (), vwprintf (), vfwprintf (),
vswprintf () |
Thread safety |
MT-Safe locale |
POSIX.1-2001, POSIX.1-2008, C99.
The behavior 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
work correctly only 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 glibc represents wide characters using their
Unicode (ISO-10646) code point, but other platforms don't do this. Also, the
use of 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(3) or
iconv(3), followed by
mbstowcs(3)).
fprintf(3),
fputwc(3),
fwide(3),
printf(3),
snprintf(3)