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WPRINTF(3) Linux Programmer's Manual WPRINTF(3)
wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted wide-
character output conversion
#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, ...);
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);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
All functions shown above:
_XOPEN_SOURCE >= 500 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
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:
o The format string is a wide-character string.
o The output consists of wide characters, not bytes.
o 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. 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.
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 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
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)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2010-09-20 WPRINTF(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface