wprintf(3) Library Functions Manual wprintf(3)
NAME
wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted
wide-character output conversion
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#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);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
All functions shown above:
_XOPEN_SOURCE >= 500 || _ISOC99_SOURCE
|| _POSIX_C_SOURCE >= 200112L
DESCRIPTION
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 infor-
mation.
The fwprintf() and vfwprintf() functions perform wide-character output
to stream. stream must not be byte oriented; see fwide(3) for more in-
formation.
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), vf-
printf(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 over-
flow 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 re-
sulting 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 ex-
pected 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 charac-
ter, 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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌─────────────────────────────────────┬───────────────┬────────────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────────────────┼───────────────┼────────────────┤
│ wprintf(), fwprintf(), swprintf(), │ Thread safety │ MT-Safe locale │
│ vwprintf(), vfwprintf(), │ │ │
│ vswprintf() │ │ │
└─────────────────────────────────────┴───────────────┴────────────────┘
STANDARDS
C11, POSIX.1-2008.
HISTORY
POSIX.1-2001, C99.
NOTES
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 plat-
form- and locale-dependent. (The glibc represents wide characters using
their Unicode (ISO/IEC 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., us-
ing gettext(3) or iconv(3), followed by mbstowcs(3)).
SEE ALSO
fprintf(3), fputwc(3), fwide(3), printf(3), snprintf(3)
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