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 buf-
fer 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 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 con-
verted 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 writ-
ten up to (but not including) the terminating null wide charac-
ter (L'\0'). If a precision is specified, no more wide charac-
ters than the number specified are written. Note that the pre-
cision 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 ter-
minating 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 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 at-
tributes(7).
┌─────────────────────────────────────┬───────────────┬────────────────┐
│Interface │ Attribute │ Value │
├─────────────────────────────────────┼───────────────┼────────────────┤
│wprintf(), fwprintf(), swprintf(), │ Thread safety │ MT-Safe locale │
│vwprintf(), vfwprintf(), vswprintf() │ │ │
└─────────────────────────────────────┴───────────────┴────────────────┘
STANDARDS
POSIX.1-2001, POSIX.1-2008, 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 us-
ing 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 on-
ly, or should be constructed at run time in an internationalized way
(e.g., using gettext(3) or iconv(3), followed by mbstowcs(3)).
SEE ALSO
fprintf(3), fputwc(3), fwide(3), printf(3), snprintf(3)
Linux man-pages 6.03 2023-02-05 wprintf(3)
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