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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
WPRINTF(3) Linux Programmer's Manual WPRINTF(3)
wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - format‐
ted 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
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(), │ Thread safety │ MT-Safe locale │
│swprintf(), vwprintf(), │ │ │
│vfwprintf(), vswprintf() │ │ │
└─────────────────────────┴───────────────┴────────────────┘
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)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2016-03-15 WPRINTF(3)
Pages that refer to this page: fwide(3), printf(3)