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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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wprintf(3) Library Functions Manual wprintf(3)
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(size_t n;
wchar_t wcs[restrict n], size_t n,
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(size_t n;
wchar_t wcs[restrict n], size_t n,
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
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 n 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 n argument, sprintf(3)
and vsprintf(3) do not. (snprintf(3) and vsnprintf(3) take
a n 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(). On error, -1 is returned,
and errno is set to indicate the error.
See write(2) and putwc(3). In addition, the following error may
occur:
EOVERFLOW
The value to be returned is greater than INT_MAX.
The fwprintf() and wprintf() functions may fail additionally if:
ENOMEM Insufficient storage space is available.
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() │ │ │
└───────────────────────────────┴───────────────┴────────────────┘
C11, POSIX.1-2008.
POSIX.1-2001, 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/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., 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 the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-06-28 wprintf(3)
Pages that refer to this page: fwide(3), printf(3), printf.h(3head)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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