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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | NOTES | SEE ALSO | COLOPHON |
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mbsnrtowcs(3) Library Functions Manual mbsnrtowcs(3)
mbsnrtowcs - convert a multibyte string to a wide-character string
Standard C library (libc, -lc)
#include <wchar.h>
size_t mbsnrtowcs(size_t size;
wchar_t dest[restrict size], const char **restrict src,
size_t nms, size_t size, mbstate_t *restrict ps);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
mbsnrtowcs():
Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L
Before glibc 2.10:
_GNU_SOURCE
The mbsnrtowcs() function is like the mbsrtowcs(3) function,
except that the number of bytes to be converted, starting at *src,
is limited to at most nms bytes.
If dest is not NULL, the mbsnrtowcs() function converts at most
nms bytes from the multibyte string *src to a wide-character
string starting at dest. At most size wide characters are written
to dest. The shift state *ps is updated. The conversion is
effectively performed by repeatedly calling mbrtowc(dest, *src, n,
ps) where n is some positive number, as long as this call
succeeds, and then incrementing dest by one and *src by the number
of bytes consumed. The conversion can stop for three reasons:
• An invalid multibyte sequence has been encountered. In this
case, *src is left pointing to the invalid multibyte sequence,
(size_t) -1 is returned, and errno is set to EILSEQ.
• The nms limit forces a stop, or size non-L'\0' wide characters
have been stored at dest. In this case, *src is left pointing
to the next multibyte sequence to be converted, and the number
of wide characters written to dest is returned.
• The multibyte string has been completely converted, including
the terminating null wide character ('\0') (which has the side
effect of bringing back *ps to the initial state). In this
case, *src is set to NULL, and the number of wide characters
written to dest, excluding the terminating null wide character,
is returned.
According to POSIX.1, if the input buffer ends with an incomplete
character, it is unspecified whether conversion stops at the end
of the previous character (if any), or at the end of the input
buffer. The glibc implementation adopts the former behavior.
If dest is NULL, size is ignored, and the conversion proceeds as
above, except that the converted wide characters are not written
out to memory, and that no destination size limit exists.
In both of the above cases, if ps is NULL, a static anonymous
state known only to the mbsnrtowcs() function is used instead.
The programmer must ensure that there is room for at least size
wide characters at dest.
The mbsnrtowcs() function returns the number of wide characters
that make up the converted part of the wide-character string, not
including the terminating null wide character. If an invalid
multibyte sequence was encountered, (size_t) -1 is returned, and
errno set to EILSEQ.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────┬───────────────┬─────────────────────────────────┐
│ Interface │ Attribute │ Value │
├──────────────┼───────────────┼─────────────────────────────────┤
│ mbsnrtowcs() │ Thread safety │ MT-Unsafe race:mbsnrtowcs/!ps │
└──────────────┴───────────────┴─────────────────────────────────┘
POSIX.1-2008.
The behavior of mbsnrtowcs() depends on the LC_CTYPE category of
the current locale.
Passing NULL as ps is not multithread safe.
iconv(3), mbrtowc(3), mbsinit(3), mbsrtowcs(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
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⟨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-
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Linux man-pages 6.15 2025-06-28 mbsnrtowcs(3)
Pages that refer to this page: mbsrtowcs(3)
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