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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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mbrtowc(3) Library Functions Manual mbrtowc(3)
mbrtowc - convert a multibyte sequence to a wide character
Standard C library (libc, -lc)
#include <wchar.h>
size_t mbrtowc(size_t n;
wchar_t *restrict pwc, const char s[restrict n],
size_t n, mbstate_t *restrict ps);
The main case for this function is when s is not NULL and pwc is
not NULL. In this case, the mbrtowc() function inspects at most n
bytes of the multibyte string starting at s, extracts the next
complete multibyte character, converts it to a wide character and
stores it at *pwc. It updates the shift state *ps. If the
converted wide character is not L'\0' (the null wide character),
it returns the number of bytes that were consumed from s. If the
converted wide character is L'\0', it resets the shift state *ps
to the initial state and returns 0.
If the n bytes starting at s do not contain a complete multibyte
character, mbrtowc() returns (size_t) -2. This can happen even if
n >= MB_CUR_MAX, if the multibyte string contains redundant shift
sequences.
If the multibyte string starting at s contains an invalid
multibyte sequence before the next complete character, mbrtowc()
returns (size_t) -1 and sets errno to EILSEQ. In this case, the
effects on *ps are undefined.
A different case is when s is not NULL but pwc is NULL. In this
case, the mbrtowc() function behaves as above, except that it does
not store the converted wide character in memory.
A third case is when s is NULL. In this case, pwc and n are
ignored. If the conversion state represented by *ps denotes an
incomplete multibyte character conversion, the mbrtowc() function
returns (size_t) -1, sets errno to EILSEQ, and leaves *ps in an
undefined state. Otherwise, the mbrtowc() function puts *ps in
the initial state and returns 0.
In all of the above cases, if ps is NULL, a static anonymous state
known only to the mbrtowc() function is used instead. Otherwise,
*ps must be a valid mbstate_t object. An mbstate_t object a can
be initialized to the initial state by zeroing it, for example
using
memset(&a, 0, sizeof(a));
The mbrtowc() function returns the number of bytes parsed from the
multibyte sequence starting at s, if a non-L'\0' wide character
was recognized. It returns 0, if a L'\0' wide character was
recognized. It returns (size_t) -1 and sets errno to EILSEQ, if
an invalid multibyte sequence was encountered. It returns
(size_t) -2 if the consumed n bytes form a valid partial character
sequence; more subsequent data needs to be fed in.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────────────┬───────────────┬────────────────────────────┐
│ Interface │ Attribute │ Value │
├───────────────────┼───────────────┼────────────────────────────┤
│ mbrtowc() │ Thread safety │ MT-Unsafe race:mbrtowc/!ps │
└───────────────────┴───────────────┴────────────────────────────┘
C11, POSIX.1-2008.
POSIX.1-2001, C99.
The behavior of mbrtowc() depends on the LC_CTYPE category of the
current locale.
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
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
[email protected]
Linux man-pages 6.15 2025-06-28 mbrtowc(3)
Pages that refer to this page: btowc(3), mbrlen(3), mbsinit(3), mbsnrtowcs(3), mbsrtowcs(3), mbstate_t(3type), mbtowc(3), wprintf(3)
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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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