mbrtowc - convert a multibyte sequence to a wide character
#include <wchar.h>
size_t mbrtowc(wchar_t *pwc, const char *s, size_t n, mbstate_t *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 it couldn't parse a complete multibyte character, meaning that n
should be increased.
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value |
mbrtowc() | Thread safety | MT-Unsafe race:mbrtowc/!ps |
POSIX.1-2001, POSIX.1-2008, C99.
The behavior of mbrtowc() depends on the LC_CTYPE category of the current locale.
This page is part of release 5.10 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/.