mbrtowc(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

MBRTOWC(3)              Linux Programmer's Manual             MBRTOWC(3)

NAME         top

       mbrtowc - convert a multibyte sequence to a wide character

SYNOPSIS         top

       #include <wchar.h>

       size_t mbrtowc(wchar_t *restrict pwc, const char *restrict s, size_t n,
                      mbstate_t *restrict ps);

DESCRIPTION         top

       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));

RETURN VALUE         top

       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.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).

       ┌───────────────────┬───────────────┬────────────────────────────┐
       │Interface          Attribute     Value                      │
       ├───────────────────┼───────────────┼────────────────────────────┤
       │mbrtowc()          │ Thread safety │ MT-Unsafe race:mbrtowc/!ps │
       └───────────────────┴───────────────┴────────────────────────────┘

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008, C99.

NOTES         top

       The behavior of mbrtowc() depends on the LC_CTYPE category of the
       current locale.

SEE ALSO         top

       mbsinit(3), mbsrtowcs(3)

COLOPHON         top

       This page is part of release 5.13 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                            2021-03-22                     MBRTOWC(3)

Pages that refer to this page: btowc(3)mbrlen(3)mbsinit(3)mbsnrtowcs(3)mbsrtowcs(3)mbtowc(3)wprintf(3)