mbtowc(3) — Linux manual page


mbtowc(3)               Library Functions Manual               mbtowc(3)

NAME         top

       mbtowc - convert a multibyte sequence to a wide character

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <stdlib.h>

       int mbtowc(wchar_t *restrict pwc, const char s[restrict .n], size_t n);

DESCRIPTION         top

       The main case for this function is when s is not NULL and pwc is
       not NULL.  In this case, the mbtowc() 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 an internal shift state known only
       to the mbtowc() function.  If s does not point to a null byte
       ('\0'), it returns the number of bytes that were consumed from s,
       otherwise it returns 0.

       If the n bytes starting at s do not contain a complete multibyte
       character, or if they contain an invalid multibyte sequence,
       mbtowc() returns -1.  This can happen even if n >= MB_CUR_MAX, if
       the multibyte string contains redundant shift sequences.

       A different case is when s is not NULL but pwc is NULL.  In this
       case, the mbtowc() 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.  The mbtowc() function resets the shift state, only
       known to this function, to the initial state, and returns nonzero
       if the encoding has nontrivial shift state, or zero if the
       encoding is stateless.

RETURN VALUE         top

       If s is not NULL, the mbtowc() function returns the number of
       consumed bytes starting at s, or 0 if s points to a null byte, or
       -1 upon failure.

       If s is NULL, the mbtowc() function returns nonzero if the
       encoding has nontrivial shift state, or zero if the encoding is

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ Interface                    Attribute     Value          │
       │ mbtowc()                     │ Thread safety │ MT-Unsafe race │

VERSIONS         top

       This function is not multithread safe.  The function mbrtowc(3)
       provides a better interface to the same functionality.

STANDARDS         top

       C11, POSIX.1-2008.

HISTORY         top

       POSIX.1-2001, C99.

NOTES         top

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

SEE ALSO         top

       MB_CUR_MAX(3), mblen(3), mbrtowc(3), mbstowcs(3), wcstombs(3),

COLOPHON         top

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Linux man-pages 6.9.1          2024-06-15                      mbtowc(3)

Pages that refer to this page: btowc(3)MB_CUR_MAX(3)mbstowcs(3)wcstombs(3)wctomb(3)