mblen - determine number of bytes in next multibyte character

       For an explanation of the terms used in this section, see attributes(7).
       ┌──────────────────────────────────────────────────────────────────────┬───────────────┬────────────────┐
       │ Interface                                                            │ Attribute     │ Value          │
       ├──────────────────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │ mblen()                                                              │ Thread safety │ MT-Unsafe race │
       └──────────────────────────────────────────────────────────────────────┴───────────────┴────────────────┘

       If s is not NULL, the mblen() function inspects at most n bytes of the multibyte string starting at s and
       extracts the next complete multibyte character.  It uses a static anonymous shift state known only to the
       mblen()  function.   If  the multibyte character is not the null wide character, it returns the number of
       bytes that were consumed from s.  If the multibyte character is the null wide character, it returns 0.

       If the n bytes starting at s do not contain a complete multibyte character, mblen() returns -1.  This can
       happen even if n is greater than or equal to 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, mblen() also returns -1.

       If  s  is  NULL, the mblen() function resets the shift state, known to only this function, to the initial
       state, and returns nonzero if the encoding has nontrivial  shift  state,  or  zero  if  the  encoding  is
       stateless.

       POSIX.1-2001, C99.

       Standard C library (libc, -lc)

       mblen - determine number of bytes in next multibyte character

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

       The  mblen()  function returns the number of bytes parsed from the multibyte sequence starting at s, if a
       non-null wide character was recognized.  It returns 0, if a  null  wide  character  was  recognized.   It
       returns -1, if an invalid multibyte sequence was encountered or if it couldn't parse a complete multibyte
       character.

mbrlen(3)

Linux man-pages 6.9.1                              2024-05-02                                           mblen(3)

       C11, POSIX.1-2008.

#include<stdlib.h>intmblen(constchars[.n],size_tn);

       The function mbrlen(3) provides a better interface to the same functionality.