mbtowc

       #include <stdlib.h>

       int mbtowc(wchar_t *pwc, const char *s, size_t n);

DESCRIPTION
       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 multi-
       byte 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 char-
       acter, 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 func-
       tion, to the initial state, and returns nonzero  if  the  encoding  has
       nontrivial shift state, or zero if the encoding is stateless.

RETURN VALUE
       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  fail-
       ure.

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

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

       +----------+---------------+----------------+
       |Interface | Attribute     | Value          |
       +----------+---------------+----------------+
       |mbtowc()  | Thread safety | MT-Unsafe race |
       +----------+---------------+----------------+
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, C99.

NOTES
       The  behavior  of mbtowc() depends on the LC_CTYPE category of the cur-
       rent locale.

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