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wcrtomb - convert a wide character to a multibyte sequence
size_t wcrtomb(char *s, wchar_t wc, mbstate_t *ps);
The main case for this function is when s is not NULL and wc is not
L’\0’. In this case, the wcrtomb() function converts the wide charac‐
ter wc to its multibyte representation and stores it at the beginning
of the character array pointed to by s. It updates the shift state
*ps, and returns the length of said multibyte representation, that is,
the number of bytes written at s.
A different case is when s is not NULL but wc is L’\0’. In this case
the wcrtomb() function stores at the character array pointed to by s
the shift sequence needed to bring *ps back to the initial state, fol‐
lowed by a ’\0’ byte. It updates the shift state *ps (i.e., brings it
into the initial state), and returns the length of the shift sequence
plus one, that is, the number of bytes written at s.
A third case is when s is NULL. In this case wc is ignored, and the
function effectively returns wcrtomb(buf,L’\0’,ps) where buf is an
internal anonymous buffer.
In all of the above cases, if ps is a NULL pointer, a static anonymous
state only known to the wcrtomb() function is used instead.
The wcrtomb() function returns the number of bytes that have been or
would have been written to the byte array at s. If wc can not be rep‐
resented as a multibyte sequence (according to the current locale),
(size_t)(-1) is returned, and errno set to EILSEQ.
The behavior of wcrtomb() depends on the LC_CTYPE category of the cur‐
Passing NULL as ps is not multi-thread safe.