wcrtomb - convert wide characters to multi-byte characters

Syntax	#include <wchar.h> size_t wcrtomb(char *s, wchar_t wc, mbstate_t *ps);
Description	If s is a null pointer, wcrtomb() corresponds to the call wcrtomb(buf, L'\0', ps) where buf designates an internal buffer. If s is not a null pointer, wcrtomb() determines how many bytes are required to represent the multi-byte character corresponding to wc. Any Shift sequences are also taken into account. The resulting bytes are written to the array whose first element is pointed to by s. A maximum of {MB_CUR_MAX} bytes are written. If wc is the null character, a null byte is written that can preceded a Shift sequence that restores the initial conversion state. The final state corresponds to the “initial conversion” state.
Return val.	(size_t)-1	if wc does not represent a valid wide character. The value of the EILSEQ macro is written to errno. The conversion status is undefined.
	the number of bytes written to the array *s
		otherwise
Notes	This version of the C runtime system only supports 1-byte characters as wide character codes.
See also	mblen(), mbtowc(), wcstombs(), wctomb().