int wctomb(char *str, wchar_t wchar);

Examines the code which corresponds to a multibyte character given by the argument wchar. The code is converted to a multibyte character and stored into the string pointed to by the argument str if str is not null.

If str is a null pointer, then zero is returned if multibyte characters are not state-dependent (shift state). Otherwise a nonzero value is returned if multibyte character are state-dependent.

If str is not null, then the number of bytes that are contained in the multibyte character wchar are returned. A value of -1 is returned if wchar is not a valid multibyte character.