wchar_t *wstrsep(wchar_t **stringp, const wchar_t *delim);
wstrsep locates, in the wide string referenced by *stringp, the first occurrence of any wide character in the wide string delim (or the terminating wide null character) and replaces it with a wide null character. The location of the next character after the delimiter wide character (or NULL, if the end of the string was reached) is stored in *stringp. The original value of *stringp is returned.
An empty field (that is, a wide character in the string delim occurs as the first wide character of *stringp can be detected by comparing the location referenced by the returned pointer to a wide null character.
If *stringp is initially null, wstrsep returns null.
wstrsep is not an ISO C function, but appears in BSD4.4 and Linux.