char * strsep(char **, const char *)
The strsep() function locates, in the string referenced by
*sp, the first occurrence of any character in the
string delim (or the terminating '\0' character) and
replaces it with a '\0'. The location of the next character after the delimiter
character (or NULL, if the end of the string was
reached) is stored in *sp. An ``empty'' field, i.e. one
caused by two adjacent delimiter characters, can be detected by comparing the location
referenced by the pointer returned in *sp to
'\0'.