strsep - extract token from string
char *strsep(char **stringp, const char *delim);
The strsep() function returns the next token from the string
stringp which is delimited by delim. The token is terminated
with a `\0' character and stringp is updated to point past the token.
The strsep() function returns a pointer to the token, or NULL if
delim is not found in stringp.
The strsep() function was introduced as a replacement for
strtok(), since the latter cannot handle empty fields. (However,
strtok() conforms to ANSI-C and hence is more portable.)