So, here's that implementation: static char *p; if (!s && !(s = p)) return NULL; s += strspn(s, sep); if (!*s) return p = 0; p = s + strcsp

So, here's that implementation: static char *p; if (!s && !(s = p)) return NULL; s += strspn(s, sep); if (!*s) return p = 0; p = s + strcspn(s, sep); if (*p) *p++ = 0; else p = 0; return s; Instead of carrying that code, or something similar, with my source code or my own utility library I'd much rather have the already debugged version from the standard library. Overwriting the input in C is more efficient than maintaining more internal state and returning a pointer and the length of each token which you would need to strncpy() to get the token into a C string. strtok() does not want to do the initial strdup() for you because only you will know whether your input can already be mutated or whether you need to use a copy. As I pointed in the other reply, strtok() does not break on strings like "keyword=value1,, , value3" unless you skipped RTFM and expect it to do something completely different. And more often than not that's exactly what you want when parsing non-computer readable input which you can expect to take a specific form. If you want to handle escape sequences, parse from a stream (without having the option to fgets() the next line into memory), or parse CSV tables without collapsin colunms then you will want to use something more specific to that. Luckily, strtok() was not advertised as a Swiss army knife so it's off the hook for specific parsing purposes like those.