What's the difference between strtok and strtok_r in C?

Question

What\'s the difference between strtok and strtok_r in C and when are we supposed to use which?

Answer 1

strtok is equivalent to (and often defined as):

char *strtok(char *str, const char *delim) {
    static char *save;
    return strtok_r(str, delim, &save);
}

in general, you should use strtok_r directly rather than strtok, unless you need to make your code portable to pre-POSIX-2001 systems that only support strtok