//// You must free the result if result is non-NULL.
//char *str_replace(char *orig, char *rep, char *with) {
//    char *result; // the return string
//    char *ins;    // the next insert point
//    char *tmp;    // varies
//    int len_rep;  // length of rep (the string to remove)
//    int len_with; // length of with (the string to replace rep with)
//    int len_front; // distance between rep and end of last rep
//    int count;    // number of replacements

//    // sanity checks and initialization
//    if (!orig || !rep)
//        return null;
//    len_rep = len(rep);
//    if (len_rep == 0)
//        return null; // empty rep causes infinite loop during count
//    if (!with)
//        with = "";
//    len_with = len(with);

//    // count the number of replacements needed
//    ins = orig;
//    for (count = 0; tmp = instr(ins, rep); ++count) {
//        ins = tmp + len_rep;
//    }

//    tmp = result = malloc(len(orig) + (len_with - len_rep) * count + 1);

//    if (!result)
//        return null;

//    // first time through the loop, all the variable are set correctly
//    // from here on,
//    //    tmp points to the end of the result string
//    //    ins points to the next occurrence of rep in orig
//    //    orig points to the remainder of orig after "end of rep"
//    while (count--) {
//        ins = instr(orig, rep);
//        len_front = ins - orig;
//        tmp = mid(tmp, orig, len_front) + len_front;
//        tmp = strcpy(tmp, with) + len_with;
//        orig += len_front + len_rep; // move to next "end of rep"
//    }
//    strcpy(tmp, orig);
//    return result;
//}