int loners(char* folder) {
    printf("removing loners \n");

    mutperson_map = (optimizedPerson *)         mmapr(makepath(folder, "mutual_persons",   "bin"), &person_length);
    mutknows_map = (unsigned int *)   mmapr(makepath(folder, "mutual_knows",    "bin"), &knows_length);
    interests_map = (unsigned short *) mmapr(makepath(folder, "interest", "bin"), &interests_length);

    int interests_counter = 0;
    unsigned long knows_offset, interests_offset;

    unsigned int person_offset, person_new_offset;
    int *offset_tracker = malloc(person_length/sizeof(optimizedPerson) * sizeof(int));

    // Files
    char* noloner_persons_file = makepath(folder, "noloner_persons", "bin");
    char* noloner_knows_file = makepath(folder, "noloner_knows", "bin");
    char* noloner_interests_file = makepath(folder, "noloner_interests", "bin");

    remove(noloner_persons_file);
    remove(noloner_knows_file);
    remove(noloner_interests_file);

    noloner_persons = fopen(noloner_persons_file, "a");
    noloner_knows = fopen(noloner_knows_file, "a");
    noloner_interests = fopen(noloner_interests_file, "a");

    // Filtering friendless people

    // Loop over all persons, keep track of new offsets based on knows_n > 0  in an array
    for (person_offset = person_new_offset = 0; person_offset < person_length/sizeof(optimizedPerson); person_offset++) {
        locperson = &mutperson_map[person_offset];
        if(locperson->knows_n > 0) {
            offset_tracker[person_offset] = person_new_offset;
            person_new_offset++;
        } else {
            offset_tracker[person_offset] = -1;
        }
    }

    // Loop over all persons
    // counters for knows and interests firsts
    for (person_offset = person_new_offset = 0; person_offset < person_length/sizeof(optimizedPerson); person_offset++) {
        locperson = &mutperson_map[person_offset];
        // als in array -1, continue
        if (offset_tracker[person_offset] == -1) {
            continue;
        } else{
            // - for vrienden van die persoon, schrijf de juiste offsets op, adjust teller
            for (knows_offset = locperson->knows_first;
            knows_offset < locperson->knows_first + locperson->knows_n;
            knows_offset++) {
                fwrite(&offset_tracker[mutknows_map[knows_offset]], sizeof(unsigned int), 1, noloner_knows);
            }
            // - for for interests van die persoon, schrijf de juiste first op, adjust teller
            locperson->interests_first = interests_counter;
            for (interests_offset = locperson->interests_first;
                interests_offset < locperson->interests_first + locperson->interest_n;
                interests_offset++) {
                //fwrite(&interests_map[interests_offset], sizeof(unsigned short),1, noloner_interests);
                //interests_counter++;
            }
        }
    }

    // Closing up
    fclose(noloner_persons);
    fclose(noloner_knows);

    return 0;
}