snprintf(s, l, "%s/%s-%d-%d-%x", dir, pfx, pid, a_fetch_add(&index, 1), n);
} while (!access(s, F_OK) && try++<MAXTRIES);
if (try>=MAXTRIES) {
snprintf(s, l, "%s/%s-%d-%d-%x", dir, pfx, pid, a_fetch_add(&index, 1), n);
} while (!access(s, F_OK) && try++<MAXTRIES);
if (try>=MAXTRIES) {