F_DUPUID
if (!(up->u_flags & F_DUPUID) && getpwuid((uid_t)(up->u_uid)) != NULL) {
if (!(up->u_flags & F_DUPUID) && getpwnam(login_name) != NULL) {
if (!(up->u_flags & F_DUPUID) &&
up->u_flags |= F_DUPUID;
up->u_flags |= F_DUPUID;