xs_single
strings = xs_single(t, XS_DIRECTORY, path, &len);
ret = xs_single(t, XS_READ, path, len);
ret = xs_error(xs_single(t, XS_RM, path, NULL));
id_str = xs_single(XBT_NIL, XS_TRANSACTION_START, "", NULL);
return xs_error(xs_single(t, XS_TRANSACTION_END, abort ? "F" : "T",
err = xs_error(xs_single(XBT_NIL, XS_RESET_WATCHES, "", NULL));