xs_single
err = xs_single(t, XS_DIRECTORY, path, (void **)&strings, &len);
err = xs_single(t, XS_READ, path, retp, len);
ret = xs_single(t, XS_MKDIR, path, NULL, NULL);
ret = xs_single(t, XS_RM, path, NULL, NULL);
err = xs_single(XBT_NULL, XS_TRANSACTION_START, "", &id_str, &len);
err = xs_single(t, XS_TRANSACTION_END, abortstr, NULL, NULL);