Manual Pages  — LIBXO

The name parameter give the name of the attribute to be encoded. The fmt parameter gives a printf-style format string used to format the value of the attribute using any remaining arguments, or the vap parameter as passed to xo_attr_hv().

    EXAMPLE:
      xo_attr("seconds", "%ld", (unsigned long) login_time);
      struct tm *tmp = localtime(login_time);
      strftime(buf, sizeof(buf), "%R", tmp);
      xo_emit("Logged in at {:login-time} , buf);
    XML:
        <login-time seconds="1408336270">00:14</login-time>

Since attributes are only emitted in XML, their use should be limited to meta-data and additional or redundant representations of data already emitted in other form.