``$XDG_RUNTIME_DIR/$appname/$version``.

         For FreeBSD/OpenBSD/NetBSD, it would return ``/var/run/user/$(id -u)/$appname/$version`` if
         exists, otherwise ``/tmp/runtime-$(id -u)/$appname/$version``, if``$XDG_RUNTIME_DIR``
         is not set.
        ÚXDG_RUNTIME_DIRr