[systemd-devel] How to add filter for ActiveState property and get to know for which object this property is?

[Tomasz Michalski]

Hi
I am in the middle of implementation monitor for getting states from
services. I have some question to my current implementation.
My current implementation is:

void main()
{
.....
    r = sd_bus_add_match(&bus,
                         NULL,
                         "type='signal',"
                         "sender='org.freedesktop.systemd1',"
                         "interface='org.freedesktop.DBus.Properties',"
                         "member='PropertiesChanged',"
                         "arg0='org.freedesktop.systemd1.Unit'",
                         propertiesChangedHandler,
                         NULL); //user data*/
    if (r < 0)
    {
        fprintf(stderr, "Failed to add match for PropertiesChanged",
strerror(-r));
        goto finish;
    }

    r = sd_bus_call_method(
                     bus,
                     "org.freedesktop.systemd1",
                     "/org/freedesktop/systemd1",
                     "org.freedesktop.systemd1.Manager",
                     "Subscribe",
                     &error,
                     NULL,
                     NULL);
    if (r < 0)
    {
        fprintf(stderr, "Failed to enable subscription: %s\n", strerror(-r));
        //TO DO use also error code
        return r;
    }

...
}

Handler:
int propertiesChangedHandler(sd_bus_message *message, void *userdata,
sd_bus_error *error)
{
    const char *data;
    const char *path;
    int r = 0;

    if(!message)
        printf("Empty message provided\n");

    path = sd_bus_message_get_path(message);
    if (!path)
    {
        printf("Empty message provided\n");
        return 0;
    }

    r = sd_bus_message_read(message, "s", &data); //here problem with
parsing ActiveState,SubState
    if (r < 0)
    {
        fprintf(stderr, "Failed to parse response message: %s\n",
strerror(-r));
        return 0;
    }
}


Question:
How to narrow down filter? In the above examples the handler will be
triggered by any property change. I am only interested in ActiveState,
eventually SubState trigger. Should I add in sd_bus_add_match:
"arg1='ActiveState'",
"arg2='SubState'"
?
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