badvpn/ncd/examples/dbus_start.ncd

process main {
    call("dbus_start", {{"--session", "--nopidfile"}}) dbus_start;

    println("Got dbus: ", dbus_start.dbus_address);
    rprintln("Lost dbus");
}

template dbus_start {
    alias("_arg0") dbus_args;

    var("false") retrying;

    backtrack_point() retry_point;
    If (retrying) {
        println("dbus_start: retrying in one second");
        sleep("1000", "0");
    };

    retrying->set("true");

    listfrom({"/usr/bin/dbus-daemon"}, dbus_args, {"--print-address"}) dbus_command;

    sys.start_process(dbus_command, "r") proc;
    If (proc.is_error) {
        println("dbus_start: error starting process");
        retry_point->go();
    };

    var("") dbus_address;
    blocker() finished_blocker;

    process_manager() mgr;
    mgr->start("dbus_start__waiter", {});
    mgr->start("dbus_start__reader", {});

    finished_blocker->use();
}

template dbus_start__waiter {
    alias("_caller.proc") proc;
    alias("_caller.retry_point") retry_point;

    proc->wait();
    println("dbus_start: process terminated");
    retry_point->go();
}

template dbus_start__reader {
    alias("_caller.proc") proc;
    alias("_caller.retry_point") retry_point;
    alias("_caller.dbus_address") dbus_address;
    alias("_caller.finished_blocker") finished_blocker;

    proc->read_pipe() rpipe;
    If (rpipe.is_error) {
        println("dbus_start: read pipe error");
        retry_point->go();
    };

    value("") buffer;

    backtrack_point() read_point;
    rpipe->read() data;

    If (data.not_eof) {
        buffer->append(data);

        explode("\n", buffer, "2") exp;
        value(exp) exp;

        num_greater(exp.length, "1") found;
        If (found) {
            exp->get("0") address;
            dbus_address->set(address);
            finished_blocker->up();
        };

        read_point->go();
    };

    println("dbus_start: read pipe eof");
}