How to notify that a bag file has been completely played? [closed]

edit

Hello everyone.
I built a bag file that, every time is played, sends messaged to two topics. I start bag playing from keyboard:

rosbag play -r 2 subset.bag

On the other side, there's a simple program receiving messages from both topics and calling right functions in a specified class to manage them according to their nature:

int main(int argc, char **argv){
    stage_listener sl;
    char buffer [1024];
    while(1){
        int i = fscanf(stdin,"%s",buffer);

        if(strcmp("exit",buffer) == 0)
            exit(0);

        else if(strcmp("num_nodes",buffer) == 0){
            printf("\nOdometry nodes: %i\nScan nodes: %i\n",sl.numOdom(),sl.numScan());
            //int b = (*sl).numOdom();
        }

        else if(strcmp("listen",buffer) == 0){
            ROS_INFO("Activating topics listening...\n");
            ros::init(argc,argv, "listener");
            ros::NodeHandle n_odom, n_scan;
            ros::Subscriber sub_odom = n_odom.subscribe("/odom", 1000, &stage_listener::addOdomNode, &sl);
            ros::Subscriber sub_scan = n_scan.subscribe("/base_scan", 1000, &stage_listener::addScanNode, &sl); 

            ros::spin();
            ROS_INFO("Listening activity completed");
        }

        else{
            ROS_INFO("Command not found\n");
        }
    }

}

The receiver stands waiting for messages after executing instruction

ros::spin();

The problem is that receiver doesn't know when all messages have been sent and keeps waiting, without regaining control and proceeding in executing subsequent instructions. I want, after the end of messages in bag file, main() function to regain control and print on screen by instruction

ROS_INFO("Listening activity completed");

Then, a new execution of while(1) must start, in such a way new commands can be inserted from keyboard through instruction

int i = fscanf(stdin,"%s",buffer);

Is there a way to break ros::spin() loop when there are no more messages to be received?

Thanks for help.