Recieve last Message on topic after subscription

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I have around 50 Topics, all of them are activly sent - so this will not work. So ROS does not have a standard way to do this?

you can use timestamp. but still can you write more on what exactly you are trying to do

I start a replay with Rosbag (~50 recorded Topics), I start rviz, I recognize an error so i stop rosbag, then I want to evaluate the Data in rviz - without unpausing rosbag!

Have you tried running rviz from the beginning? All the data should be there when you pause playback.

then the question is: How can i access this data?

What do you mean, all the data should be buffered and displayed in rviz already. Use the standard plugins to view the data. When time pauses, due to the bag stopping playback it will all be right there.

I cannot use the standard plugins for all of my data, so i have written my own. And when I subscribe to a topic, then I want to have the last message on any topic - topics that i was not subscribed to, when this message came.

you can try http://wiki.ros.org/rosbag/Code%20API to access data in rosbag