save position of robot online slam?

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Hi

I want to save the current position of robot while the navigation with online slam is running and then i can set those saved position as 2d goals in navigation with static map!

i can get current position of the robot in map frame when i am running navigation stack with static map by subscribing to amcl/pose topic. but in navigation with online slam amcl does not publishes any point. So how can i get robots current position in online slam?

thanks!