run a node topic

ros2 run my_pkg num_publisher

check running topics

**~$ ros2 topic list** 
		/number
		/parameter_events
		/rosout

record a topic

ros2 bag record <list of topics> -o <bag_name>

ros2 bag record \\number -o num_bag

ctrl + c to stop the recording

replay the bag

ros2 bag play num_bag