How to echo a topic if not using ROS?

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Hi Somehow despite being a ROS user for a couple of years, I never realised gazebo has its own publisher / subscriber system that works separately from ROS! I am guessing this somehow works with plugins, however is there an equivalent of

rostopic list rostopic echo

That can be run from the command line to simply monitor the output from the plugins? Or does this need to be added as a cout statement?

Additionally, are the nodes you ca initialize different from ROS nodes? I have read the tutorials but still feel unclear,

Thank you!