ROS2

See list of packages:

 ros2 pkg list

See list of <packages, executables>:

 ros2 pkg executables

See list of executables from turtlesim packages:

 ros2 pkg executables turtlesim

Where is turtlesim?

 cd /opt/ros/jazzy/
 code .
 Ctrl+P, turtlesim

See list of topics:

 ros2 topic list
 # See datails
 ros2 topic list -t