Additional tools to handle actions

Since actions are part of the core ROS 2 functionalities, they also get their own command-line tool: ros2 action.

In this section, we’ll learn how to introspect actions, send a goal from the Terminal, and change an action name at runtime.

To see all the possible commands, type ros2 action -h.

Listing and introspecting actions

Actions are based on topics and services. Since rqt_graph doesn’t support services (for now), we could see the topics for an action server and client, but that’s about it. Thus, rqt_graph won’t be very useful for introspecting actions. Because of this, we will use the ros2 command-line tool here.

Let’s learn how to find existing actions and how to get the interface for one action.

Stop all nodes and start the count_until_server node (Python or C++ one). Then, list all available actions by running the following command:

$ ros2 action list
/count_until

Here, we found the...