* Prev: <a href="/content/topics/robotics/ros_book/40_prr_ros_services/">4: Services</a> * Next: <a href="/content/topics/robotics/ros_book/50_prr_actions/">5: Actions</a> ## Example: WordCount.srv * WordCount.srv shows that it will take one input (string) and give one output (uint32) * Notice some hairy tweaks of both CMakeLists.txt and package.xml * Once done run catkin make (`$ cm`) to process and do the code generation * You will immediately be able to see the service declared with `$ rossrv show WordCount` <slide_break></slide_break> ### Defining the logic * It looks a lot like a node subscribing to a topic * Big difference is that it has a 'return' statement * In this example, it returns an integer equal to the number of words * The money quote: `return len(request.words.split())` * Notice the two ways of returning the result * Everything else is plumbing <slide_break></slide_break> ### Implementing a Service * Run the service with a standard `rosrun` command * Remember our package is called `samples` * Remember that you must have `roscore` running! * `rosrun samples service_server.py` * You can tell that it worked: 1. It shows up in `$ rosservice list` 1. It shows up in `$ rosservice info word_count`