cheat_sheet.md

+Cheat sheet
+===========
+
+The main command line tool is `ros2`, you can use `ros2 -h` to list all the available commands and `ros2 command -h` to get the documentation of any command.
+
+Package
+-------
+
+To create new packages (`[--dependencies list of dependencies]` is optional), for Python:
+
+`ros2 pkg create --build-type ament_python --node-name node_name package_name [--dependencies list of dependencies]`
+
+For C++:
+
+`ros2 pkg create --build-type ament_cmake --node-name node_name package_name [--dependencies list of dependencies]`
+
+Topics
+------
+
+The main command for topics is `ros2 topic`, it can be used to list topics, get information about topics (such as their types)... An other important command is `ros2 interfaces` it can be used to get information about a topic type.
+
+The main tutorials are [Python](https://docs.ros.org/en/foxy/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Py-Publisher-And-Subscriber.html) and [C++](https://docs.ros.org/en/foxy/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Cpp-Publisher-And-Subscriber.html).
+
+In Python, to create a publisher to a topic and publish to it:
+
+```python
+from package_name.msg import TypeOfTopic
+pub = ros_node.create_publisher(TypeOfTopic, 'name_of_topic', 10)
+msg = TypeOfTopic()
+pub.publish(msg)
+```
+
+And to subscribe to a topic:
+
+```python
+from package_name.msg import TypeOfTopic
+sub = ros_node.create_subscription(TypeOfTopic, 'name_of_topic', callback, 10)
+def callback(msg):
+  ros_node.get_logger().info('I heard: "%s"' % msg)
+```
+
+
+Services
+--------
+
+The main command for services is `ros2 service`, it can be used to list services, get information about services (such as their types)... An other important command is `ros2 interfaces` it can be used to get information about a service type.
+
+The main tutorials are [Python](https://docs.ros.org/en/foxy/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Py-Publisher-And-Subscriber.html) and [C++](https://docs.ros.org/en/foxy/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Cpp-Publisher-And-Subscriber.html).
+
+In Python, to create a client to a service and call it:
+
+```python
+from package_name.srv import TypeOfService
+client = ros_node.create_client(TypeOfService, 'name_of_service')
+while not client.wait_for_service(timeout_sec=1.0):
+            ros_node.get_logger().info('service not available, waiting again...')
+req = TypeOfServic.Request()
+future = client.call_async(req)
+rclpy.spin_until_future_complete(ros_node, future) or executor.spin_until_future_complete(future)
+ros_node.get_logger().info('Got '%s' % (future.result()))
+
+```
+
+And to create a server:
+
+```python
+from package_name.srv import TypeOfService
+server = ros_node.create_service(TypeOfService, 'name_of_service', callback)
+def callback(request, response):
+  ros_node.get_logger().info('I heard: "%s"' % request)
+  return response
+```
+
+Actions
+-------
+
+The main command for actions is `ros2 action`, it can be used to list actions, get information about actions (such as their types)... An other important command is `ros2 interfaces` it can be used to get information about an action type.
+