我要学习ros2相关的语法知识，因此利用Google搜索技巧“学习内容+wiki tutorial”,发现ros的official website document，里边有关于ros2的tutorial，以及how to install and question fourm.these source interest me a lot.
ros2 version: humble
参考资料：http://docs.ros.org/en/humble/Tutorials.html
so,now i want to share some note about ros2 grammar.

1. ros2 environment config
2. ros2 run
3. ros2 node
4. ros2 topic
5. ros2 service
6. ros2 action
7. ros2 parameters
8. ros2_gui aqt
9. ros2 interface show
10. ros2 lanuch
11. yaml
    总体来说，语法学习起来还是比较简单的，学习起来也是比较有趣，official tutorial讲解的比较有趣，结合turtlesim_package，实践与理论相结合，很轻松。
    那么接下来我要继续学习client相关的知识，也就是beginner的第二阶段，加油！

some note:

环境配置

1. check ros2 version
2. check ros2 environment value
   1. check ros2 environment shell setup.shz
3. ros2 node
   1. node list
   2. node info
   3. aqt_graph
   4. —ros-args —remap __node:=
4. ros2 topic
   1. topic list
   2. topic list -t
   3. msg type
   4. topic echo
   5. topic interface show:struct of msg type
   6. topic pub [—once/—rate ] “{yaml}”
   7. topic hz
5. ros2 service
   1. service list
   2. service list -t
   3. service type <srv_name>
   4. interface show <srv_type>
   5. service call <srv_name> <srv_type> “{yaml}”
   6. service find <srv_type>
6. ros2 parameters
   1. ros2 param list
   2. ros2 param get <node_name> <param_name>
   3. ros2 param set <node_name> <param_name> value
   4. ros2 param dump <node_name> > <file_name>.yaml
   5. ros2 param load <node_name> <file_name>.yaml
   6. ros2 run turtlesim turtlesim_node —ros-args —params-file <file_name>.yaml
7. ros2 action
   1. ros2 action list
   2. ros2 action list -t
   3. ros2 action info <action_name>
   4. ros2 action send_goal <action_name> <action_type> “{yaml}”
   5. ros2 interface show <action_type_name>
8. yaml
   http://wiki.ros.org/YAML Overview