brief introduction ： In the sixth 、 7、 ... and 、 Custom messages are described in Chapter 8 （Message）、 service （Service）、 action （Action） Implementation process , In addition, the application of parameters is also introduced , During the learning process, we interspersed some command-line operations to debug or verify relevant functions , This section details the command line operations related to these contents , It is verified by the functions that have been realized in the virtual simulation environment .

         news 、 service 、 Action in ROS2 It is uniformly called interface in （interface）, The command line operation of the interface has been introduced in Section 5 , Our custom interface , Can pass ros2 interface list see , Because I unify all interfaces into the same package , So you can also pass ros2 interface package Command to view all created interfaces , Or use ros2 interface show View the interface content .

         besides , service 、 action 、 Parameters and unique operation commands .

1、 Service operation tools ros2 service

1.1 ros2 service list

Command function ： List the services in the domain ,-t Service message types can be listed at the same time

Command format ：ros2 service list <-t>

1.2 ros2 service type

Command function ： Lists the data types of the specified service

Command format ：ros2 service type <service_name>

1.3 ros2 service find

Command function ： Lists the services in the domain that use the specified data type

Command format ：ros2 service find <type_name>

1.4 ros2 service call

Command function ： Request services synchronously from the command line

Command format ：ros2 servie call <service_name> <type_name> <request_data>

Order sample ：$ ros2 service call /change_map_name duckietown_interface/srv/ChangeMap "{map_name: '4way'}"

2、 Action operation tools ros2 action

2.1 ros2 action list

Command function ： List the available actions in the domain ,-t Action message types can be displayed at the same time

Command format ：ros2 action list <-t>

2.2 ros2 action info

Command function ： View specified action Information , You can see the server and client

Command format ：ros2 action info <action_name>

2.3 ros2 action send_goal

Command function ： Simulate the client to initiate action request

Command format ：ros2 action send_goal <action_name> <type_name> <goal_data> <--feedback>

Order sample ：$ ros2 action send_goal /crossing_acton duckietown_interface/action/Crossing "{speed: 0.2, direction: 'right'}" --feedback

notes ：--feedback Specify whether to display feedback topic information

3、 Parameter operation tool ros2 param

3.1 ros2 param list

Command function ： List the parameters available in the domain

Command format ：ros2 param list

3.2 ros2 param get

Command function ： View the current value of the specified parameter

Command format ：ros2 param get <node_name> <param_name>

3.3 ros2 param set

Command function ： Set the value of the specified parameter

Command format ：ros2 param set <node_name> <param_name> <new_value>

3.4 ros2 param delete

Command function ： Delete parameters （ Generally do not use ）

Command format ：ros2 param delete <node_name> <param_name>

3.5 ros2 param describe

Command function ： Displays descriptive information about declared parameters , Add descriptive information when declaring parameters to view

Command format ：ros2 param describe <node_name> <param_name>

3.6 ros2 param dump

Command function ： All current parameter values “ dump ” Save to a file for later use

Command format ：ros2 param dump <node_name> --output-dir < Save the path >

Order sample ：$ ros2 param dump /line_detect_node --output-dir ~/ros2_ws/src/line_detect/line_detect/

Save the parameters to the same directory as the source file , The file name is consistent with the node name , File for yaml Format , After saving, the contents are as follows ：

/line_detect_node:
  ros__parameters:
    color_select: white
    red_h_high: 10
    red_h_low: 156
    red_s_high: 255
    red_s_low: 43
    red_v_high: 255
    red_v_low: 46
    use_sim_time: false
    white_h_high: 180
    white_h_low: 0
    white_s_high: 50
    white_s_low: 0
    white_v_high: 255
    white_v_low: 100
    yellow_h_high: 34
    yellow_h_low: 26
    yellow_s_high: 255
    yellow_s_low: 43
    yellow_v_high: 255
    yellow_v_low: 46

3.7 ros2 param load

Command function ： Load existing parameters into the node

Command format ：ros2 run <package_name><node_name> --ros-args --params-file <file_name>

Order sample ：$ ros2 run line_detect line_detect_node --ros-args --params-file src/line_detect/line_detect/line_detect_node.yaml