16、 Launch file label of ROS (II)

1、launch Document labels

1.param

• It is mainly used to set parameters on the parameter server , It can be loaded through external files
• attribute ：
  • name=“ Namespace / Parameter name ”
    • Parameter name , Can contain namespaces
  • value=“xxx”（ Optional ）
    • Define parameter values , If omitted here , You must specify an external file as the parameter source
  • type=“str/int/double/bool/yaml”( Optional )
    • If the parameter type is not specified , The system will try to determine the parameter type , The following rules ：
      • contain . Numbers ： Think of it as floating point
      • It doesn't contain . The number of ： Think it's an integer
      • Others are strings
• Code implementation ： There are two formats

  <launch deprecated = " Disclaimer ">
      <!--  Disclaimer , Warnings will be given during operation  -->
      <!--  Format 1：launch Next ,node Outside  -->
      <param name="param_A" type="int" value="100" />
      <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" >
          <remap from="/turtle1/cmd_vel" to="/cmd_vel" />
      <!--  Format 2：node Inside , The user-defined node name will be added before the parameter  -->
          <param name="param_B" type="double" value="1.2" />
      </node>
      <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
  </launch>
  

• Running results ：

  /myturtle/param_B
  /param_A
  

2.rosparam

• effect ： from yaml Import... Into the file , export , Delete parameters
• attribute ：
  • command=“load/dump/delete”（ The default is load）
  • file=“$(find xxxx)/xxxx/xxxx…”
    • File load export path
  • param=“ Parameter name ”( Optional ), Used to determine the parameters under that node
  • ns=“ Namespace ”（ Optional ）
• Implementation steps ：
  • 1. Write parameter file yaml

    R: 200
    G: 300
    B: 400
    

  • 2. load: Import parameters
    • Code implementation :( Two formats )

      <launch deprecated = " Disclaimer ">
          <!--  Disclaimer , Warnings will be given during operation  -->
          <!--  Load parameters  -->
          <!--  Format 1： stay node External loading  -->
          <rosparam command="load" file="$(find launch_test_01)/launch/params.yaml" />
          <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" >
              <!--  Format 2： stay node Internal loading , There will be one more node name defined by yourself  -->
              <rosparam command="load" file="$(find launch_test_01)/launch/params.yaml" />
          </node>
          <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
      </launch>
      

    • Running results ：

      PARAMETERS
      * /B: 400
      * /G: 300
      * /R: 200
      * /myturtle/B: 400
      * /myturtle/G: 300
      * /myturtle/R: 200
      

  • 3. dump: Export parameters
    • Code implementation ：
      turtle_start.launch( The node and the export command are in the same file )

      <launch deprecated = " Disclaimer ">
          <!--  Disclaimer , Warnings will be given during operation  -->
          <!--  Load parameters  -->
          <!--  Format 1： stay node External loading  -->
          <rosparam command="load" file="$(find launch_test_01)/launch/params.yaml" />
          <!--  Format 1： stay node Export , All parameters will be exported , But sometimes some parameters will be exported , You'd better write one by yourself launch file , Export parameters  -->
          <!--  Specifies the namespace , Only the parameters in the renamed space will be exported  -->
          <rosparam command="dump" file="$(find launch_test_01)/launch/params_out1.yaml" ns="myturtle" />
          <rosparam command="dump" file="$(find launch_test_01)/launch/params_out2.yaml" />
          <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" >
              <!--  Format 2： stay node Internal loading , There will be one more node name defined by yourself  -->
              <rosparam command="load" file="$(find launch_test_01)/launch/params.yaml" />
              <!--  Format 2： stay node Internal export , Only the parameters under the current node will be exported  -->
              <rosparam command="dump" file="$(find launch_test_01)/launch/params_out3.yaml" />
          </node>
          <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
      </launch>      ```xml
      <launch deprecated = " Disclaimer ">
          <!--  Disclaimer , Warnings will be given during operation  -->
          <!--  Load parameters  -->
          <!--  Format 1： stay node External loading  -->
          <rosparam command="load" file="$(find launch_test_01)/launch/params.yaml" />
          <!--  Format 1： stay node Export , All parameters will be exported , But sometimes some parameters will be exported , You'd better write one by yourself launch file , Export parameters  -->
          <!--  Specifies the namespace , Only the parameters in the renamed space will be exported  -->
          <rosparam command="dump" file="$(find launch_test_01)/launch/params_out1.yaml" ns="myturtle" />
          <rosparam command="dump" file="$(find launch_test_01)/launch/params_out2.yaml" />
          <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" >
              <!--  Format 2： stay node Internal loading , There will be one more node name defined by yourself  -->
              <rosparam command="load" file="$(find launch_test_01)/launch/params.yaml" />
              <!--  Format 2： stay node Internal export , Only the parameters under the current node will be exported  -->
              <rosparam command="dump" file="$(find launch_test_01)/launch/params_out3.yaml" />
          </node>
          <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
      </launch>
      

      params.launch( The node and the export command are not in the same file )

      <launch>
          <!--  Write a single launch file , Prevent incomplete parameter Export  -->
          <rosparam command="dump" file="$(find launch_test_01)/launch/params_out4.yaml" />
      </launch>
      

    • Running results ：
      params_out1.yaml

      B: 400
      G: 300
      R: 200
      background_b: 255
      background_g: 86
      background_r: 69
      param_B: 1.2
      

      params_out2.yaml

      B: 400
      G: 300
      R: 200
      myturtle:
        B: 400
        G: 300
        R: 200
        background_b: 255
        background_g: 86
        background_r: 69
        param_B: 1.2
      param_A: 100
      rosdistro: 'noetic
      
        '
      roslaunch:
        uris:
          host_d102_w65kj1_kk1__33231: http://d102-W65KJ1-KK1:33231/
          host_d102_w65kj1_kk1__33309: http://d102-W65KJ1-KK1:33309/
          host_d102_w65kj1_kk1__33799: http://d102-W65KJ1-KK1:33799/
          host_d102_w65kj1_kk1__43485: http://d102-W65KJ1-KK1:43485/
          host_d102_w65kj1_kk1__44799: http://d102-W65KJ1-KK1:44799/
          host_d102_w65kj1_kk1__45711: http://d102-W65KJ1-KK1:45711/
          host_d102_w65kj1_kk1__46191: http://d102-W65KJ1-KK1:46191/
      rosversion: '1.15.14
      
        '
      run_id: 0f399634-f437-11ec-a9f9-9bef9f37954f
      

      params_out3.yaml

      B: 400
      G: 300
      R: 200
      background_b: 255
      background_g: 86
      background_r: 69
      param_B: 1.2
      

      params_out4.yaml

      B: 400
      G: 300
      R: 200
      myturtle:
        B: 400
        G: 300
        R: 200
        background_b: 255
        background_g: 86
        background_r: 69
        param_B: 1.2
      param_A: 100
      rosdistro: 'noetic
      
        '
      roslaunch:
        uris:
          host_d102_w65kj1_kk1__33231: http://d102-W65KJ1-KK1:33231/
          host_d102_w65kj1_kk1__33309: http://d102-W65KJ1-KK1:33309/
          host_d102_w65kj1_kk1__33799: http://d102-W65KJ1-KK1:33799/
          host_d102_w65kj1_kk1__40997: http://d102-W65KJ1-KK1:40997/
          host_d102_w65kj1_kk1__43485: http://d102-W65KJ1-KK1:43485/
          host_d102_w65kj1_kk1__44799: http://d102-W65KJ1-KK1:44799/
          host_d102_w65kj1_kk1__45711: http://d102-W65KJ1-KK1:45711/
          host_d102_w65kj1_kk1__46191: http://d102-W65KJ1-KK1:46191/
      rosversion: '1.15.14
      
        '
      run_id: 0f399634-f437-11ec-a9f9-9bef9f37954f
      

  • delete: Delete parameters
    • Code implementation ：

      <launch>
          <rosparam command="delete" param="/B" />
      </launch>
      

3.group

• effect ： Grouping nodes , Make the node have ns attribute , So you can start the same node , Use namespaces to distinguish
• attribute ：
  • ns=“ The name space ”( Optional )
  • clear_params=“true/false”（ Optional ： Use with caution ）
• Code implementation ：

  <launch>
      <group ns="first" clear_params="true">
          <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" />
          <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
      </group>
      <group ns="second" clear_params="true">
          <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" />
          <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
      </group>
  </launch>
  

• Running results ：

  rosnode list
  
  /first/mykey
  /first/myturtle
  /myturtle
  /rosout
  /second/mykey
  /second/myturtle
  

4.arg

• effect ： For dynamic parameter transfer , Parameter reuse
• attribute ：
  • name=“ Parameter name ”
  • default=“ The default value is ”( Optional )
  • value=“ The number ”( Optional ,default and value Can't exist at the same time )
  • doc=“ Parameter description ”
• Code implementation ：

  <launch>
      <!--  Be careful ,default and value Can't exist at the same time  -->
      <rosparam command="delete" param="/B" />
      <arg name="car_weight" default="2.3" doc="this is a test" />
      <arg name="car_length" value="2.3" doc="this is a test" />
      <param name="weight" value="$(arg car_weight)" />
      <param name="length" value="$(arg car_length)" />
  </launch>
  

• Running results ：

  rosparam list
  /length
  /weight
  

• Command assignment ：

  roslaunch launch_test_01 arg.launch car_weight:=0.8