15、 Launch file label of ROS (I)

1、launch File implementation steps

1. New function pack

• Be careful ： Pay attention to joining launch The function package in the file depends on

2. Create... Under the function pack launch Folder

3. stay launch Create under folder launch file

<launch>
    <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" />
    <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
</launch>

• pkg: Function pack
• type: The node name
• name： Self defined names
• output： Output location

4. call launch file

roslaunch  Package name  xxx.launch 

• Be careful ：roslaunch Command execution launch When you file , We will first judge whether it is started roscore, If it starts , Then the startup will not be repeated

2、launch Document labels

1.deprecated

• effect ： Disclaimer , Tell the user that launch The file is out of date , And warn
• Be careful ：launch It's a label , Other labels are launch Child labels of
• Code implementation ：

  <launch deprecated = " Disclaimer ">
  <!--  Disclaimer , Warnings will be given during operation  -->
      <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" />
      <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
  </launch>
  

• Running results ：

  NODES
  /
      mykey (turtlesim/turtle_teleop_key)
      myturtle (turtlesim/turtlesim_node)
  
  WARNING: [/media/d102/EPAN/Desktop/code_study_ubuntu/rosdemo_05/src/launch_test_01/launch/turtle_start.launch] DEPRECATED:  Disclaimer 
  

2.node

• effect ： Is used to specify the ROS node
• Be careful ：roslaunch Commands do not guarantee that the corresponding nodes are started in the declared order , Because the startup of the node is multithreaded
• pkg=“ Package name ”
  The package to which the node belongs
• type=“nodeType”
  Name of the node to start
• name=“nodeName”
  stay ROS The name of the node in the network topology
• args=“xxx xxx xxx”( Optional )
  Pass parameters to node , The parameters are separated by spaces
• machine=“ machine name ”( Optional )
  because ROS Distributed control ,machine Used to distinguish different machines
• respawn=“true|false”( Optional )
  If the node exits , Whether to restart automatically , When it comes to true when , It will restart automatically , Only kill the whole process （crtl+c）, To exit the corresponding node
• respawn_delay=“T”( Optional )
  When respawn Set to true when , So delay T Restart in seconds
• required=“true|false”( Optional )
  Whether the node must , Set up as true, When the node exits , Will kill the whole launch
• clear_params=“true|false”( Optional )
  Before starting , Delete all parameters of the node's private space
• output=“log|screen”( Optional )
  Log sending destination , The default is log
• ns=“xxx”( Optional )
  Start the node in the specified namespace , Avoid duplicate names

  <launch deprecated = " Disclaimer ">
  <!--  Disclaimer , Warnings will be given during operation  -->
      <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" respawn="true" respawn_delay="10" ns="turtle"/>
      <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
  </launch>
  

3.include

• effect ： When completing a function , You may need to start many nodes , Some nodes may be associated , It needs to be started at the same time , At this time , You can quote what has been written launch file , Become functional package reuse
• Code implementation ：

  <launch>
      <include file="$(find launch_test_01)/launch/turtle_start.launch" />
      <!--  Then add the nodes you need  -->
  </launch>
  

  4.remap

  • effect ： Rename the topic name
  • attribute ：
    • from=“xxx”: Original title
    • to=“xxx”： Target topic name
  • Example ： adopt ROS Own keyboard node (/cmd_vel) Replace the keyboard control node of little turtle (/turtle1/cmd_vel) Control the movement of the little turtle
    • 1. Install the keyboard control package

      sudo apt-get install ros-noetic-teleop-twist-keyboard
      

    • 2. Start keyboard control node

      rosrun teleop_twist_keyboard teleop_twist_keyboard.py 
      

    • 3. To write launch file

      <launch deprecated = " Disclaimer ">
      <!--  Disclaimer , Warnings will be given during operation  -->
          <node pkg="turtlesim" type="turtlesim_node" name="myturtle" output="screen" >
              <remap from="/turtle1/cmd_vel" to="/cmd_vel" />
          </node>
          <node pkg="turtlesim" type="turtle_teleop_key" name="mykey" output="screen" />
      </launch>
      

    • 4. start-up launch file
      • Be careful ： After starting , Little turtle's keyboard control node will no longer be available