ivogeorg / launch_tests_pkg

Robotics Masterclass 2024 :: Intermediate/advanced ROS2, Chapters 9-10 - Launch files :: Checkpoint 9

launch_tests_pkg

Notes

1. Parameters vs arguments

This node definition has both:

    rviz_node = Node(
        package='rviz2',
        executable='rviz2',
        output='screen',
        name='rviz_node',
        parameters=[{'use_sim_time': True}],
        arguments=['-d', rviz_config_dir])

use_sim_time is a parameter that every node has and is automatically generated.
-d is the argument for the directory to the rviz2 config file. This is provided on the command line.

2. launch vs run

1. launch requires a launch file (Python, XML, or YAML) which is usually under /launch directory

ros2 launch <pkg_name> <launch_file_name> arg1=:some_value1 arg2=:some_value2

or

ros2 launch <path_to_launch_file> arg1=:some_value1 arg2=:some_value2

2. run requires an executable which is usually under a /lib directory

ros2 run <pkg_name> <executable_name> --ros-args arg1=:some_value1 arg2=:some_value2

3 versions of launch

Robot closeup	Robot LIDAR

Language	Main	Rviz2	Move robot	Exe source
Python	python_main.launch.py	start_rviz_with_arguments.launcy.py	move_with_arguments.launch.py	move_robot_with_arguments.cpp
XML	xml_main.launch.py	start_rviz_with_arguments.launcy.py	move_with_arguments.launch.xml	move_robot_with_params.cpp
YAML	yaml_main.launch.yaml	start_rviz_with_arguments.launcy.py	move_with_arguments.launch.yaml	move_robot_with_params.cpp