Running a node (ros2 run)

The most basic way of running a Node is using the ROS2 tool ros2 run.

More information on it can be obtained through

ros2 run -h

which returns the most relevant arguments package_name and executable_name.

usage: ros2 run [-h] [--prefix PREFIX] package_name executable_name ...

Run a package specific executable

positional arguments:
  package_name     Name of the ROS package
  executable_name  Name of the executable
  argv             Pass arbitrary arguments to the executable

options:
  -h, --help       show this help message and exit
  --prefix PREFIX  Prefix command, which should go before the executable. Command must be wrapped in quotes if it contains spaces (e.g. --prefix 'gdb -ex run --args').

Back to our example, with a properly sourced terminal, the example node can be executed with

ros2 run python_package_with_a_node sample_python_node

which will now correctly output

Hi from python_package_with_a_node.

Troubleshooting tips

If ROS2 is unable to find the node, but it is able to find the package, then you can rely on ros2 pkg executables. For instance, you can run as follows.

ros2 pkg executables python_package_with_a_node

The command, at this stage, should output the following.

python_package_with_a_node sample_python_node

This shows that ROS2 has been correctly able to find sample_python_node within python_package_with_a_node. If the command outputs nothing, this means that no nodes were found.