ros2 launch arg filepath to contents

asked 2022-04-26 15:50:24 -0500

jlack
78 ●6 ●7 ●14

In a ros2 launch file if I declare a launch argument as, DeclareLaunchArgument('my_file_path') then later on I want to load the contents of that file as a parameter to some node, how can I get the contents of that file to do so from the LanuchConfiguration('my_file_path') object?

answered 2022-04-27 02:48:38 -0500

aprotyas
456 ●5 ●32 ●16

Let's say you've declared a LaunchConfiguration substitution for the file path argument, you would have to resolve the provided (possibly relative) path to an absolute path, after which you can just read the file.

from pathlib import Path

file_path = LaunchConfiguration('file_path')
file_path_arg = DeclareLaunchArgument('file_path')

absolute_file_path = Path(file_path).resolve()
with open(absolute_file_path, mode='r') as file_handle:
    file_contents = file_handle.read()

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For completeness, to then pass the file content as a parameter to some node:

LaunchDescription([
    Node(
        package='pkg',
        executable='exec',
        parameters=[{'file_contents': file_contents}])
])

aprotyas ( 2022-04-27 03:14:01 -0500 )edit

This line doesn't work, absolute_file_path = Path(file_path).resolve(). Throws a type error, TypeError: expected str, bytes or os.PathLike object, not LaunchConfiguration

jlack ( 2022-05-02 14:33:25 -0500 )edit

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