Keyboard input fails to be processed when node is launched by launch.py file

[Curiosi-Orch]

Bug report

Keyboard input fails to be processed when node is launched by launch.py file

• Operating System: Ubuntu 18.04
• Installation type: ROS2 dashing
• Client library (if applicable): rclcpp

Steps to reproduce issue

c++ getchar() function cannot be processed when the rclcpp node is launched in launch.py file, and neither was the case when I launched the turtle_teleop_key node in turtlesim tutorial package in the same way. I am not sure if there should be any modification for the launch.py file. btw, it works well in ROS1.

Expected behavior

program can read the keyboard input correctly.

Actual behavior

no response to the keyboard input.

My code in test.launch.py

def generate_launch_description(): test = Node(package='turtlesim', node_name='turtle_teleop_key', node_executable='turtle_teleop_key', output='screen')
return LaunchDescription([test,])

[clalancette]

c++ getchar() function cannot be processed when the rclcpp node is launched in launch.py file, and neither was the case when I launched the turtle_teleop_key node in turtlesim tutorial package in the same way. I am not sure if there should be any modification for the launch.py file. btw, it works well in ROS1.

In my opinion, this is a feature, not a bug. A launch file is meant to launch many processes; what happens if you have 2 (or more) of them that both want to consume stdin? Which one should get it?

That said, I'll leave this open for a little while to see if anyone has other ideas, or a straightforward way to make this determination (and make it clear to users).

[Curiosi-Orch]

c++ getchar() function cannot be processed when the rclcpp node is launched in launch.py file, and neither was the case when I launched the turtle_teleop_key node in turtlesim tutorial package in the same way. I am not sure if there should be any modification for the launch.py file. btw, it works well in ROS1.

In my opinion, this is a feature, not a bug. A launch file is meant to launch many processes; what happens if you have 2 (or more) of them that both want to consume stdin? Which one should get it?

That said, I'll leave this open for a little while to see if anyone has other ideas, or a straightforward way to make this determination (and make it clear to users).

Thank you for your reply! it makes sense, but also makes some inconvenience. lol

[clalancette]

I'm going to close this one out, as I don't think there is much to do here. If you disagree, feel free to reopen (but I would also say that we would need an idea on how we would possibly fix this to consider it).