subprocess_node

A simple ROS node to invoke bash commands.

Build:

chmod a+x scripts/*.sh subprocess_node/*.py
cd ../..
colcon build --symlink-install --packages-select subprocess_node

Enabling a script to be run as root without a password

1. sudo chown root:root /path/to/script
2. sudo visudo (safer than echo >>)
3. Append the following lines:

   <username> ALL = (ALL) ALL
   <username> ALL = (root) NOPASSWD: /path/to/script
   

   • <username>: result of echo $USER
   • /path/to/script: a file in /this/checkout/root/scripts/
4. Save and apply
5. sudo /path/to/script ARGS

subprocess_node.py

ros2 run subprocess_node subprocess_node.py --ros-args -p cmd:="CMD_AND_ARGS"

Parameters:

• raw (default: false): if true, CMD_AND_ARGS is run as-is. Otherwise, the command that is run is

  bash -c "{sudo }/your/ros2/workspace/src/subprocess_node/scripts/CMD_AND_ARGS"
  

• sudo (default: false): if true, sets {sudo } above

reset_usb_port.sh

ros2 run subprocess_node subprocess_node.py --ros-args -p sudo:=true -p cmd:="reset_usb_port.sh PORT"

where PORT is of the format {bus}-{port}(.{subport})

1. sudo udevadm info -q path -n /dev/device
   • sudo dmesg | tail or lsusb -t could also be used
2. Look at the last port before device label: e.g. /.../2-3:1.0/video4linux/... → bus 2, port 3, no subport
3. PORT then becomes "2-3"