rosbag and parameters dump with unique timestamp in filename
Dear all,
my problem is the following:
I want to save a rosbag file and dump at the same time the content of the parameter server on a file.
I want the file and the rosbag to have exactly the same time appendix. This is a similar problem to this but not quite the same because it doesn't involve setting the timestamps into parameter server values.
I couldn't find a way to save the timestamp string into an arg, however the following code kind of works for the parameters:
<launch>
<arg name="time_now" value="`date +'%Y-%m-%d-%H-%M-%S'`" />
<rosparam command="dump" param="/robot_description" file="robot_description_$(arg time_now).yaml" />
<node name="rosbag" pkg="rosbag" type="record"
args="-O robot_$(arg time_now).bag /chatter "/>
</launch>
The output says something like:
running rosparam dump robot_description_`date +'%Y-%m-%d-%H-%M-%S'`.yaml /robot_description
but the filename is correct.
However,
when it comes to the rosbag part, the command is not understood, and in particular it believes +'%Y-%m-%d-%H-%M-%S' is a topic to log instead of the argument of date.
I know I could exploit the automatic appending of the string from rosbag, but there is a tiny chance the two string would be different.
I've tried to execute a fake node with a bash script inside that sets up an environment variable to be captured with $(env ...) but it didn't work out.
I've tried to use python and $(eval ...), but I couldn't get to work because I cant import and use time in the same line.
I understood that param are inaccessible from a launchfile (you can only set them but not get) unless you do dirty tricks with launch-prefix.
Is there another way (please don't tell me the only way is to create a Python script to run the rosbag)?
I haven't really looked into this, but does this have to be started from a
.launchfile? A simple shellscript could do this easily (and shell scripts can be started from.launchfiles as well).you mean, calling the ROS commands (i.e.,
rosparam dump,rosbag, etc.) in a bash script and then calling the bash script from the launchfile? That might work but unfortunately it's a code shared among many people and I'm pretty sure they would not accept such change. Previously the launchfile simply had a fixed name for the yaml files and an appendix for the rosbag node.