Sick_tim Udev

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Hello I'm a beginner in ROS and Linux, please excuse my dump question but....

I successfully installed sick_tim package but the "udev" step i can't execute correctly
I follow the instructions written in the README.txt file inside "udev" folder, but the terminal told me it can't find "81-sick-tim3xx.rules" My command is:

sudo cp sick_tim/udev/81-sick-tim3xx.rules /etc/udev/rules.d

How can i find the package's installation directory? I think "81-sick-tim3xx.rules" is inside the installation directory and i need to write the full path to the file, is it correct or not?