Assuming this is posted to the correct forum – if your Unix script creates an entry in inventory for that machine, a query based policy can launch a script or command to take whatever action you want
This is why I said in my initial email 'Assuming this is posted to the correct forum', which apparently it is not. This forum is for CA Client Automation (otherwise knows as ITCM). It is not for Workload Automation.
FYI What you are trying to do would be very easy with ITCM/CA Client Automation.