I am not an avid user of Clearcase but I recently had to use it in a CRON job. First write your normal script. Then I had to use this approach to get the script to work by setting the clearcase environment first.
This script sets the environment then calls the main scripts.
cleartool setview -exec "/home/k/kcastell/dp-mgt/scripts/SIcertreport.sh" kevin_unix
cleartool setview -exec "/home/k/kcastell/dp-mgt/scripts/Prodcertreport.sh" kevin_unix
The "kevin_unix" is the name of my view in clearcase.
It is all based on the use of "exec" in each line.