This script was originally developed so that device specific commands could be issued which were dependent on certain parts of the ip address of the device connected to.
For example, in the Device.CLI.Send Commands activity you could enter the below command;
interface multilink %ctRunExternalScript("C:\ProgramFiles\CatTools3\UserScripts\GetThirdHostnameElement.txt")
And assuming the device ip is aa.bb.cc.dd, the resulting command sent to the device would be;
interface mutilink cc
The script itself is very simple and could easily be modified to return different elements of the ip address.
Please note that running external scripts is currently supported in the follwoing devices only;
Aruba.ArubaOS.General
Cisco.Router.General
Cisco.Switch.IOS
For more information on running external scripts in CatTools see the link below;
http://www.kiwisyslog.com/help/cattools/act_devclisendcmd_runextscrpt.htm