There is no direct way to make a system call to execute something from TrafficScript equivalent to system() or exec functions in other languages..
There are some ways in which functionality like this can be emulated but with a few caveats:
1) "Non blocking ONE-WAY" execution (ie: one where the output of the executed event cannot be processes) in a "fire and forget" fashion. This is useful for a custom alert program that something happened.
Using the TrafficScript function event.emit() you can trigger a customised event that can then have an action associated with it under system > alerting to trigger an executable script uploaded to the STM "Extra Files" section (under Catalogs > Extrafiles)
2) "A Blocking Interactive" execution (ie: one where the output of the executed event can be processed). This is useful if the output of the execution needs to be processed:
Using the http.request.*() TrafficScript functions, an interactive http request can be issued to a remote HTTP server that executes the needed code (maybe as a GCI-BIN for example) and returns the appropriate data/value that the TrafficScript can then parse appropriately. Be aware that the http.request.*() functions cannot be used in completion rules.
Using the java.run() TrafficScript function to execute a custom Java Applet on the STM. Be aware that java.run() can only be used with TCP-based protocols and cannot be used in completion rules.