It is possible to run unix scripts in process scheduler. The basic setup instructions are provided in PeopleSft's Customer Connection as "SOLUTION 715584 - E-PRCS: Basics for Implementing Unix scripts as Processes to run via Process Scheduler", and as "Implementing Unix scripts as Processes with PT 7, 7.5, & 8".
The text below describes how it is currently setup in etest88.
The scritp file name for this example (i.e., KSH) must be all caps and executable in the "$PS_HOME/bin" directory in the Unix server where Process Scheduler is running.