If you call a shell job at the JobScheduler Agent then you can write the PID in the shell script to stdout so that you see the PID in the task log.
On a linux shell you can use "echo $$".
For Windows look for example here.
Another way is that you look into the task log.
There you see the temporary file which is called on the JobScheduler Agent (e.g. for Linux Agent: SCHEDULER-987 Starting process: '/bin/sh' '-c' '"/tmp/sos.C5NpSU"').
In the ./logs/scheduler.log of the JobScheduler Agent you find
on Linux Agent
\{scheduler\} fork(), execvp("/tmp/sos.C5NpSU")
\{scheduler\} pid=4711
on Windows Agent
..CreateProcess("",""C:\TEMP\sos41CE7.cmd"")
..pid=4711