Shell Programming and Scripting

I am not too understand shell script writing , could someone can help me ,

I want to have a shell script for testing , the process will run repeatly (looping), I want to test the CPU time , I have the below script to test :

while x=0
do
cp /tmp/abc.txt /tmp/def.txt
done

the process is non-stop running , but it is not fit my requirement , because the above script will generate a new process after the old process was completed , what I want is a SAME process is running a non-stop process (same PID ) ,

More clearly , I just want to have a script to run a process ( may be a looping ) , this process need to use the same PID . In my previous script , after the cp process finished , it will generate another process ( so the PID changed ) so not fit my requirement.
could someone can post the script ? thx in advance.

No one can post such a script. Your script is running one process after another each new process will get a new pid.

try this:

#!/bin/ksh

while [ 1 ]
do
cp source.txt dest.txt
sleep 1
done