You will need to use a large file to test this.
Please try this:
file deleted
and then you can sort with stable sort, without stable sort, and compare two. I found these differences:
stable sort:
10012 10012
10012 20012
10013 10013
10013 20013
10014 10014
10014 20014
10015 10015
10015 20015
non-stable sort:
10012 20012
10012 10012
10013 20013
10013 10013
10014 20014
10014 10014
10015 20015
10015 10015
The non-stable sort result may be different from yours since the behavior is undefined.
Thanks!