In this case we can use the sort/comm commands to provide a list of elements
which contains only elements which exist in both lists.
1) The comm command compares two sorted lists and has arguments to control
comm [options] filea fileb
The option -1 will suppress lines only in filea
The option -2 will suppress lines only in fileb
The option -3 will suppress that appear in both filea and fileb
2) The sort command sorts lines of text files.
So we can use the above commands to provide an intersection of the two lists.
nhListElements -noDbDataFor 1 | sort > sortnodb.txt
nhListElements -inGroup SysGroup | sort > sortsysgroup.txt
comm -12 sortnodb.txt sortsysgroup.txt > intersection.txt
The intersection.txt file will contain a list of elements which
appear in both sortnodb.txt and sortsysgroup.txt.