The ccm select -only_in_stack command
pops the selection set stack, setting the current selection set to
the difference between the popped selection set and the previous selection
set. That is, the new selection set contains objects that were in
the popped selection set but not in the previous selection set. For
example, if the top of the stack contains objects {a,b,c} and the
current selection set contains {b,c,d}, then the current selection
set after the command is {a}.
About this task
ccm select -only_in_stack