Best way to get number of insertions and deletions from a diff?

I'd like to probe various commits to see how many lines were added or
removed.  For example,

$ git diff --shortstat HEAD HEAD^1
 3 files changed, 5 insertions(+), 5 deletions(-)

That's great but I'd like to do this from a script and parse out those
numbers.  Is there a more plumbing-level way to do this that would be
more robust?  Or, should I just parse this output?

Thanks ~ Pat