Guess what this (bash) one-liner does:
bc <<< `tar -c /tmp/a /tmp/b 2>/dev/null | xxd | \
awk '{print $10}' | tr -d '\n' | \
sed -n 's|^.*[0-9]\{7\}\.[0-9]\{7\}\.[0-9]\{7\}\.000000\
00000\.\(.*\)\.[0-9]\{6\}.*[0-9]\{7\}\.[0-9]\{7\}\.[0-9]\{7\}\.000000\
00000\.\([0-9]\{11\}\)\.[0-9]\{6\}.*$|\1 - \2|p' `
In my case it just printed -5… ;o)