List the differences between two folders on different hosts
You want to know the differences between two folders on different unix servers.
This will list the files that are different, based on their contents.
rsync -rvnc /folder/on/the/local/host someremotehost:/folder/on/the/remote/host | grep -E '^deleting|[^/]$' | sed 1d | sed '$d' | sed '$d'
You can get a diff between two files using the following idea:
ssh someremotehost "cat /folder/on/the/remote/host/stuff/file1.txt" | diff /folder/on/the/local/host/stuff/file1.txt -