I want to share a little script I wrote that check if two directory is identical rather efficiently. First you may need to understand what sha1sum does.
The sha1sum tool
As the name may suggest, sha1sum compute the SHA-1 checksum of a particular file / text string.
[jason@madcoda ~]# echo "Hello World" | sha1sum
[jason@madcoda ~]# echo "Hello World" > hello.txt
[jason@madcoda ~]# sha1sum hello.txt
You can see from the above example that sha1sum produce a hash of the content,