Shell Programming and Scripting

Being linux administrator my task is to keep the machines up and running .Everyday i get a report of list of machines that are up and running.
it would be nice if i get list of machines that are shutdown in comparison to yesterdays report.
for example.If there are 5 machines in my environment
Namely A,B,C,D and E respectively.
Yest report (Running Machines)
Machine A
Machine B
Machine C
Todays Report (Running Machines) .
Machine D
Machine A

I would like to see The Difference between above two cases.
For example
Machine B,C should be reported to derive at conclusion that Machine B and C are shutdown .
How would i include this logic in script?

---------- Post updated at 11:35 PM ---------- Previous update was at 11:02 PM ----------

I m working on diff till now i m able to generate this.
How would i avoid listing unnecessary characters like ">" ,"0a1" ,"2,3d2".
Also MachineD is not needed how would i avoid this?

Code:

# diff -s list1 list2
0a1
> MachineD
2,3d2
< MachineB
< MachineC

Code:

 grep -v -f today yesterday | awk '{print $0" is shutdown"}'

Working fine for above code but if one of the file has empty line then above code output nothing.

Do you means there're always say 4 machines and you wanna output the un-boot machine?

In reality there are 200 machines and yes i want to output unboot machines.

Then you can list all your machines' names in "yesterday" and use that code,and machines which are running in "today",i think it'll give you the result.you can read the man page of "grep" to know what "-v" option means.^_^