[YLUG] Subtracting one list from another.

[Gaffer]

Hi Guys,

How can I subtract items from two lists where one list has items that 
are not in the other list in order to get a list of those items ?

Sorry if that sounds confusing !

I have tried   "diff -a g1.txt g2.txt > g3.txt"  but I end up with a 
file that is as big as the sum of the g1 + g2 file sizes and seems to 
have as entries that are not in either file.

cmp just says the first line is different and stops.

I'm obviously doing something wrong..........!!

-- 
Best Regards:
             Derrick.