How to compare two text files

[Terry Polzin]

On Thu, 2010-05-06 at 18:27 +0530, W.H. Kalpa Pathum wrote:
> hi,
> 
> I've got two text files containing email addresses one at a row. The
> number of rows in one file is different from the number of the other
> file. email addresses in one file is already there in the other file
> (there are some more also). What I want to do is extract the list
> which is not in the other file.
> 
> elaboration
> 
> File A has 100 email addresses and file B has 15 email addresses. 15
> email addresses in file B are already there in file A. I want to
> extract the 85 mails (excluding the 15 from file B) from file A.
> 
> Any idea on how to accomplish this?
diff -b file_a file_b