[NTLUG:Discuss] Filtering a list with a list

[Chris Cox]

Daniel Hauck wrote:
> I have a process that generates a list of valid email addresses for a
> system.  I would like to be able to filter that list by removing all
> entries that appear in an exclusion list.
> 

grep has a file option for patterns.
grep -v -f filter.txt list.txt
user1 at domain.com
user2 at domain.com
user3 at domain.com
user4 at domain.com

Assuming list.txt has the whole list and
filter.txt has the exclusion list.