I have two email lists. One is a newline delimited file of just email addresses containing 100k lines and the second file contains email,date,ipaddress newline. It has 4M lines, and contains duplicates which I am not concerned with.
grep -f fileA.txt fileB.txt works when fileA.txt is a test file of 100 or 1000 lines but 100k it is isn't getting anywhere.
I'm open to perl as well :)