Originally Posted by Matt L

Actually, I didn't even have to use grep. Rather, I had previously spent a few hours to create a nice web interface. Enter text in a field, click a button or two, and a few seconds later the culprit pupped up.

These days, I would be archiving the short-term information in a database. A good database engine can do queries like this very, very quickly. The size of the file is almost immaterial.