I gather that there are both printed as well as on-line concordances for Tanac"h where one could enter a word or phrase and a list of matches appears.
Is there such a thing like a Rash"i or other commentary concordance? Sometimes, I vaguely recall Rash"i said something unusual (for example, I once tried to manually locate where Rash"i says "I don't know") but I don't know where he said it. Ideally, I'd like something that can be used to find matches in both Tanac"h as well as Talmud. On-line source would be better than book form (it's faster - usually :)
Is there any such tool around?