Is there a search engine that support regular expression search? [closed]

Answer 1

There isn't an instant search by regex engine. This is likely due to how pages are indexed. Allowing one to grep the web would take a lot of computational power.

Answer 2

Although you are unlikely to find a site that uses full regular expression search, google does have some ability to do matching. Depending what you're trying to achieve this might be enough.

GoogleGuide appears to be fairly in depth with some of the options available. Perhaps if you give an example of the kind of query you want to search for, we can find a solution?

Answer 3

dayyan is correct, it's reverse indexes which make search engines fast; there's no way to accelerate regex search over a petabyte of content if you only have 100 terabytes of flash disk. Keyword searches, reverse index, no problem.

blekko's web grep (https://blekko.com/ws/+/webgrep) supports regexes, but most of the searches we get for it are for constant strings, usually which are in the HTML, because that's what's interesting: who uses microformats? who uses various javascript libraries? who uses various comment systems? And so forth.

If you sent us a regex, we'd be happy to run it for you.

Running these searches consists of a MapReduce job run over all the html in our crawl. That's why it takes a while (a day or two) to get an answer.

Answer 4

Let me write here an answer from the superuser.com question due to my complete solidarity with the author:

quote from the Ask Metafilter:

The only possible way to make keyword searching efficient over hundreds of terabytes (or whatever their index is up to these days) is to precompute an index of words.

In fact a full regex engine is turing-complete, and you can write arbitrary regexps that will gobble up near infinite amounts of CPU time and memory. For all these reasons it would be technical insanity for them to offer regex searching to the general public.

Update: as it rightfully pointed out, regexp is not Turing Complete. Stay tuned for the more detailed answer:

TBD...

Answer 5

If it NEEDS to be regex, then I think you're screwed. But, if you're just looking for more search power, http://www.googleguide.com/advanced_operators_reference.html