Regular Expression to Detect a Specific Query

Question

Hi, I wonder if you anyone can construct a regular expression that can detect if a person searches for something like "site:cnn.com" or "site:www.globe.com.ph/". I've been having the most difficult time figuring it out. Thanks a lot in advance!

Edit: Sorry forgot to mention my script is in PHP.

Answer 1

What are you matching against? A referer url?

Assuming you're matching against a referer url that looks like this:

http://www.google.com/search?client=safari&rls=en-us&q=whatever+site:foo.com&ie=UTF-8&oe=UTF-8

A regex like this should do the trick:

\bsite(?:\:|%3[aA])(?:(?!(?:%20|\+|&|$)).)+

Notes:

• The colon after 'site' can either be unencoded or it can be percent encoded. Most user agents will leave it unencoded (which I believe is actually contrary to the standard), but this will handle both
• I assumed the site:... url would be right-bounded by the equivalent of a space character, end of field (&) or end of string ($)
• I didn't assume x-www-form-urlencoded encoding (spaces == '+') or spaces encoded with percent encoding (space == %20). This will handle both
• The (?:...) is a non-capturing group. (?!...) is a negative lookahead.

Answer 2

Hi Nick, no it's not for a referrer url. My php script basically spits out information about a domain (e.g. backlinks, pagerank etc) and I need that regex so it will know what the user is searching for. If the user enters something that doesn't match the regex, it does a regular web search instead.

Answer 3

If this is all you are trying to do, I guess I'd take the more simple approach and just do:

$entry = $_REQUEST['q'];
$tokens = split(':', trim($entry));
if (1 < count($tokens) && strtolower($tokens[0]) == 'site')
  $site = $tokens[1];

Answer 4

Ok, for input into an arbitary text field, something as simple as the following will work:

\bsite:(\S+)

where the parentheses will capture whatever site/domain they're trying to search. It won't verify it as valid, but validating urls/domains is complex and there are many easily googlable regexes for doing that, for instance, there's one here.

Answer 5

Thanks for your help Nick and Scott. I'll let you know how it goes :)