Google's link: operator tells you all the links that Google knows about.

No, no, and double no! Typing link:www.yoursite.com into Google's search box often won't even show you any links, let alone all of your links. And when it does show you some, they're usually not the best ones. Don't even bother to use this command because it is useless at best. While there are some helpful tools that can find some backward links, there is no foolproof method for finding out about all the links that point to your site or to your competitors' sites. The good news is, just because you can't find them all doesn't mean they don't exist. Keep making a great site and getting the word out about it, and you'll keep building up your link profile, whether or not you can generate an accurate list of them

Source: http://www.highrankings.com/8-seo-myths