I use regular expressions a lot, but not quite enough to remember everything they can do every time I need to do it. Every single time I use them, I forget about one of the resources I usually use to look things up, and regret that I never took the time to write them down. Time to fix that.
- http://regexper.com displays your regex as a finite state machine. Invaluable for figuring out how a complicated regex ticks.
- http://regexr.com allows you to enter a piece of text and see how your regex interacts with it.
- The Java Documentation for Pattern seems to still be the best single page for regex syntax. Obviously there are minor differences based on which language you’re using, but most of the time, what you’re looking for is on this page.