315
[xkcd] Regular Expressions (10 Jan 2007)
(programming.dev)
Hover Text:
Wait, forgot to escape a space. Wheeeeee[taptaptap]eeeeee!
Transcript
[in a yellow box:]
Whenever I learn a new skill I concoct elaborate fantasy scenarios where it lets me save the day.Megan: Oh no! The killer must have followed her on vacation!
[Megan points to computer.]
Megan: But to find them we'd have to search through 200 MB of emails looking for something formatted like an address!
Cueball: It's hopeless!Off-panel voice: Everybody stand back.
Off-panel voice: I know regular expressions.
[A man swings in on a rope, toward the computer.]
tap tap
The word PERL! appears in a bubble.[The man swings away, and the other characters cheer.]
You're completely correct. In practice, it's usually good enough to just check for ".+@.+" or ".+@.+\..+". Why? It's broad enough to allow almost everything and it rejects the most obvious typos. And in the end, the final verification would be to send an email there which contains a link, that one has to click to finalize the signup/change. Even if you had a regex that could filter every possible adress that's possible according to the standard, you still wouldn't know whether it really exists.