Exact Duplicate: Using a regular expression to validate an email address
What are valid email address characters and patterns and how would you write a regular expression which matches it?
- Dare I start listing the duplicates :P ... stackoverflow.com/questions/201323/…Dana– Dana2009-03-04 18:13:54 +00:00Commented Mar 4, 2009 at 18:13
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3 Answers
Here you go:
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4 Comments
Andrew Hare
LOL - that always cracks me up.
Greg Hewgill
This is a sure sign that you've found the wrong solution to the problem.
Chad Birch
"Some people, when confronted with a problem, think 'I know, I’ll use regular expressions.' Now they have two problems." –Jamie Zawinski
Renaud Bompuis
I don't agree that it's the wrong solution to the problem. Email addresses are very complex to validate but what makes a valid address isn't a moving target, so maintenance, while hard, is not such a big issue. Validating email addresses in code would be complex and not as portable between languages
Here is a good place to start:
http://www.regular-expressions.info/email.html
As a side note, this website is probably the best place to start for regular expression help and tutorials.
Comments
The short answer is: it's complicated.
The most complete and accurate regex I've ever encountered for email validation is the one documented here. It is not for the faint of heart; it's complicated enough that it's broken into parts to make it easier for humans to parse (sample code is in Java). But in cases where going all the way with validation is merited, I don't think it gets much better.
Keep in mind that the specification mentions a lot of cases that may not be considered typical for email addresses. You may want to be aware of them and decide whether those cases are important to you.
In any case, I would suggest that you use unit testing to confirm that your expression covers the cases that you feel are important. That way, as you dink around with it, you can be sure that you haven't broken some case that worked before.
