Email Regex is causing infinite loop

Question

Can anybody please have a look at
https://regex101.com/r/ApWCG0/1
and correct the regex so that it doesn't give timeout or doesn't cause infinite loop ?
I have been testing it in nodejs and getting an infinite loop and getting in timeout in Regex testing websites.
I have been searching for it for a while on stackoverflow and other websites but couldn't find it. Sorry, if this thread has a duplicate.

my email regex is [a-zA-Z0-9_\-.]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-.]+

Hope somebody get through this.

Update:
[a-zA-Z0-9_\-.]{2,64}@[a-zA-Z0-9\-]{2,64}\.[a-zA-Z0-9\-.]{2,64}
This is covering most cases. I am just restricting the number of characters.

@garglblarg ok, I am watching that, but could you explain why is that giving timeout or infinite loop ? — Vikas Gautam, Dec 07 '16 at 12:32
@garglblarg I tried [http://emailregex.com/email-extractor-tool/](http://emailregex.com/email-extractor-tool/) website with the same content to extract emails from, but this goes in infinite loop. Any idea what would work in this case ? — Vikas Gautam, Dec 07 '16 at 12:42
in this case i suspect that it's not a wrong regex but invalid input _or_ it's not really an infinite loop but just taking very very long which would look the same, i dunno. — garglblarg, Dec 07 '16 at 12:44
Possible duplicate of [Using a regular expression to validate an email address](http://stackoverflow.com/questions/201323/using-a-regular-expression-to-validate-an-email-address) — Mark van Straten, Dec 07 '16 at 12:52

score 1 · Accepted Answer · answered Dec 07 '16 at 12:52

1

I checked your regular expression and found out that if we pass single word[which has extremely high character length] then regular expression fail to check and give timeout error.

E.g: https://regex101.com/r/sjvQ7Z/1

And when I removed that word from your test string then your expresion is working fine.

E.g: https://regex101.com/r/lszdaL/1

answered Dec 07 '16 at 12:52

vijay

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I agree with you sir. but I don't have any control over the input so came up with this `[a-zA-Z0-9_\-.]{2,64}@[a-zA-Z0-9\-]{2,64}\.[a-zA-Z0-9\-.]{2,64}`. The points you have mentioned are the exact words for the problem. I appreciate that. It helped! – Vikas Gautam Dec 07 '16 at 14:19

score 0 · Answer 2 · edited Sep 24 '17 at 19:34

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You experienced catastrophic backtracking because of the Chat Data dump that contained 943k characters. Just remove it and it'll work fine.

edited Sep 24 '17 at 19:34

Graham

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answered Dec 07 '16 at 13:08

Thomas Ayoub

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Ok, I think, backtracking is the technical definition of the problem. thanks for your input. – Vikas Gautam Dec 07 '16 at 14:27

Email Regex is causing infinite loop

2 Answers2