2
I can't get this simple regular expression to work for matching emails:
'\w*(?:\.\w*)*@\w*(?:\.\w*)*\w\{2,5\}'
It should be working as I have tested it with regex pal and it works just fine. I think there's a problem with optional character class but I'm not sure.
brgs
Posted 2011-08-03T11:32:32.003
Reputation: 123
2
You should use grep with perl regular expression (-P option) which supports lookahead assertions like (?: ). Also curly braces shouldn't be escaped.
Try:
grep -P '\w*(?:\.\w*)*@\w*(?:\.\w*)*\w{2,5}'
Since perl expressions are experimental feature in GNU grep you may want to change (?: ) to ( ) and user extended expressions (-E):
grep -E '\w*(\.\w*)*@\w*(\.\w*)*\w{2,5}'
Some of the extended expression implementations do not support curly braces { and }. For portability you can use basic regular expressions.
To use basic regular expressions escape ( and ) and leave also { and } escaped.
grep '\w*\(\.\w*\)*@\w*\(\.\w*\)*\w\{2,5\}'
Paweł Nadolski
Posted 2011-08-03T11:32:32.003
Reputation: 966
1What is it intended to do? – Mechanical snail – 2011-08-03T11:34:18.430
To match the email. – brgs – 2011-08-03T11:35:54.327
Then it's wrong. A lot more than
– Mechanical snail – 2011-08-03T11:38:04.933\word characters are permitted in an e-mail address. See http://en.wikipedia.org/wiki/Email_address#Syntax.The actual specification is http://tools.ietf.org/html/rfc5322.
– Mechanical snail – 2011-08-03T11:39:04.917Yeah, I know that, but I'm testing it on a certain email - email.something@blah.mailas.com – brgs – 2011-08-03T11:39:25.867
See http://stackoverflow.com/questions/201323/what-is-the-best-regular-expression-for-validating-email-addresses
– Mechanical snail – 2011-08-03T11:41:29.873Thanks, but I won't be using this expression for anything, only for testing.. I just want to know WHY it doesn't work? Should I use egrep or something? – brgs – 2011-08-03T11:46:19.073
Egrep with expression '\w(.(\w))@\w(.(\w)).\w{2,5}' worked, I guess there's no optional character class when using (e)grep? – brgs – 2011-08-03T12:07:54.080