extract all email addresses from some .txt documents using ruby

Question

I have to extract all email addresses from some .txt documents. These emails may have these formats:

[email protected]
{a, b, c}@abc.edu
some other formats including some @ signs.

I choose ruby for my first language to write this program, but i don't know how to write the regex. Would someone help me? Thank you!

Related: [Extract email addresses from a block of text](http://stackoverflow.com/questions/504860/extract-email-addresses-from-a-block-of-text) — miku, Jul 07 '10 at 11:55
I was about to suggest extracting all nonspace char-sequences with `@` in them - but it wouldn't work for your second example. — Amarghosh, Jul 07 '10 at 12:31

score 6 · Accepted Answer · answered Jul 10 '10 at 01:42

6

Depending on the nature of your .txt documents, you don't have to use one of the complicated regexes that attempt to validate email addresses. You're not trying to validate anything. You're just trying to grab what's already there. Generally speaking, a regex to grab what's already there can be much simpler than a regex that needs to validate input.

An important question is whether your .txt documents contain @ signs that are not part of an email address you want to extract.

This regex handles your first two requirements:

\w+@[\w.-]+|\{(?:\w+, *)+\w+\}@[\w.-]+

Or if you want to allow any sequence of non-space characters containing an @ sign, plus your second requirement (which has spaces):

\S+@\S+|\{(?:\w+, *)+\w+\}@[\w.-]+

answered Jul 10 '10 at 01:42

Jan Goyvaerts

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Take care.. It will noch accept "-" inside mail addresses – gies0r Oct 21 '16 at 10:51
nor will it accept "." before the @ sign. So [email protected] => [email protected] – Eskim0 Jun 29 '17 at 00:24
This is an answer to Ikbear's question about his/her specific requirements. It is NOT a general-purpose guide on how to match email addresses with regexes. If you read my article at http://www.regular-expressions.info/email.html then you'll learn that there are always trade-offs. – Jan Goyvaerts Jun 29 '17 at 06:39

score 2 · Answer 2 · answered Jul 07 '10 at 12:03

Have a look at this rather in-depth analysis:

Upshot is use this regular expression:

/^([\w\!\#$\%\&\'\*\+\-\/\=\?\^\`{\|\}\~]+\.)*[\w\!\#$\%\&\'\*\+\-\/\=\?\^\`{\|\}\~]+@((((([a-z0-9]{1}[a-z0-9\-]{0,62}[a-z0-9]{1})|[a-z])\.)+[a-z]{2,6})|(\d{1,3}\.){3}\d{1,3}(\:\d{1,5})?)$/i

score 1 · Answer 3 · answered Jun 29 '17 at 00:27

1

Found this at https://www.shellhacks.com/regex-find-email-addresses-file-grep/ which met my needs:

\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,6}\b

answered Jun 29 '17 at 00:27

Eskim0

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This regex does not meet Ikbear's requirement #2. It also matches [email protected] and fails to match emails on new TLDs such as .solutions that are longer than 6 characters. Great if this regex meets your needs, but not an answer to this question, and not a good general-purpose email regex in 2017. – Jan Goyvaerts Jun 29 '17 at 06:46

extract all email addresses from some .txt documents using ruby

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