Trying to figure out Regular Expression syntax regarding the Single Quote

Question

I am working on a presentation regarding Regular Expressions. While trying to break down the expression for an Internet Email Address I have figured out what most of it is aside from the single quote ('). Any assistance would be greatly appreciated. The expression is as follows.

\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*

http://stackoverflow.com/questions/201323/using-a-regular-expression-to-validate-an-email-address — Guvante, Jun 10 '13 at 18:00
I don't think he means that he has a problem - he simply wants to know what the symbol means. — IanPudney, Jun 10 '13 at 18:01
This is pretty heavily dependent on the language... or are you wondering what the single quote does? — FrankieTheKneeMan, Jun 10 '13 at 18:01
I am just trying to get the syntax down. I understand and have found definitions for \w, (), [] and so on but not for the single quote. Also I am working in C#. — Tom, Jun 10 '13 at 18:02
Single quotes aren't syntactically significant in regular expressions. It's just a literal `'`. — Cairnarvon, Jun 10 '13 at 18:02

arshajii · Answer 1 · 2013-06-10T18:06:46.090

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' has no special meaning. The regular expression just says that single quotes can be in a valid e-mail address's username, so as long as they come after at least one word character and before at least one word character. For example this is a valid address, according to this regex: a'b'c@xyz.com.

edited Jun 10 '13 at 18:06

answered Jun 10 '13 at 18:01

arshajii

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Thanks very much. This was quite helpful. – Tom Jun 10 '13 at 18:32

score 0 · Accepted Answer · edited Oct 07 '21 at 06:16

This expression does not correspond very well to the actual address specification, but it is true that ' is just an ordinary allowed character in the local part of an email address, and that's presumably why the RE includes it.

In fact, ' can begin or end an address so it's incorrect for that RE to insist that it appear only within the local part. OTOH, . cannot begin or end the local part, so it's somewhat correct that the RE insists it be surrounded by word characters.

(A fairly easy-to-read informational RFC that describes address syntax is RFC 3696.)

score 0 · Answer 3 · answered Jun 10 '13 at 18:22

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Anything inside of the brackets is literally allowed, so they're literally accepting an apostrophe for cases where you would have a name like:

c.o'neil@somewebsite.com

answered Jun 10 '13 at 18:22

AbsoluteƵERØ

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Trying to figure out Regular Expression syntax regarding the Single Quote

3 Answers3