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Regular Expressions Cookbook, 2nd Edition
book

Regular Expressions Cookbook, 2nd Edition

by Jan Goyvaerts, Steven Levithan
August 2012
Intermediate to advanced content levelIntermediate to advanced
609 pages
19h 16m
English
O'Reilly Media, Inc.
Content preview from Regular Expressions Cookbook, 2nd Edition

4.1. Validate Email Addresses

Problem

You have a form on your website or a dialog box in your application that asks the user for an email address. You want to use a regular expression to validate this email address before trying to send email to it. This reduces the number of emails returned to you as undeliverable.

Solution

Simple

This first solution does a very simple check. It only validates that the string contains an at sign (@) that is preceded and followed by one or more nonwhitespace characters.

^\S+@\S+$
Regex options: None
Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python
\A\S+@\S+\Z
Regex options: None
Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby

Simple, with restrictions on characters

The domain name, the part after the @ sign, is restricted to characters allowed in domain names. Internationalized domain names are not allowed. The local part, the part before the @ sign, is restricted to characters commonly used in email local parts, which is more restrictive than what most email clients and servers will accept:

^[A-Z0-9+_.-]+@[A-Z0-9.-]+$
Regex options: Case insensitive
Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python
\A[A-Z0-9+_.-]+@[A-Z0-9.-]+\Z
Regex options: Case insensitive
Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby

Simple, with all valid local part characters

This regular expression expands the previous one by allowing a larger set of rarely used characters in the local part. Not all email software can handle all these characters, but we’ve included ...

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Publisher Resources

ISBN: 9781449327453Supplemental ContentErrata Page