From: "Andreas S." <f@...>
Date: 2006-01-04T21:47:34+09:00
Subject: Re: Email Address Regex

Jacob Fugal wrote:
> On 1/3/06, Dan Kohn <dan@dankohn.com> wrote:
>> Here's a rails example for validating email addresses.
>>
>>   validates_format_of :login, :with => /
>>     ^[-^!$#%&'*+\/=?`{|}~.\w]+
>>     @[a-zA-Z0-9]([-a-zA-Z0-9]*[a-zA-Z0-9])*
>>     (\.[a-zA-Z0-9]([-a-zA-Z0-9]*[a-zA-Z0-9])*)+$/x,
>>     :message => "must be a valid email address",
>>     :on => :create
> 
> Be careful with email validation via regex, it's harder than you might
> think[1][2]:
> 
> /^([a-zA-Z0-9&_?\/`!|#*$^%=~{}+'-]+|"([\x00-\x0C\x0E-\x21\x23-\x5B\x5D
> -\x7F]|\\[\x00-\x7F])*")(\.([a-zA-Z0-9&_?\/`!|#*$^%=~{}+'-]+|"([\x00-\
> x0C\x0E-\x21\x23-\x5B\x5D-\x7F]|\\[\x00-\x7F])*"))*@([a-zA-Z0-9&_?\/`!
> |#*$^%=~{}+'-]+|\[([\x00-\x0C\x0E-\x5A\x5E-\x7F]|\\[\x00-\x7F])*\])(\.
> ([a-zA-Z0-9&_?\/`!|#*$^%=~{}+'-]+|\[([\x00-\x0C\x0E-\x5A\x5E-\x7F]|\\[
> \x00-\x7F])*\]))*$/

It is trivial to create a formally correct address that makes absolutely 
no sense, so what's the point of doing such a complicated and 
error-prone validation?

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