From: Matthew Smillie <M.B.Smillie@...>
Date: 2006-01-04T22:15:25+09:00
Subject: Re: Email Address Regex

On Jan 4, 2006, at 12:47, Andreas S. wrote:

> 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?

Job security?  I mean, without pointer arithmetic and its associated  
mysteries (negative array indices were a personal favourite), we need  
something to keep us gainfully employed!

matthew smillie.