4 ms·

actually you may want to make sure they have at least four characters separated by a dot, e.g. .\@\\.[..]+ ... and i think this is how the regex begins ... my

actually you may want to make sure they have at least four characters separated by a dot, e.g. .\@\\.[..]+ ... and i think this is how the regex begins ... my point though is that you can't send mail to a TLD, you need a domain name. and i don't think we have any one character TLDs. this is quickly turning into an exercise where you see how such a regex starts to happen. "well, then you have to consider this case ... and handle these exceptions ... and then enforce this ..."

derefr 14y ago
But you can send mail to, say, a machine listed as "a" in your hosts file.
Adirael 14y ago
And with the new personalized TLDs, wouldn't you be able to have something like ceo@nike? I just check for an @ and at least a character after and before it.
- meaty 14y ago
  Personally that pisses me off as it requires that I fully qualify all my local email addresses as what happens if I have the hostname 'nike' on my local net?
  - Adirael 14y ago
    It's going to get messy. I use a lot of hostnames which may end up being TLDs.
- xyzzy123 14y ago
  No. See: http://domainincite.com/10254-why-domain-names-need-punctuation http://domainincite.com/10254-why-domain-names-need-punctuat...
Jabbles 14y ago
my point though is that you can't send mail to a TLD You can: http://serverfault.com/questions/154991/why-do-some-tld-have-an-mx-record-on-the-zone-root-e-g-ai http://serverfault.com/questions/154991/why-do-some-tld-have... For instance the pope could get pope@va - if he wanted...
- xyzzy123 14y ago
  Try connecting to those on port 25, see if any accept mail... they don't tend to.
  - macspoofing 14y ago
    But they can. In this case, you probably won't alienate any of your potential users but as you add more and more arbitrary rules, you will.
    - xyzzy123 14y ago
      Fair call, I'm all for fewer arbitrary rules. Especially if it's less code. I still consider the "oh, but it's valid to have dotless on RHS!" to be one of those facts which is true, but irrelevant. Those three hypothetical users can't receive email sent from most major web providers (e.g. gmail, who don't allow dotless To:), can't sign up to most web sites (who get their validation wrong), and are at the mercy of pitiless local dns resolver rules (pope@va will go to pope@va.com for US users, a lot of the time).
  - VMG 14y ago
    Try connecting to those on port 25, see if any accept mail... they don't tend to. That's not a test for validating an email host either - looking up MX records would be more appropriate here.
    - xyzzy123 14y ago
      I actually meant the MXs, sort of thought that went without saying.
mootothemax 14y ago
you can't send mail to a TLD Not only is it possible, when I used to work for a company that administered a TLD, I did just that, sending and receiving email with the address t@TLD.
- anonymouz 14y ago
  Working for a TLD admistrator suddenly became much more desirable to me.
meaty 14y ago
I really don't care. We also, in automated test environments, send email to user@host so it doesn't escape the internal network. I don't have to use a regex if I use the methodology I specified. Simple Java implementation off the top of my head. Very fast, no imports or expression compilation required: bool isValidEmailAddress(String emailAddress) { int at = emailAddress.indexOf('@'); if (at < 1 || at == emailAddress.length() - 1) return false; return !Character.isWhiteSpace(emailAddress.charAt(at - 1)) && !Character.isWhiteSpace(emailAddress.charAt(at + 1)); } Improvements welcome. Should be portable to any other language trivially.
- readme 14y ago
  boolean isValid = (email != null ? email.contains("@") : false) the goal of client-side validation is to ensure that you can actually make that network call to do a real validation. the rfc is so complicated it's not even worth getting into this business, as evidenced by op's regex. would love to see some unit tests for that thing.
- meaty 14y ago
  C version because I was bored: int is_valid_email(char *email) { char *at = strstr(email, "@"); if (at <= email || at == strlen(email) + at - 2) return 0; return !isspace(*(at - 1)) && !isspace(*(at + 1)); } Test cases: assert(0 == is_valid_email("")); assert(0 == is_valid_email("@b")); assert(0 == is_valid_email("b@")); assert(0 == is_valid_email("d@ ")); assert(0 == is_valid_email(" @d")); assert(0 == is_valid_email(" ")); assert(1 == is_valid_email("a@b")); assert(1 == is_valid_email("John Smith <x.y@z.com>"));
- deleted 14y ago
  [deleted]
jnazario 14y ago
wow, thanks for the edumacation :) obviously didn't know soe of those things, and completely ignored the local domain bits.

derefr 14y ago

But you can send mail to, say, a machine listed as "a" in your hosts file.

Adirael 14y ago

And with the new personalized TLDs, wouldn't you be able to have something like ceo@nike? I just check for an @ and at least a character after and before it.

meaty 14y ago
Personally that pisses me off as it requires that I fully qualify all my local email addresses as what happens if I have the hostname 'nike' on my local net?
- Adirael 14y ago
  It's going to get messy. I use a lot of hostnames which may end up being TLDs.
xyzzy123 14y ago
No. See: http://domainincite.com/10254-why-domain-names-need-punctuation http://domainincite.com/10254-why-domain-names-need-punctuat...

Jabbles 14y ago

my point though is that you can't send mail to a TLD You can: http://serverfault.com/questions/154991/why-do-some-tld-have-an-mx-record-on-the-zone-root-e-g-ai http://serverfault.com/questions/154991/why-do-some-tld-have... For instance the pope could get pope@va - if he wanted...

xyzzy123 14y ago
Try connecting to those on port 25, see if any accept mail... they don't tend to.
- macspoofing 14y ago
  But they can. In this case, you probably won't alienate any of your potential users but as you add more and more arbitrary rules, you will.
  - xyzzy123 14y ago
    Fair call, I'm all for fewer arbitrary rules. Especially if it's less code. I still consider the "oh, but it's valid to have dotless on RHS!" to be one of those facts which is true, but irrelevant. Those three hypothetical users can't receive email sent from most major web providers (e.g. gmail, who don't allow dotless To:), can't sign up to most web sites (who get their validation wrong), and are at the mercy of pitiless local dns resolver rules (pope@va will go to pope@va.com for US users, a lot of the time).
- VMG 14y ago
  Try connecting to those on port 25, see if any accept mail... they don't tend to. That's not a test for validating an email host either - looking up MX records would be more appropriate here.
  - xyzzy123 14y ago
    I actually meant the MXs, sort of thought that went without saying.

mootothemax 14y ago

you can't send mail to a TLD Not only is it possible, when I used to work for a company that administered a TLD, I did just that, sending and receiving email with the address t@TLD.

anonymouz 14y ago
Working for a TLD admistrator suddenly became much more desirable to me.

meaty 14y ago

I really don't care. We also, in automated test environments, send email to user@host so it doesn't escape the internal network. I don't have to use a regex if I use the methodology I specified. Simple Java implementation off the top of my head. Very fast, no imports or expression compilation required: bool isValidEmailAddress(String emailAddress) { int at = emailAddress.indexOf('@'); if (at < 1 || at == emailAddress.length() - 1) return false; return !Character.isWhiteSpace(emailAddress.charAt(at - 1)) && !Character.isWhiteSpace(emailAddress.charAt(at + 1)); } Improvements welcome. Should be portable to any other language trivially.

readme 14y ago
boolean isValid = (email != null ? email.contains("@") : false) the goal of client-side validation is to ensure that you can actually make that network call to do a real validation. the rfc is so complicated it's not even worth getting into this business, as evidenced by op's regex. would love to see some unit tests for that thing.
meaty 14y ago
C version because I was bored: int is_valid_email(char *email) { char *at = strstr(email, "@"); if (at <= email || at == strlen(email) + at - 2) return 0; return !isspace(*(at - 1)) && !isspace(*(at + 1)); } Test cases: assert(0 == is_valid_email("")); assert(0 == is_valid_email("@b")); assert(0 == is_valid_email("b@")); assert(0 == is_valid_email("d@ ")); assert(0 == is_valid_email(" @d")); assert(0 == is_valid_email(" ")); assert(1 == is_valid_email("a@b")); assert(1 == is_valid_email("John Smith <x.y@z.com>"));
deleted 14y ago
[deleted]

jnazario 14y ago

wow, thanks for the edumacation :) obviously didn't know soe of those things, and completely ignored the local domain bits.