I am still figuring my way around regex and have come across a problem that I am trying to solve. How do I validate for multiple specific email addresses?
For example, I want to only allow testdomain.com, realdomain.com, gooddomain.com to be validated. All other email addresses are not allowed.
annie#testdomain.com OK
aaron1#realdomain.com OK
amber#gooddomain.com OK
annie#otherdomain.com NOT OK
But I'm stil unclear on how to add multiple specific email addresses for the regex.
Any and all help would be appreciated.
Thank you,
Do you mean to include various ligitimate domains in one regex?
\b[A-Z0-9._%-]+#(testdomain|gooddomain|realdomain)\.com\b
You didn't specify which language you're using, but most regex implementations have a notion of logical operators, so the domain part of your pattern would have something like:
(domain1|domain2|domain3)
\b[A-Z0-9._%-]+#(testdomain|realdomain|gooddomain)\.com\b
Assuming the above works for testdomain:
\b[A-Z0-9._%-]+#(?:testdomain|realdomain|gooddomain)\.com\b
Also, please note that you will have to add a case insensitive i modifier for this to work with your test cases, or use [A-Za-z0-9._%-] instead of [A-Z0-9._%-]
See here
To make this expandable to many domains, I would probably capture the domain name and then compare that captured domain name with your whitelist in code.
.+#(.+)
First, ".+" will match any number (more than 0) of any characters up until the last "#" symobol in the string.
Second, "#" will match the "#" symbol.
Third, "(.+)" will match and capture (capture because of the parenthesis) any character string after the "#" symbol.
Then, depending on the language you are using, you can get the captured string. Then you can see if that captured string is in your domain whitelist. Note, you'll want to do a case insensitive comparison in this last step.
The official standard is known as RFC 2822.
Use OR operator | for all domain names you want to allow. Do not forget to escape . in the domain.
[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*#(?:testdomain\.com|realdomain\.com|gooddomain\.com)
Also use case-insensitivity modifier/flag to allow capital letters in the address.
Related
I'm new to regex. I need to find instances of example.com in an .SQL file in Notepad++ without those instances being part of subdomain.example.com(edited)
From this answer, I've tried using ^((?!subdomain))\.example\.com$, but this does not work.
I tested this in Notepad++ and # https://regex101.com/r/kS1nQ4/1 but it doesn't work.
Help appreciated.
Simple
^example\.com$
with g,m,i switches will work for you.
https://regex101.com/r/sJ5fE9/1
If the matching should be done somewhere in the middle of the string you can use negative look behind to check that there is no dot before:
(?<!\.)example\.com
https://regex101.com/r/sJ5fE9/2
Without access to example text, it's a bit hard to guess what you really need, but the regular expression
(^|\s)example\.com\>
will find example.com where it is preceded by nothing or by whitespace, and followed by a word boundary. (You could still get a false match on example.com.pk because the period is a word boundary. Provide better examples in your question if you want better answers.)
If you specifically want to use a lookaround, the neative lookahead you used (as the name implies) specifies what the regex should not match at this point. So (?!subdomain\.)example trivially matches always, because example is not subdomain. -- the negative lookahead can't not be true.
You might be better served by a lookbehind:
(?<!subdomain\.)example\.com
Demo: https://regex101.com/r/kS1nQ4/3
Here's a solution that takes into account the protocols/prefixes,
/^(www\.)?(http:\/\/www\.)?(https:\/\/www\.)?example\.com$/
So im using this function here:
function get_domain($url)
{
$pieces = parse_url($url);
$domain = isset($pieces['host']) ? $pieces['host'] : '';
if (preg_match('/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i', $domain, $regs)) {
return $regs['domain'];
}
return false;
}
$referer = get_domain($_SERVER['HTTP_REFERER']);
And what i need is another regex for it, if someone would be so kind to help.
Exactly what i need is for it to get the whole domain, including subdomains.
Lets say as a real problem i have now. When people blogging link from example: myblog.blogger.com
The referer url will be just blogger.com, which is not ideal..
So if someone could help me so i can get the including subdomain as regex code for the function above, id apreciate it alot!
Thanks!
This regex should match a domain in a string, including any dubdomains:
/([a-z0-9|-]+\.)*[a-z0-9|-]+\.[a-z]+/
Translated to rough english, it functions like this: "match the first part of the string that has 'sometextornumbers.sometext', and also include any number of 'sometextornumbers.' that might preceed it.
See it in action here: http://regexr.com?2vppk
Note that the multiline and global flags in that link are only there to be able to match the entire blob of test-text, so you don't need if you're passing only one line to the regex
Good luck with the above as Domain names now contain non-roman characters. These would have to be processed into equivalent but unique ascii before regex could work reliably. See RFC 3490 Internationalizing Domain Names in Applications (IDNA) ...
See https://www.rfc-editor.org/rfc/rfc3490
which has
Until now, there has been no standard method for domain names to use
characters outside the ASCII repertoire. This document defines
internationalized domain names (IDNs) and a mechanism called
Internationalizing Domain Names in Applications (IDNA) for handling
them in a standard fashion. IDNs use characters drawn from a large
repertoire (Unicode), but IDNA allows the non-ASCII characters to be
represented using only the ASCII characters already allowed in so-
called host names today. This backward-compatible representation is
required in existing protocols like DNS, so that IDNs can be
introduced with no changes to the existing infrastructure. IDNA is
only meant for processing domain names, not free text.
I guess this is an optimization for the first suggestion.
The main improvements:
does not react to invalid pattern sub..domain.xyz
captures more that one sub-domain as group
captures port if given
https://((?:[a-z0-9-]+\.)*)([a-z0-9-]+\.[a-z]+)($|\s|\:\d{1,5})
Test it: https://regex101.com/r/njFIil/1
This regex does not handle any unicode symbols, which could be a problem as mentioned above.
Better solution:
/^([a-z0-9|-]+[a-z0-9]{1,}\.)*[a-z0-9|-]+[a-z0-9]{1,}\.[a-z]{2,}$/
Regex sample:
https://regexr.com/4k71a
And for email address:
/^[a-z0-9|.|-]+[a-z0-9]{1,}#([a-z0-9|-]+[a-z0-9]{1,}\.)*[a-z0-9|-]+[a-z0-9]{1,}\.[a-z]{2,}$/
I have a regex pattern for URL's that I use to check for links in a body of text. The only problem is that the pattern will match this link
stackoverflow.com
And this sentence
I'm a sentence.Next Sentence.
Obviously this would make sense because my pattern doesn't strong check .com, .co.uk, .com.au etc
I want it to match stackoverflow.com and not the latter.
As I'm no Regex expert, does anyone know of any good Regex patterns for checking for all types of URL's in a body text, while not matching the sentences like above?
If I have to strong check the domain extension, I suppose I'll have to settle.
Here's my pattern, but i don't think it help.
(([\w]+:)?\/\/)?(([\d\w]|%[a-fA-f\d]{2,2})+(:([\d\w]|%[a-fA-f\d]{2,2})+)?#)?([\d\w][-\d\w]{0,253}[\d\w]\.)+[\w]{2,4}(:[\d]+)?(\/([-+_~.\d\w]|%[a-fA-f\d]{2,2})*)*(\?(&?([-+_~.\d\w]|%[a-fA-f\d]{2,2})=?)*)?(#([-+_~.\d\w]|%[a-fA-f\d]{2,2})*)?
I would definitely suggest finding a working regex that someone else has made (which would probably include a strong check on the domain extension), but here is one possible way to just modify your existing regex.
It requires that you make the assumption that usually links will not mix case in the domain extension, for example you might see .COM or .com but probably not .Com, if you only match domain extensions that don't mix case then you would avoid matching most sentences.
In the middle of your regex you have [\w]{2,4}, try changing this to ([A-Z]{2,4}|[a-z]{2,4}) (or (?:[A-Z]{2,4}|[a-z]{2,4}) if you don't want a new captured group).
I have the following regex.
^((?!example).)*$#Subdomain is reserved (example).
I would like to validate <subdomain>.example.org. However, since the domain name contains example, a match is occurring.
The validation should not match when the address is www.example.org
The validation should match when the address is example.example.org
Looks like you're missing the escape character from the period
^(example)\..*$
should work
It seems that a simple
^example\.
is enough. Or use string methods, depending on your language:
url.indexOf('example.') === 0
If input such as example.org is also possible, you can use
^example\..+\.
to force the appearance of two dots. But this would still fail for example.co.uk. It depends on your input.
A simple way might be to break it up into two:
^.+\.example\.org$
^(www)?\.example\.org$
If 1) matches and 2) does not, it's a subdomain of example.org; otherwise, it's not. (Although www technically is a subdomain, but you understand.)
I'm looking for the regex to validate hostnames. It must completely conform to the standard. Right now, I have
^[0-9a-z]([0-9a-z\-]{0,61}[0-9a-z])?(\.[0-9a-z](0-9a-z\-]{0,61}[0-9a-z])?)*$
but it allows successive hypens and hostnames longer than 255 characters. If the perfect regex is impossible, say so.
Edit/Clarification: a Google search didn't reveal that this is a solved (or proven unsolvable) problem. I want to to create the definitive regex so that nobody has to write his own ever. If dialects matter, I want a a version for each one in which this can be done.
^(?=.{1,255}$)[0-9A-Za-z](?:(?:[0-9A-Za-z]|-){0,61}[0-9A-Za-z])?(?:\.[0-9A-Za-z](?:(?:[0-9A-Za-z]|-){0,61}[0-9A-Za-z])?)*\.?$
The approved answer validates invalid hostnames containing multiple dots (example..com). Here is a regex I came up with that I think exactly matches what is allowable under RFC requirements (minus an ending "." supported by some resolvers to short-circuit relative naming and force FQDN resolution).
Spec:
<hname> ::= <name>*["."<name>]
<name> ::= <letter-or-digit>[*[<letter-or-digit-or-hyphen>]<letter-or-digit>]
Regex:
^([a-zA-Z0-9](?:(?:[a-zA-Z0-9-]*|(?<!-)\.(?![-.]))*[a-zA-Z0-9]+)?)$
I've tested quite a few permutations myself, I think it is accurate.
This regex also does not do length validation. Length constraints on labels betweens dots and on names are required by RFC, but lengths can easily be checked as second and third passes after validating against this regex, by checking full string length, and by splitting on "." and validating all substrings lengths. E.g., in JavaScript, label length validation might look like: "example.com".split(".").reduce(function (prev, curr) { return prev && curr.length <= 63; }, true).
Alternative Regex (without negative lookbehind, courtesy of the HTML Living Standard):
^[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$
Your answer was relatively close.
But see
RFC 2396 Section 3.2.2
JaredPar's reference to this answer is referring to Regexp/Common/URI/RFC2396.pm source.
For a hostname RE, that perl module produces
(?:(?:(?:(?:[a-zA-Z0-9][-a-zA-Z0-9]*)?[a-zA-Z0-9])[.])*(?:[a-zA-Z][-a-zA-Z0-9]*[a-zA-Z0-9]|[a-zA-Z])[.]?)
I would modify to be more accurate as:
(?:(?:(?:(?:[a-zA-Z0-9][-a-zA-Z0-9]{0,61})?[a-zA-Z0-9])[.])*(?:[a-zA-Z][-a-zA-Z0-9]{0,61}[a-zA-Z0-9]|[a-zA-Z])[.]?)
Optionally anchoring the ends with ^$ to ONLY match hostnames.
I don't think a single RE can accomplish an full validation because, according to Wikipedia, there is a 255 character length restriction which i don't think can be included within that same RE, at least not without a ton of changes, but it's easy enough to just check the length <= 255 before running the RE.
Take a look at the following question. A few of the answers have regex expressions for host names
Regular expression to match DNS hostname or IP Address?
Could you specify what language you want to use this regex in? Most languages / systems have slightly different regex implementations that will affect people's answers.
I tried all answers with these examples below and unfortunately no one has passed the test.
ec2-11-111-222-333.cd-blahblah-1.compute.amazonaws.com
domaine.com
subdomain.domain.com
12533d5.dkkkd.com
2dotsextension.co
1dotextension.c
ekkej_dhh.com
12552.2225
112.25.25
12345.com
12345.123.com
domaine.123
whatever
9999-ee.99
email#domain.com
.jjdj.kkd
-subdomain.domain.com
#subdomain.domain.com
112.25.25
Here is a better solution.
^[A-Za-z0-9][A-Za-z0-9-.]*\.\D{2,4}$
Just please post any other not considered case if exists # https://regex101.com/r/89zZkW/1
What about:
^(?=.{1,255})([0-9A-Za-z]|_{1}|\*{1}$)(?:(?:[0-9A-Za-z]|\b-){0,61}[0-9A-Za-z])?(?:\.[0-9A-Za-z](?:(?:[0-9A-Za-z]|\b-){0,61}[0-9A-Za-z])?)*\.?$
for matching only one '_' (for some SRV) at the beginning and only one * (in case of a label for a DNs wildcard)
According to the relevant internet RFCs and assuming you have lookahead and lookbehind positive and negative assertions:
If you want to validate a local/leaf hostname for use in an internet hostname (e.g. - FQDN), then:
^(?!-)[-a-zA-Z0-9]{1,63}(?<!-)$
That ^^^ is also the general check that a label component inside an internet hostname is valid.
If you want to validate an internet hostname (e.g. - FQDN), then:
^(?=.{1,253}\.?$)(?:(?!-)[-a-zA-Z0-9]{1,63}(?<!-)\.)*(?!-)[-a-zA-Z0-9]{1,63}(?<!-)\.?$