Possible Root URLS - regex

When validating URLs, I was wondering if the root could be setup like this:
http://my.great.web.site.I.rule.com/
I guess the real question is, if someone wanted to buy a .com with the name "some.site", would the above example be possible?
I was thinking something like that was out of the ordinary, and that the maximum would be something like this:
http://subdomain.mysite.com/
I might be thinking about this wrong, but I have very little knowledge of url structures and am trying to learn as much as I can.
Just wondering, because you could get a heck of a lot more precise with a regex expression like this (assuming periods cannot be used in domain/subdoamin names):
(https?:\/\/)([a-z0-9_-]{1,63}\.){1,2}([a-z]{2,8}){1}\/
then you could with this (assuming periods can be used in domain/subdomain names):
(https?:\/\/)([a-z0-9_-]{1,63}\.)\/
Any thoughts, or is this just ridiculous?


Wikipedia has good descriptions of URI schemas with links to all the relevant RFCs and Domain Names.
One note about your regex, you should also consider including port numbers when servers are hosted at non-default ports, e.g.
http://typicaltomcat.com:8080/
Edit: If you are looking for a regex to match URLs, there is interesting article on a liberal URL matcher.


Regarding the urls, you can have (in theory) up to 127 domains (counting the top level domain name .com), as long as the domain exceed 255 characters and each sub domain is less than 64 characters.

Related

Validate domain with regex but not subdomain

I couldn't find anywhere a regex that could validate a domain but not accepting subdomains.
I found a lot of rules that validates domains but unfortunately all of them also validates subdomains.
Anyone have tips on this?
I have this regex that is almost what I need:
/(?!www\.)(?=^.{5,254}$)(^(?:(?!\d+\.)[a-z0-9\-]{1,63}\.){1,2}(?:[a-z]{2,})$)/
If I use a subdomain like test.domain.com.br, it validates good (rejecting it), but test.domain.com don't.

I couldn't find anywhere a regex that could validate a domain but not accepting subdomains.
Because no regex can do that for you (and anyone pretending the opposite just doesn't understand the DNS).
Which is exactly why you found out that:
a lot of rules that validates domains but unfortunately all of them also validates subdomains.
Because a "subdomain" is just a domain seen differently (or you can say that any domain is also a subdomain of another domain, except for root and TLD). This is all because the DNS is a tree.
You can use the definition given in https://www.rfc-editor.org/rfc/rfc8499:
Subdomain: "A domain is a subdomain of another domain if it is
contained within that domain. This relationship can be tested by
seeing if the subdomain's name ends with the containing domain's
name." (Quoted from [RFC1034], Section 3.1) For example, in the
host name "nnn.mmm.example.com", both "mmm.example.com" and
"nnn.mmm.example.com" are subdomains of "example.com". Note that
the comparisons here are done on whole labels; that is,
"ooo.example.com" is not a subdomain of "oo.example.com".
You can not find administrative boundaries given an hostname by just looking at it. You need either to do DNS live queries to find the delegation points OR you need to use something like the Public Suffix List maintained by Mozilla. Both cases have drawbacks that can be or not a problem depending on your use case.
If you are not convinced, here is some list of valid hostnames (you can use them in an URL and it will work), and try to find out how a regex could have helped you by being right in all cases:
dk
www.sante.gouv.fr
www.com.com
www.nominet.co.uk
www.uk.com
www.walton.k12.fl.us
lagazettedesancetres.blogspot.fr
www.al.ma.leg.br
ab.m.wikibooks.nom.nu
1512f1.станок.спб.рус
You can obviously find shortcuts where a regex will still be wrong but good enough, if you restrict the cases you need to act on. Otherwise, if you need to stay generic and potentially work in any TLD, then, sorry, no regex will solve your problem.
Also your regex is wrong in multiple other cases. For example it won't handle IDN TLDs, that do exist, as they will be like xn--something in ASCII form which won't be accepted by [a-z]{2,}
BTW, useful terminologies I suggest using which may often be clearer than domain/subdomain, as taken from https://url.spec.whatwg.org/#host-miscellaneous
"A host’s public suffix is the portion of a host which is included on the Public Suffix List."
"A host’s registrable domain is a domain formed by the most specific public suffix, along with the domain label immediately preceding it, if any."
I think what you are searching is the "registrable domain" part of any given string (and as you can see from the algorithm given at above URL, you can't do that without finding first the public suffix, which you can't do without using an external resource, the information is NOT self contained in the string).

Regex to validate URL characters and all available TLDs

I'm new to regex and after few days of practicing/learning I manage to write URL validating regex.
/^((?:http|https)):\/\/(?=[a-z\d])((?:(?:(?!_|\.\.|-\.|\.-|\.\/|-\/)[\w-\.])+?)(?:[\.][a-z]{2,}))\/([\w-\.~:\/?#\[\]#!$&\'\(\)*+,;=]*)$/i
It works perfectly but problem was that I wanted to check all currently available TLDs because regex above doesn't validates unicode TLDs (XN--RHQV96G for example) because it allows only letters for domain. I can make it to validate unicode TLDs, but there is no point because it can't validate if entered TLD is real.
Since stackoverflow allows to answer your own question, I will include solution I came up with in my answer and I hope someone will find it usefull, but if you have better solution to solve this problem with TLDs, I will gladly choose your answer as accepted answer.
Rules are following:
Any localhost or IP based URLs shouldn't validate (http://localhost/ or http://8.8.8.8/ for example)
Any URL with authorization parameters or port in it, shouldn't validate (http://username#example.com/ or http://username:password#example.com/ or http://example.com:8080/ for example)
Only allowed protocols are http and https... If someone wants to validate ftp or something else, they can add ftp support easily (?:http|HTTP|ftp|FTP)

My solution is to get list of all currently available TLDs from IANA and include all of them in regex.
/^((?:http|https)):\/\/(?=[a-z\d])((?:(?:(?!_|\.\.|-\.|\.-|\.\/|-\/)[\w-\.])+?)(?:[\.](?:aaa|aarp|abb|abbott|abbvie|abogado|abudhabi|ac|academy|accenture|accountant|accountants|aco|active|actor|ad|adac|ads|adult|ae|aeg|aero|aetna|af|afl|ag|agakhan|agency|ai|aig|airbus|airforce|airtel|akdn|al|alibaba|alipay|allfinanz|ally|alsace|alstom|am|amica|amsterdam|analytics|android|anquan|ao|apartments|app|apple|aq|aquarelle|ar|aramco|archi|army|arpa|arte|as|asia|associates|at|attorney|au|auction|audi|audible|audio|author|auto|autos|avianca|aw|aws|ax|axa|az|azure|ba|baby|baidu|band|bank|bar|barcelona|barclaycard|barclays|barefoot|bargains|bauhaus|bayern|bb|bbc|bbva|bcg|bcn|bd|be|beats|beer|bentley|berlin|best|bet|bf|bg|bh|bharti|bi|bible|bid|bike|bing|bingo|bio|biz|bj|black|blackfriday|blog|bloomberg|blue|bm|bms|bmw|bn|bnl|bnpparibas|bo|boats|boehringer|bom|bond|boo|book|boots|bosch|bostik|bot|boutique|br|bradesco|bridgestone|broadway|broker|brother|brussels|bs|bt|budapest|bugatti|build|builders|business|buy|buzz|bv|bw|by|bz|bzh|ca|cab|cafe|cal|call|cam|camera|camp|cancerresearch|canon|capetown|capital|car|caravan|cards|care|career|careers|cars|cartier|casa|cash|casino|cat|catering|cba|cbn|cc|cd|ceb|center|ceo|cern|cf|cfa|cfd|cg|ch|chanel|channel|chase|chat|cheap|chintai|chloe|christmas|chrome|church|ci|cipriani|circle|cisco|citic|city|cityeats|ck|cl|claims|cleaning|click|clinic|clinique|clothing|cloud|club|clubmed|cm|cn|co|coach|codes|coffee|college|cologne|com|commbank|community|company|compare|computer|comsec|condos|construction|consulting|contact|contractors|cooking|cool|coop|corsica|country|coupon|coupons|courses|cr|credit|creditcard|creditunion|cricket|crown|crs|cruises|csc|cu|cuisinella|cv|cw|cx|cy|cymru|cyou|cz|dabur|dad|dance|date|dating|datsun|day|dclk|dds|de|deal|dealer|deals|degree|delivery|dell|deloitte|delta|democrat|dental|dentist|desi|design|dev|dhl|diamonds|diet|digital|direct|directory|discount|dj|dk|dm|dnp|do|docs|dog|doha|domains|dot|download|drive|dtv|dubai|dunlop|dupont|durban|dvag|dz|earth|eat|ec|edeka|edu|education|ee|eg|email|emerck|energy|engineer|engineering|enterprises|epost|epson|equipment|er|ericsson|erni|es|esq|estate|et|eu|eurovision|eus|events|everbank|exchange|expert|exposed|express|extraspace|fage|fail|fairwinds|faith|family|fan|fans|farm|fashion|fast|feedback|ferrero|fi|film|final|finance|financial|fire|firestone|firmdale|fish|fishing|fit|fitness|fj|fk|flickr|flights|flir|florist|flowers|flsmidth|fly|fm|fo|foo|football|ford|forex|forsale|forum|foundation|fox|fr|fresenius|frl|frogans|frontier|ftr|fund|furniture|futbol|fyi|ga|gal|gallery|gallo|gallup|game|games|garden|gb|gbiz|gd|gdn|ge|gea|gent|genting|gf|gg|ggee|gh|gi|gift|gifts|gives|giving|gl|glass|gle|global|globo|gm|gmail|gmbh|gmo|gmx|gn|gold|goldpoint|golf|goo|goodyear|goog|google|gop|got|gov|gp|gq|gr|grainger|graphics|gratis|green|gripe|group|gs|gt|gu|guardian|gucci|guge|guide|guitars|guru|gw|gy|hamburg|hangout|haus|hdfcbank|health|healthcare|help|helsinki|here|hermes|hiphop|hisamitsu|hitachi|hiv|hk|hkt|hm|hn|hockey|holdings|holiday|homedepot|homes|honda|horse|host|hosting|hoteles|hotmail|house|how|hr|hsbc|ht|htc|hu|hyundai|ibm|icbc|ice|icu|id|ie|ifm|iinet|il|im|imamat|imdb|immo|immobilien|in|industries|infiniti|info|ing|ink|institute|insurance|insure|int|international|investments|io|ipiranga|iq|ir|irish|is|iselect|ismaili|ist|istanbul|it|itau|iwc|jaguar|java|jcb|jcp|je|jetzt|jewelry|jlc|jll|jm|jmp|jnj|jo|jobs|joburg|jot|joy|jp|jpmorgan|jprs|juegos|kaufen|kddi|ke|kerryhotels|kerrylogistics|kerryproperties|kfh|kg|kh|ki|kia|kim|kinder|kindle|kitchen|kiwi|km|kn|koeln|komatsu|kosher|kp|kpmg|kpn|kr|krd|kred|kuokgroup|kw|ky|kyoto|kz|la|lacaixa|lamborghini|lamer|lancaster|land|landrover|lanxess|lasalle|lat|latrobe|law|lawyer|lb|lc|lds|lease|leclerc|legal|lego|lexus|lgbt|li|liaison|lidl|life|lifeinsurance|lifestyle|lighting|like|limited|limo|lincoln|linde|link|lipsy|live|living|lixil|lk|loan|loans|locker|locus|lol|london|lotte|lotto|love|lr|ls|lt|ltd|ltda|lu|lupin|luxe|luxury|lv|ly|ma|madrid|maif|maison|makeup|man|management|mango|market|marketing|markets|marriott|mattel|mba|mc|md|me|med|media|meet|melbourne|meme|memorial|men|menu|meo|metlife|mg|mh|miami|microsoft|mil|mini|mk|ml|mlb|mls|mm|mma|mn|mo|mobi|mobily|moda|moe|moi|mom|monash|money|montblanc|mormon|mortgage|moscow|motorcycles|mov|movie|movistar|mp|mq|mr|ms|mt|mtn|mtpc|mtr|mu|museum|mutual|mutuelle|mv|mw|mx|my|mz|na|nadex|nagoya|name|natura|navy|nc|ne|nec|net|netbank|netflix|network|neustar|new|news|next|nextdirect|nexus|nf|ng|ngo|nhk|ni|nico|nikon|ninja|nissan|nissay|nl|no|nokia|northwesternmutual|norton|now|nowruz|nowtv|np|nr|nra|nrw|ntt|nu|nyc|nz|obi|office|okinawa|olayan|olayangroup|ollo|om|omega|one|ong|onl|online|ooo|oracle|orange|org|organic|origins|osaka|otsuka|ott|ovh|pa|page|pamperedchef|panerai|paris|pars|partners|parts|party|passagens|pccw|pe|pet|pf|pg|ph|pharmacy|philips|photo|photography|photos|physio|piaget|pics|pictet|pictures|pid|pin|ping|pink|pioneer|pizza|pk|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This regex is huge (there is 1,348 TLDs), but it works perfectly and I can't find any wrong URL combination it will validate.
It allows only valid subdomains and it won't validate not allowed domain name combinations like http://.example.com/ or http://-exa..mple.com/
If you don't care about valid TLDs and only pattern is enough, you can use regex in original question, it's much smaller, faster and works pretty well.
Any answers and comments are welcome if you find any mistake or you can make this regex shorter or faster.
I will update this answer from time to time to include new TLDs from IANA database if there will be any.

Regex for matching different parts of a domain

I am attempting to split up domains into different categories (Subdomain, Domain, TLD) and am having trouble..
I can't figure out a way to match any number of subdomains and not overtake my domain or TLD mathcing. I am using PCRE regex.
Current regex:
\s(?:(?<subdomain>[a-z0-9\-]*){0,1}\.){0,3}(?<domain>(?>([a-z0-9\-]+)))\.(?<tld>[a-z\.]{2,6})\s
Data set:
apple.orange.banana.clevername.co.uk
strawberry.apple.orange.banana.clevername.co.uk
tangerine.com.au
simple.com
Note: There are spaces before and after the domains and they will always be lower case.
An example of how this data would match:
apple.orange.banana.clevername.co.uk
subdomain: apple.orange.banana
domain: google
tld: co.uk
If I add another fruit to the subdomain(strawberry.apple.orange.banana.clevername.co.uk), the match will fail. If I modify the {0,3} for the subdomain regex to a higher number or an unlimited number of matches, it gets too greedy and I no longer end up with a correct match for a domain/tld. Example of this:
Modified regex:
\s(?:(?<subdomain>[a-z0-9\-]*){0,1}\.){0,5}(?<domain>(?>([a-z0-9\-]+)))\.(?<tld>[a-z\.]{2,6})\s
Resulting match with new regex:
strawberry.apple.orange.banana.clevername.co.uk
subdomain: strawberry.apple.orange.banana.clevername
domain:
tld: co.uk
I'm sure the regex isn't the most efficient either so any help or suggestions would be greatly appreciated. Thanks!

I believe this should do it for you:
\s((?<subdomain>[a-z0-9\.\-]*)\.)?(?<domain>[a-z0-9\-]{3,}(?=\.[a-z\.]{3,6}))\.(?<tld>[a-z\.]{3,6})\s
Tested this in Splunk and it works with your test data set.
Do note that this won't work for very short domains like bit.ly because there is no way to tell the domain from the subdomain without doing a lookup of the TLD.
For example, compare something.bit.ly and clevername.com.au. Without outside information, there is no way to tell that bit and clevername are the domains.

I recently came across the same problem. So I took Syon's regex and modified it a bit. This is the result:
\s(?:(?<subdomain>[a-z0-9\.\-]*)\.)?(?<domain>(?!com)[a-z0-9\-]{3,}(?=\.[a-z\.]{2,}))\.(?:(?<tld>[a-z\.]{2,})$)\s
It works on the whole test data set (I trimmed the spaces though), as well as short domains like bit.ly. Also works for new top level domains like .cancerresearch. See result:
https://regex101.com/r/nX6yQ7/4
Note: The regex specifically states that the domain can't be com, this needs to be updated if other {3 characters}.xyz tlds need to be supported

You could try to find the longest suffix of the domain which is still listed in the Public Suffix List. After that, splitting the string should be easy.
Note that the list also considers domains of web hosters a public suffix. For example, in example.blogspot.com the public suffix is considered to be blogspot.com, not com. Also the list has to be parsed carefully as it contains comments and exceptions.

Writing Regular Expression for URL in Google Analytics

I have a huge list of URL's, in the format:
http://www.example.com/dest/uk/bath/
http://www.example.com/dest/aus/sydney/
http://www.example.com/dest/aus/
http://www.example.com/dest/uk/
http://www.example.com/dest/nor/
What RegEx could I use to get the last three URL's, but miss the first two, so that every URL without a city attached is given, but the ones with cities are denied?
Note: I am using Google Analytics, so I need to use RegEx's to monitor my URL's with their advanced feature. As of right now Google is rejecting each regular expression.

Generally, the best suggestion I can make for parsing URL's with a Regex is don't.
Your time is much much better spent finding a libary that exists for your language dedicated to the task of processing URLs.
It will have worked out all the edge cases, be fully RFC compliant, be bug free, secure, and have a great user interface so you can just suck out the bits you really want.
In your case, the suggested way to process it would be, using your URL library, extract the element s and then work explicitly on them.
That way, at most you'll have to deal with the path on its own, and not have to worry so much wether its
http://site.com/
https://site.com/
http://site.com:80/
http://www.site.com/
Unless you really want to.
For the "Path" you might even wish to use a splitter ( or a dedicated path parser ) to tokenise the path into elements first just to be sure.

tj111's current solution doesn't work - it matches all your urls.
Here's one that works (and I checked with your values). It also matches, no matter if there is a trailing slash or not:
http:\/\/.*dest\/\w+/?$

/http:\/\/www\.site\.com\/dest\/\w+\/?$/i
matches if they're all the same site with the "dest" there. you could also do this:
/\w+:\/\/[^/]+\/dest\/\w+\/?$/i
which will match any site with any protocal (http,ftp) and any site with the /dest/country at the end, and an optional /
Note, that this will only work with a subset of what the urls could legitimately be.

Try this regular expression:
^http://www\.example\.com/dest/[^/]+/$
This would only match the last three URLs.

Under what situations are regular expressions really the best way to solve the problem?

I'm not sure if Jeff coined it but it's the joke/saying that people who say "oh, I know I'll use regular expressions!" now have two problems. I've always taken this to mean that people use regular expressions in very inappropriate contexts.
However, under what circumstances are regular expressions really the best answer? What problems are they really the best or maybe only way to solve a situation?

RexExprs are good for:
Text Format Validations (email, url, numbers)
Text searchs/substitution.
Mappings (e.g. url pattern to function call)
Filtering some texts (related to substitution)
Lexical analysis during parsing.

They can be used to validate anything that have a pattern like :
Social Security Number
Telephone Number ( 555-555-5555 )
Email Address (something#example.com)
IP Address (but it's more complex to make sure it's valid)
All those have patterns and are easily verifiable by RegEx.
They are difficultly used for entry that have a logic instead of a pattern like a credit card number but they still can be used to do some client validation.
So the best ways?
To sanitize data entry on the client
side before sanitizing them on the
server.
To make "Search and Replace" of some
strings that contains pattern
I'm sure I am missing a lot of other cases.

Regular expressions are a great way to parse text that doesn't already have a parser (i.e. XML) I have used it to create a parser for the mod_rewrite syntax in the .htaccess file or in my URL Rewriter project http://www.codeplex.com/urlrewriter for example

they are really good when you want to be more specific than "*" or "?" like "3 letters then 2 numbers then a $ sign then a period"
The quote is from an anti-Perl rant from Jamie Zawinski. I think Perl used to do regex really badly but now it seems to be a standard engine for a lot of programs.
But the same sentiment still applies. If you don't know how to use regex, you better not try something real fancy other wise you get one of these tags too (see bronze list) ;o)
https://stackoverflow.com/users/730/keng

They are good for matching or finding text that takes a very specific and simple format. By "simple" I mean not nested and smaller than the entire html spec, for example.

They are primarily of value for highly structured text parsing. If you used named groups (and option in most mature regex systems), you have a phenomenally powerful and crisp way to handle the strings.
Here's an example. Consider that netstat in its various iterations on different linux OSes, and versions of netstat can return different results. Sometimes there is an extra column, sometimes there is a shift if the date/time format. Regexes give you a powerful way to handle that with a single expression. Couple that with named groups, and you can retrieve the data without hacks like:
1) split on spaces
2) ok, the netstat version is X so add I need to add 1 to all array references past column 5.
3) ok, the netstat version is Y so I need to make sure that I use multiple array references for the date info.
YUCK. Simple to fix in a Regex :-)