Zašto ne treba parsirati (X)HTML regexom

[Dušan Dželebdžić]

Jedan probao, pa odlepio...
http://stackoverflow.com/a/1732454

You can't parse [X]HTML with regex. Because HTML can't be parsed by regex. Regex is not a tool that can be used to correctly parse HTML. As I have answered in HTML-and-regex questions here so many times before, the use of regex will not allow you to consume HTML. Regular expressions are a tool that is insufficiently sophisticated to understand the constructs employed by HTML. HTML is not a regular language and hence cannot be parsed by regular expressions. Regex queries are not equipped to break down HTML into its meaningful parts. so many times but it is not getting to me. Even enhanced irregular regular expressions as used by Perl are not up to the task of parsing HTML. You will never make me crack. HTML is a language of sufficient complexity that it cannot be parsed by regular expressions. Even Jon Skeet cannot parse HTML using regular expressions. Every time you attempt to parse HTML with regular expressions, the unholy child weeps the blood of virgins, and Russian hackers pwn your webapp. Parsing HTML with regex summons tainted souls into the realm of the living. HTML and regex go together like love, marriage, and ritual infanticide. The <center> cannot hold it is too late. The force of regex and HTML together in the same conceptual space will destroy your mind like so much watery putty. If you parse HTML with regex you are giving in to Them and their blasphemous ways which doom us all to inhuman toil for the One whose Name cannot be expressed in the Basic Multilingual Plane, he comes. HTML-plus-regexp will liquify the n​erves of the sentient whilst you observe, your psyche withering in the onslaught of horror. Rege̿̔̉x-based HTML parsers are the cancer that is killing StackOverflow it is too late it is too late we cannot be saved the trangession of a chi͡ld ensures regex will consume all living tissue (except for HTML which it cannot, as previously prophesied) dear lord help us how can anyone survive this scourge using regex to parse HTML has doomed humanity to an eternity of dread torture and security holes using regex as a tool to process HTML establishes a breach between this world and the dread realm of c͒ͪo͛ͫrrupt entities (like SGML entities, but more corrupt) a mere glimpse of the world of reg​ex parsers for HTML will ins​tantly transport a programmer's consciousness into a world of ceaseless screaming, he comes, the pestilent slithy regex-infection wil​l devour your HT​ML parser, application and existence for all time like Visual Basic only worse he comes he comes do not fi​ght he com̡e̶s, ̕h̵i​s un̨ho͞ly radiańcé destro҉ying all enli̍̈́̂̈́ghtenment, HTML tags lea͠ki̧n͘g fr̶ǫm ̡yo​͟ur eye͢s̸ ̛l̕ik͏e liq​uid pain, the song of re̸gular exp​ression parsing will exti​nguish the voices of mor​tal man from the sp​here I can see it can you see ̲͚̖͔̙î̩́t̲͎̩̱͔́̋̀ it is beautiful t​he final snuffing of the lie​s of Man ALL IS LOŚ͖̩͇̗̪̏̈́T ALL I​S LOST the pon̷y he comes he c̶̮omes he comes the ich​or permeates all MY FACE MY FACE ᵒh god no NO NOO̼O​O NΘ stop the an​*̶͑̾̾​̅ͫ͏̙̤g͇̫͛͆̾ͫ̑͆l͖͉̗̩̳̟̍ͫͥͨe̠̅s ͎a̧͈͖r̽̾̈́͒͑e n​ot rè̑ͧ̌aͨl̘̝̙̃ͤ͂̾̆ ZA̡͊͠͝LGΌ ISͮ̂҉̯͈͕̹̘̱ TO͇̹̺ͅƝ̴ȳ̳ TH̘Ë͖́̉ ͠P̯͍̭O̚​N̐Y̡ H̸̡̪̯ͨ͊̽̅̾̎Ȩ̬̩̾͛ͪ̈́̀́͘ ̶̧̨̱̹̭̯ͧ̾ͬC̷̙̲̝͖ͭ̏ͥͮ͟Oͮ͏̮̪̝͍M̲̖͊̒ͪͩͬ̚̚͜Ȇ̴̟̟͙̞ͩ͌͝S ̨̥̫͎̭ͯ̿̔̀ͅ

[mileusna]

a u komentarima

Chuck Norris can parse HTML with regex. – THX-1138 Nov 14 '09 at 0:03

[webarto]

http://www.codinghorror.com/blog/200...hulhu-way.html puk'o je bobince ima već 2 godine

[ivanhoe]

funny, ali to je potpuni bull****... html ne treba parsirati regexp-om:
a) ako ne znas makar priblizno kako izgleda doticni HTML
b) ako ne znas da koristis regexp-e

ali svakako radi bolje od parsiranja XML parserima, jer to ne radi uopste sem sa staticnim i 100% validnim stranama.. cim probas tako da pocupas podatke iz nekog e-shopa ili CMS-a i krenes da naleces na random tagove koje je neko slucajno pesjtvovao u sred texta, you're screwed with XML...

[jablan]

Originalno napisao ivanhoe

jer to ne radi uopste sem sa staticnim i 100% validnim stranama..

Umm...

http://nokogiri.org/tutorials/ensuri...ed_markup.html

[akubra]

Za dobar HTML parser su bitne samo 2 stvari: da radi posao i da moze da se napravi za sto krace vreme. U vecini prakticnih situacija regexp to radi odlicno.

[djipko]

Da se nadovezem na Jablana - beautiful soup (http://www.crummy.com/software/BeautifulSoup/) za Python ce ti isto isparsirati stagod mu das, makar proslo pored validnosti nije. Siguran sam da ima nesto slicnog stepena robustnosti i za PHP i ostale...

[Dušan Dželebdžić]

Originalno napisao ivanhoe

ali svakako radi bolje od parsiranja XML parserima, jer to ne radi uopste sem sa staticnim i 100% validnim stranama..

Juče sam tek malo ozbiljnije pogledao dokumentaciju za ovo (juče mi je prvi put zatrebalo ), ali čini mi se da je u PHP-u to fino rešeno. Domdocument ima metod loadXML koji očekuje savršeno formatiran kôd, ali tu je i loadHTML koji radi isto, samo ne paniči ako fali neki tag.

http://www.php.net/manual/en/domdocument.loadhtml.php

The function parses the HTML contained in the string source. Unlike loading XML, HTML does not have to be well-formed to load. This function may also be called statically to load and create a DOMDocument object. The static invocation may be used when no DOMDocument properties need to be set prior to loading.

[ivanhoe]

Moram da priznam da sam ja radio scrapping podataka samo iz perla i to zadnji put pre par godina, tako da mozda sad i postoji neko efikasno resenje, tada definitivno nije postojalo nista sto moze da se nosi sa custom napisanim regExp-om po pitanju brzine i efikasnosti...

Kad se spajderuju podaci obicno ti je potrebno samo par cifara od cele HTML strane, parsiranje svega toga u DOM da bi dohvatio par celija iz neke tabele je jako neefikasan pristup IMHO... i ne samo neefikasan, nego i nepotreban, zasto bi to radio? A u realnom slucaju kad sve to pustis u X procesa koji treba da obrade katalog od 500-600 hiljada artikala u nekom razumnom roku, onda memorija i brzina postaju vrlo velika stavka...

[mileusna]

Ja verujem da postoje bolja rešenja, ali navika je čudo, tako da ja i dalje radim putem RegExp.