this post was submitted on 29 Feb 2024
338 points (96.2% liked)

linuxmemes

20758 readers
926 users here now

I use Arch btw

Sister communities:

Community rules

  1. Follow the site-wide rules and code of conduct
  2. Be civil
  3. Post Linux-related content
  4. No recent reposts

Please report posts and comments that break these rules!

founded 1 year ago
MODERATORS
poopsmith
zephyr
338
Parsing HTML with regex (lemmy.sdf.org)
submitted 6 months ago by [email protected] to c/linuxmemes
40 comments fedilink hide all child comments
 

cross-posted from: https://lemmy.sdf.org/post/12950329

you are viewing a single comment's thread
view the rest of the comments
[–] [email protected] 29 points 6 months ago (2 children)

I use regex in SQL to parse HTML stored in a database. It can't universally parse and validate every HTML document, but it can still be used to find specific data like pulling out every link.

[–] BluesF 15 points 6 months ago (1 children)

I don't think that using regex to basically do regex stuff on strings that happen to also be HTML really counts as parsing HTML

[–] [email protected] 5 points 6 months ago* (last edited 6 months ago) (1 children)

I guess it depends on your definition of "parse", but let me tell you it's still very painful to deal with things like attributes appearing in any order inside of a tag so I definitely am not advocating to use regex to "read" (or whatever you want to call it) HTML.

[–] fuckwit_mcbumcrumble 3 points 6 months ago* (last edited 6 months ago)

My regex at work is full of (<[^>]+\s*){0,5} because we don’t care about 90 percent of the attributes. All we care is it’s class=“data I want” and eventually take me to that data.

[–] hperrin 11 points 6 months ago* (last edited 6 months ago) (1 children)

Technically, regex can’t pull out every link in an HTML document without potentially pulling fake links.

Take this example (using curly braces instead of angle brackets, because html is valid markdown):

{template id="link-template"}
    {a href="javascript:void(0);"}link{/a}
{/template}

That’s perfectly valid HTML, but you wouldn’t want to pull that link out, and POSIX regex can’t really avoid it. At least not with just a single regex. Imagine a link nested within like 3 template tags.

[–] [email protected] 3 points 6 months ago (1 children)

Yes, I said in my original comment that it can't universally parse and validate every HTML document. If they're older pages that don't do lots of crazy formatting then it's not too hard to use regex as a first pass then take a second pass through the results to weed out the odd stuff.

[–] hperrin 8 points 6 months ago* (last edited 6 months ago)

I would argue that that is not parsing. That’s just pattern matching. For something to be parsing a document, it would have to have some “understanding” of the structure of the document. Since regex is not powerful enough to correctly “understand” the document, it’s not parsing.