How do I deal with this regex issue?

Question

I need to extract a value from a hidden HTML field, have somewhat figured it out but I'm currently stuck.

My regex looks like:

<input type="hidden" name="form_id" value=".*"

But this extracts the whole string from the HTML.

The string looks like:

<input type="hidden" name="form_id" value="123"/>

I need to extract the "value" from the string, it is always changing, but the "name" is always the same. Is there a way to extract it without doing another expression? I appreciate any help.

@humble_coder Without creating another regex expression. I want to extract the value in one single expression(one line). — user1224096, Jul 02 '12 at 21:20
I'm sure I've got a T-shirt somewhere that says something about parsing HTML with regex........ — David Heffernan, Jul 02 '12 at 21:51
@DavidHeffernan, is that the one with the message spelled out in stab wounds? — Beta, Jul 02 '12 at 21:53
@David Heffernan if you can suggest me a free html parser component for delphi that is up to date, then I would use it. All the ones that work cost. — user1224096, Jul 02 '12 at 22:01
I always think about [`this post`](http://stackoverflow.com/a/1732454/960757). — TLama, Jul 02 '12 at 22:01
How much do the components cost? How much time will it take you to cobble something together yourself that's sufficiently robust? How much is your time worth? If X < Y * Z, then just buy the component and get on with the real part of your project. — Rob Kennedy, Jul 03 '12 at 04:43
@Beta - Does that shirt actually exist? Because I would buy it. — Justin Morgan - On strike, Jul 03 '12 at 18:44
@JustinMorgan, parse HTML with a regex and we'll come to your house and make one for you. — Beta, Jul 03 '12 at 19:04

score 3 · Accepted Answer · answered Jul 02 '12 at 22:51

3

(?<=<[^<>]+?name="form_id"[^<>]+value=")(.*)(?=")

answered Jul 02 '12 at 22:51

burning_LEGION

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humble_coder · Answer 2 · 2012-07-06T03:00:29.957

1

I just threw this together. Basically you want to negate any ending > in your request. So you'd likely want to do something of this nature:

<[^>]*hidden[^>]*value="(.*)"[^>]*>

And then read the first capture group (Delphi instructions). This keeps it as reasonably generic as possible although it does assume positional order on "hidden" and "value".

In order to find the value without regard for order you could use could use a slightly cleaner lookahead as was suggested:

 ^(?=.*name="form_id").*value="([^"]*)".*$

edited Jul 06 '12 at 03:00

answered Jul 02 '12 at 21:27

humble_coder

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Thanks, but this returns the whole string, not only the value. – user1224096 Jul 02 '12 at 21:43
The value is in the first capture group. Are you familiar with those? – humble_coder Jul 02 '12 at 21:45
Yeah I'm sorry, totally missed that one. The first capture group returns the value, do you mind posting an example if the order was changed? e.g if "value" came before "name" – user1224096 Jul 02 '12 at 21:58

score 0 · Answer 3 · edited Nov 25 '14 at 07:26

0

<[a-zA-Z"= _^>]*value="(\d*)"/>
I have tested this for your example.
If you want to extract for only input tag you can write:

<input[a-zA-Z"= _^>]*value="(\d*)"/>

edited Nov 25 '14 at 07:26

bummi

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answered Nov 25 '14 at 07:11

fhulprogrammer

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How do I deal with this regex issue?

3 Answers3