# Hpricot elem index/position

**URL:** <https://www.ruby-forum.com/t/hpricot-elem-index-position/150261>\
**Category:** Ruby\
**Created:** [October 6, 2008, 6:12pm UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261 "2008-10-06T18:12:44Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 6, 2008, 6:12pm UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261/1 "2008-10-06T18:12:44Z")

</div>

Hey,

Trying to find the String index of an Hpricot::Elem within its doc.  
For example…

doc = Hpricot(“bobjamesdan”)  
elem = doc.search(“a”)[1]  
elem.start #=\> 10 ( the first ‘\<’ of the second a tag.)

and eventually the following would be good…

elem.length #=\> 12  
elem.end #=\> 21

Any thoughts appreciated!  
Henners

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 6, 2008, 10:55pm UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261/2 "2008-10-06T22:55:01Z")

</div>

On Oct 6, 10:19 am, “removed\_email\_address@domain.invalid”  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> elem.length #=\> 12  
> elem.end #=\> 21
> 
> Any thoughts appreciated!  
> Henners

My first thought is: Why do you want that information? Character  
position is meaningless in an XML and HTML DOM. Whitespace can change  
character positions without affecting the DOM at all.

– Mark.

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 7, 2008, 10:00am UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261/3 "2008-10-07T10:00:38Z")

</div>

Hi Mark,

I’m writing a broken link reporting type tool. When I find a dodgy tag  
I’d like to be able to relay the character position and or line number  
to the user. Useful for debugging.

Thanks -h

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 7, 2008, 4:30pm UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261/4 "2008-10-07T16:30:31Z")

</div>

Well, I suppose there are incorrectly formatted links too… I was  
talking about correctly formatted links that point to a 400+ status  
code resource. Something libxml would not pick up since I guess you’re  
talking about its syntax checking bit.

Since the entire document is accessible from the Hpricot::Elem it  
seems plausible to count the characters up to and after the element. A  
15min look at the source didn’t reveal anything obvious… Have a nasty  
feeling that this type of thing would have to be done in the compiled  
C section of it…

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 7, 2008, 3:57pm UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261/5 "2008-10-07T15:57:36Z")

</div>

On Oct 7, 3:58 am, “removed\_email\_address@domain.invalid”  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Hi Mark,
> 
> I’m writing a broken link reporting type tool. When I find a dodgy tag  
> I’d like to be able to relay the character position and or line number  
> to the user. Useful for debugging.

So, are you really interested in broken _links_ (as in a GET does not  
return a 200 result code) or broken HTML? I have done the former via  
AJAX (jQuery sends links to a backend rails action, and if it is  
broken changes the class of the link to display a red background). The  
latter may be able to be done with libxml, which reports the character  
position of broken input.

– Mark.

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 7, 2008, 7:40pm UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261/6 "2008-10-07T19:40:41Z")

</div>

On Oct 7, 10:28 am, “removed\_email\_address@domain.invalid”  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Well, I suppose there are incorrectly formatted links too… I was  
> talking about correctly formatted links that point to a 400+ status  
> code resource. Something libxml would not pick up since I guess you’re  
> talking about its syntax checking bit.

Well, libxml stores the line number of every element. So you can  
extract all links, check them, and print out element.line\_num for each  
one that fails the check.

Here’s some starter code:

#----------------------------------------------

require ‘rubygems’  
require ‘xml’

XML::Parser.default\_line\_numbers = true

html = \<\<END\_HTML

 test Here is a [broken link.](http://brok.en) END\_HTML

parser = XML::Parser.string html  
doc = parser.parse

def broken?(link)  
true  
end

doc.find(“//a[@href]”).each do |link|  
if broken?(link)  
puts “Broken link to #{link[‘href’]} on line #{link.line\_num}”  
end  
end

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 8, 2008, 5:00am UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261/7 "2008-10-08T05:00:51Z")

</div>

On Oct 7, 1:36 pm, I wrote:

> Well, libxml stores the line number of every element. So you can  
> extract all links, check them, and print out element.line\_num for each  
> one that fails the check.

Oops, my example mistakenly used the XML parser, so replace that with  
XML::HTMLparser since you are parsing HTML.

– Mark.

---

<div class="post-metadata">

**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\
**Post date:** [October 8, 2008, 9:08pm UTC](https://www.ruby-forum.com/t/hpricot-elem-index-position/150261/8 "2008-10-08T21:08:49Z")

</div>

Thanks for the hint towards to libxml-ruby! I didn’t even know it  
existed. Can’t see anything for character position but very happy  
indeed. Will have a go at implementing it myself when poss…

cheers  
-h