XML::Twig Help

onegative has asked for the wisdom of the Perl Monks concerning the following question:

Good day Monks,

I am really having a hard time understanding the XML::Twig module and how to actually use it. I am hoping someone could give me a jumpstart on how to extract attributes and values from any level of the xml tree. I have fumbled and fumbled with different trival examples found but I can't seem to understand the real logic of what I am reading. I would with all sincerity appreciate any help that could be provided. I think if I could get a working example of code against the small snippet of xml defined below I might actually catch on and understand how to walk down any twig and extract the attrib/values regardless of how deep they go. Please pardon my short-comings with regard to OOP.

Many thanks,
Danny

# XML
<AGENT hostname="viper3">
 <LADDER>
  <ACL>
   <ACCOUNT id="4cf031986c">
    <USERNAME>emcon</USERNAME>
    <HOST>*sppcon*</HOST>
    <PERMISSION>CDOPS</PERMISSION>
   </ACCOUNT>
   <ACCOUNT id="b92794bbd7">
    <USERNAME>cpemcon</USERNAME>
    <HOST>*</HOST>
    <PERMISSION>COPS</PERMISSION>
   </ACCOUNT>
   <ACCOUNT id="8ff0478641">
    <USERNAME>dbemcon</USERNAME>
    <HOST>*</HOST>
    <PERMISSION>COPS</PERMISSION>
   </ACCOUNT>
   <ACCOUNT id="22d2647740">
   <USERNAME>tuxemcon</USERNAME>
    <HOST>*</HOST>
    <PERMISSION>COPS</PERMISSION>
    </ACCOUNT>
  </ACL>
 </LADDER>
</AGENT>
[download]

# script
use strict;
use XML::Twig;

my $file = $ARGV[0];

my $twig = XML::Twig->new();

$twig->parsefile($file);

my $root = $twig->root;

foreach my $acl ($root->children('ACL')){
    print $acl->att('id');
    print "\n";
    print $acl->first_child('USERNAME');
    print "\n";
    print $acl->first_child('HOST');
    print "\n";
    print $acl->first_child('PERMISSION');
    print "\n";
}
[download]

Comment on XML::Twig Help Select or Download Code

Replies are listed 'Best First'.
Re: XML::Twig Help by toolic (Bishop) on Jan 07, 2011 at 14:13 UTC
One approach is to use Twig handlers. For example: use warnings; use strict; use XML::Twig; my $xmlstr = <<EOF; <AGENT hostname="viper3"> <LADDER> <ACL> <ACCOUNT id="4cf031986c"> <USERNAME>emcon</USERNAME> <HOST>sppcon</HOST> <PERMISSION>CDOPS</PERMISSION> </ACCOUNT> <ACCOUNT id="b92794bbd7"> <USERNAME>cpemcon</USERNAME> <HOST></HOST> <PERMISSION>COPS</PERMISSION> </ACCOUNT> <ACCOUNT id="8ff0478641"> <USERNAME>dbemcon</USERNAME> <HOST></HOST> <PERMISSION>COPS</PERMISSION> </ACCOUNT> <ACCOUNT id="22d2647740"> <USERNAME>tuxemcon</USERNAME> <HOST></HOST> <PERMISSION>COPS</PERMISSION> </ACCOUNT> </ACL> </LADDER> </AGENT> EOF my $twig = XML::Twig->new( twig_handlers => {ACCOUNT => \&acct} ); $twig->parse($xmlstr); sub acct { my ($t, $elt) = @_; print $elt->att('id'), "\n"; print $elt->first_child('USERNAME' )->text(), "\n"; print $elt->first_child('HOST' )->text(), "\n"; print $elt->first_child('PERMISSION')->text(), "\n"; print "\n"; } __END__ 4cf031986c emcon sppcon* CDOPS b92794bbd7 cpemcon * COPS 8ff0478641 dbemcon * COPS 22d2647740 tuxemcon * COPS [download] Update: There is a great tutorial at http://web.archive.org/web/20080702002018/http://xmltwig.com (unfortunately, the tutorial link from XML::Twig seems to be down). Update: using mirod's suggestion, and refactoring a little... `sub acct { my ($t, $elt) = @_; print $elt->att('id'), "\n"; for my $tag (qw(USERNAME HOST PERMISSION)) { print $elt->field($tag), "\n"; } print "\n"; }` [download]	[reply] [d/l] [select]
Re^2: XML::Twig Help by mirod (Canon) on Jan 07, 2011 at 14:35 UTC
Usually, instead of writing `$elt->first_child('USERNAME' )->text()`, I write `$elt->field( 'USERNAME')`, it is easier to read. It also doesn't die if there is no USERNAME child, which may be convenient. Oh, and xmltwig.com is down at the moment, but it's mirrored at mirod.org.	[reply] [d/l] [select]
Re^3: XML::Twig Help by toolic (Bishop) on Jan 07, 2011 at 14:42 UTC
++mirod, I was unaware of `field`. On another topic, you probably didn't see my update regarding access to your excellent website. Were you aware that it has been tough to get to for some time now?	[reply] [d/l]
Re^4: XML::Twig Help by onegative (Scribe) on Jan 07, 2011 at 17:08 UTC
Re^5: XML::Twig Help by toolic (Bishop) on Jan 07, 2011 at 17:19 UTC
Re^4: XML::Twig Help by onegative (Scribe) on Jan 10, 2011 at 21:31 UTC
Re^5: XML::Twig Help by toolic (Bishop) on Jan 10, 2011 at 21:46 UTC
Some notes below your chosen depth have not been shown here
Re: XML::Twig Help by Gulliver (Monk) on Jan 07, 2011 at 14:33 UTC
Take a look at the module LibXML. XPath is what I use for grabbing or changing nodes in XML. The LibXML module comes with example scripts using XPath and there are XPath tutorials out there. `#************************************************** # # pass this the xml file name. # uses LibXML and XPath to find the username. # sub connect_check { my ($xml_file) = @_; use XML::LibXML; my $parser = XML::LibXML->new(); my $doc = $parser->parse_file($xml_file); foreach my $element ($doc->findnodes("//USERNAME")) { my $user = $element->to_literal; print "$xml_file,$user,-\n"; } }` [download]	[reply] [d/l]


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