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

Hello again,

Everyone has been so helpful I thought I would ask one last question regarding XML::Twig.

I'm using the following code 

#!/perl/bin/perl -w

use strict;
use XML::Twig;

my $twig= new XML::Twig;

open( XML_OUT, ">output.xml") or die $!;

$twig->parsefile( "RoamAboutAP_173.253.52.82.xml");
my $root= $twig->root; 
my @ds= $root->children;   

foreach my $attr (@ds) { 

    my $look = $attr->parent('rrd')->text;
    print $look;
    
    my $blg= sprintf( "TESTING PLACEMENT");          
    my $eblg= new XML::Twig::Elt( 'Average', $blg); 
    $eblg->paste( 'first_child', $attr);
}

# $twig->set_pretty_print('indented');
$twig->print( \*XML_OUT);

close XML_OUT;

[download]

My XML file looks like this: 

- <rrd>
  <version>0001</version> 
  <step>300</step> 
- <!--  Seconds 
  --> 
  <lastupdate>1042244888</lastupdate> 
- <!--  2003-01-10 19:28:08 Eastern Standard Time 
  --> 
- <ds>
  <name>ifOutOctets1</name> 
  <type>COUNTER</type> 
  <minimal_heartbeat>600</minimal_heartbeat> 
  <min>NaN</min> 
  <max>NaN</max> 
- <!--  PDP Status 
  --> 
  <last_ds>1636141175</last_ds> 
  <value>6.2416000000e+002</value> 
  <unknown_sec>0</unknown_sec> 
  </ds>
- <!--  Round Robin Archives 
  --> 
- <rra>
  <cf>AVERAGE</cf> 
  <pdp_per_row>1</pdp_per_row> 
- <!--  300 seconds 
  --> 
  <xff>5.0000000000e-001</xff> 
- <cdp_prep>
- <ds>
  <value>NaN</value> 
  <unknown_datapoints>0</unknown_datapoints> 
  </ds>
- <ds>
  <value>NaN</value> 
  <unknown_datapoints>0</unknown_datapoints> 
  </ds>
  </cdp_prep>
- <database>
- <!--  2003-01-08 17:30:00 Eastern Standard Time / 1042065000 
  --> 
- <row>
  <v>NaN</v> 
  <v>NaN</v> 
  <v>NaN</v> 
  <v>NaN</v> 
  </row>
- <!--  2003-01-08 17:35:00 Eastern Standard Time / 1042065300 
  --> 
- <row>
  <v>6.3173066667e+001</v> 
  <v>2.2418133333e+001</v> 
  <v>3.7560151111e+002</v> 
  <v>1.7984751111e+002</v> 
  </row>
- <!--  2003-01-10 19:25:00 Eastern Standard Time / 1042244700 
  --> 
- <row>
  <v>9.5548400000e+001</v> 
  <v>3.1534622222e+001</v> 
  <v>4.0781324444e+002</v> 
  <v>1.9573493333e+002</v> 
  </row>
  </database>
  </rra>
  </rrd>

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What I want to do is search for a specidifc tag, say maybe <ds> or the <v> tag.

I am able to sucessfully look at the root tag, but how can I look at the children of the root node in my foreach loop?

I'll continue reading the perldoc
Thanks!

Replies are listed 'Best First'.
Re: XML Twig parse
by mirod (Canon) on Jan 20, 2003 at 20:39 UTC

    Instead of using $root->children just use $root->children( 'ds') which will give you only the ds children, in the document order.

    All navigation methods (children, first_child, next_sibling, descendants...) accept an extra argument, a condition used to filter results. See the module doc (which I admit is pretty huge and hard to navigate) for more info.

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Re: XML Twig parse
by boo_radley (Parson) on Jan 20, 2003 at 20:41 UTC

    What I want to do is search for a specidifc tag, say maybe <ds> or the <v> tag.
    you can specify search criteria in the call to the children method :
    my @ds= $root->children("ds");# get only ds children
    my @ds= $root->children('ds[@name="foo"]');# get only ds children with a name attribute of foo
    and so on.

    update Damn module authors jumping in :-) Hey mirod, you should expound on conditions in the docs a bit more, a lot of people get tripped up on them.

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      I will write more about conditions once I am happy with them ;--( At the moment they are processed by a very poor regex-based parser. I need to write a real XPath parser, probably using Parse::Yapp. Then the doc will be written... it will be the XPath spec! Except that this will be "navigational XPath", and that I will also have to properly identify the subset of XPath that can be used for twig_roots (all we know about an element is its ancestors, and maybe their attributes) or twig_handlers (we know everything that happened before the end tag of the element),so I know when to refuse an XPath expression if it is in the wrong context.

      As for now, the doc for the development version is now generated through perldoc and is a little better x-linked, so I will add links to the description of the conditions from all navigation functions.

[reply]
        Thanks Mirod

        One last question, what is the syntax to get the children of children?

        I.E. 

        The children of rra and or their children cdp_prep or database

        [download]
        Thanks
[reply]
[d/l]

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