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

Hello,

I've been playing with, and trying to learn, XML::LibXML. I've been trying to get the values from specific nodes based on one of its attributes. I can get and print "all" the node values, and I can get and print just the specific attribute values, but I can't seem to figure out how to print the node values of nodes with specific attributes.

Here is the xml I'm using. I'd like to grab the values from the <Data> nodes, but only the ones with the "name" attribute that equals "NAME_2".

<xml>
<Document>
    <Name>Places To Visit</Name>
    <Folder>
        <Place>
            <Name>Location 1</Name>
            <ExtendedName>
                <Data name="NAME_0">United States</Data>
                <Data name="NAME_1">Utah</Data>
                <Data name="NAME_2">Salt Lake City</Data>
            </ExtendedName>
        </Place>
        <Place>
            <Name>Location 2</Name>
            <ExtendedName>
                <Data name="NAME_0">United States</Data>
                <Data name="NAME_1">Rhode Island</Data>
                <Data name="NAME_2">Providence</Data>
            </ExtendedName>
        </Place>
        <Place>
            <Name>Location 3</Name>
            <ExtendedName>
                <Data name="NAME_0">United States</Data>
                <Data name="NAME_1">Wisconsin</Data>
                <Data name="NAME_2">Green Bay</Data>
            </ExtendedName>
        </Place>
        <Place>
            <Name>Location 4</Name>
            <ExtendedName>
                <Data name="NAME_0">United States</Data>
                <Data name="NAME_1">Wyoming</Data>
                <Data name="NAME_2">Casper</Data>
            </ExtendedName>
        </Place>
    </Folder>
</Document>
</xml>

[download]

Here is the small bit of code that I'm using to pull out the contents of the attributes, but I don't know how to get the node values. I hope that makes sense.

Thank you for your help!

#!/usr/bin/perl

use strict;
use warnings;
use XML::LibXML;

my $xml = XML::LibXML->load_xml(location => 'locations.xml');

foreach my $node2 ($xml->findnodes('//Place')) {
    my $attr;
    foreach( $node2->findnodes('./ExtendedName/Data/@name') ) { 
        $attr = $_->textContent();
        if($attr eq "NAME_2" ) { print $_->textContent() . "\n"; }
    }
}

[download]

Replies are listed 'Best First'.
Re: XML Node Values Based On Attributes
by choroba (Cardinal) on Sep 29, 2022 at 19:22 UTC
    It's much shorter and also faster to do most of the work in XPath. 
    #!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use XML::LibXML;

my $xml = 'XML::LibXML'->load_xml(location => 'file.xml');

for my $place ($xml->findnodes('/xml/Document/Folder/Place')) {
    print $place->findvalue('Name'), "\t";
    my $name2 = $place->findvalue('ExtendedName/Data[@name="NAME_2"]')
+;
    say $name2;
}

    [download]

    If you want to learn XPath, I humbly recommend you XML::XSH2, a module I happen to maintain. It's a wrapper around XML::LibXML which features an interactive shell where you can play with the data and XPath. The above code can be tried like this: 

    $scratch/> open file.xml
parsing file.xml
done.

/> for /xml/Document/Folder/Place echo (Name) ExtendedName/Data[@name=
+"NAME_2"]
Location 1 Salt Lake City
Location 2 Providence
Location 3 Green Bay
Location 4 Casper

    [download]
    map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
[reply]
[d/l]
[select]
      Thank you! I've not looked at XPath directly. I'll have to do that.
[reply]
Re: XML Node Values Based On Attributes
by hippo (Archbishop) on Sep 29, 2022 at 22:13 UTC

    There are so many different ways to approach this given the size of the toolkit that is libxml2. Here is one native approach.

    #!/usr/bin/env perl
use strict;
use warnings;

use XML::LibXML;

my $xml = XML::LibXML->load_xml(location => 'locations.xml');

my $nl = $xml->getElementsByLocalName ('Data');
my @text;

for my $node ($nl->get_nodelist) {
    push @text, $node->textContent if 'NAME_2' eq $node->getAttribute 
+('name');
}

print "$_\n" for @text;

    [download]

    I've structured it this way because to me it is pretty easy to follow and clear what is going on. YMMV.

    🦛

[reply]
[d/l]
      Thank you! Nice and simple, I like it.
[reply]

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