CODEWITHSUNDEEP
perlxpathxml-parsing
user2786324
user2786324

Reputation: 9

Modifying attribute value of xml tag using perl

I am having a very long xml and I wish to update the attribute value of one of the tag which is very deep nested so don't want to go node by node. Also structure is not same for the intended node always as can be seen below: Input XML is:

<Re>
<Co Class="Parameter" ID="CSCP001" Status="Available">
<FileSpec URL="c://mine/testfiles/wln/c.txt"/>
<CoOp Operation="Tag" SourceCS="RGB" SourceObjects="All">
<FileSpec Resource="SourceProfile" URL="c://mine/testfiles/wln/d.txt"/>
</CoOp>
</Co>
<Ru Class="Parameter" ID="IDR002" PartIDKeys="Run" Status="Available">
<Ru EndOfDocument="true" Pages="0" Run="1" RunTag="First">
<La>
<FileSpec URL="c://mine/testfiles/wln/e.txt"/>
</La>
</Ru>
</Ru>
</Re>

and I wish to have output xml as 

<Re>
<Co Class="Parameter" ID="CSCP001" Status="Available">
<FileSpec URL="d://yours/wln/c.txt"/>
<CoOp Operation="Tag" SourceCS="RGB" SourceObjects="All">
<FileSpec Resource="SourceProfile" URL="d://yours/wln/d.txt"/>
</CoOp>
</Co>
<Ru Class="Parameter" ID="IDR002" PartIDKeys="Run" Status="Available">
<Ru EndOfDocument="true" Pages="0" Run="1" RunTag="First">
<La>
<FileSpec URL="d://yours/wln/e.txt"/>
</La>
</Ru>
</Ru>
</Re>

I tried using xml simple, xmllib but not able to do the required. I am new in perl programming.

use XML::LibXML qw( );
use XML::LibXML;
use Data::Dumper;  

my $xml = "a.txt";
my $xpath_expression = 'FileSpec';

my $parser = XML::LibXML->new();
my $doc = $parser->parse_file($xml) or warn "Could not";

my $parser1 = XML::LibXML::Element->new($xml);


for my $FileSpec1 ($doc->getElementsByTagName('FileSpec')) 
{
print $FileSpec1;
my $xpath = '$FileSpec1/@URL';
my ($attr) = $doc->findnodes($xpath);    
$attr->setValue('dfdsa'); 
my ($URL1) = $FileSpec1->findvalue('@URL');
print $URL1;
}

I tried using $node->setAttribute( $aname, $avalue ); but this is throwing exceptions. Please advice.

Upvotes: 0

Views: 3903

Answers (2)

Birei
Birei

Reputation: 36282

You can try with XML::Twig module. It has the twig_handlers option that selects the tags you want and triggers a handler. The default variable $_ has the element and its method set_att() lets you change its value easily:

#!/usr/bin/env perl

use warnings;
use strict;
use XML::Twig;

my $new_url = q{d://yours/wln/d.txt};

my $twig = XML::Twig->new(
        twig_handlers => {
                'FileSpec' => sub { $_->set_att( 'URL', $new_url ) }
         },
        pretty_print => 'indented',
)->parsefile( shift )->print();

Run it like:

perl script.pl xmlfile

That yields:

<Re>
  <Co Class="Parameter" ID="CSCP001" Status="Available">
    <FileSpec URL="d://yours/wln/d.txt"/>
    <CoOp Operation="Tag" SourceCS="RGB" SourceObjects="All">
      <FileSpec Resource="SourceProfile" URL="d://yours/wln/d.txt"/>
    </CoOp>
  </Co>
  <Ru Class="Parameter" ID="IDR002" PartIDKeys="Run" Status="Available">
    <Ru EndOfDocument="true" Pages="0" Run="1" RunTag="First">
      <La>
        <FileSpec URL="d://yours/wln/d.txt"/>
      </La>
    </Ru>
  </Ru>
</Re>

EDIT: Mirod's version pointed out in comments of a more efficient parsing using twig_roots():

#!/usr/bin/env perl

use warnings;
use strict;
use XML::Twig;

my $new_url = q{d://yours/wln/d.txt};

my $twig = XML::Twig->new(
        twig_roots => {
                'FileSpec' => sub { $_->set_att( 'URL', $new_url ); $_->flush }
        },
        twig_print_outside_roots => 1,
        pretty_print => 'indented',
)->parsefile( shift );

Upvotes: 1

choroba
choroba

Reputation: 242333

Your code is too complicated. You need no parser, no elements, just find the urls and change them:

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

use XML::LibXML;

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

for my $url ($xml->findnodes('//FileSpec/@URL')) {
    my $value = $url->getValue;
    $value =~ s{c://mine/testfiles}{d://yours};
    $url->setValue($value);
}

$xml->toFile('new.xml');

Upvotes: 4

Related Questions