Regex in xml not working as expected

Question

I am novice here and I am trying to search and replace a string in a xml file which is as given below:

<name>xxx.yyy_zzz</name>
      <constructor_arguments />
      <parameters>
        <parameter>
          <name>Name</name>
          <string>
            <value>yyy</value>
          </string>
        </parameter>
        <parameter>
          <name>abc</name>
          <bool>
            <value>false</value>
          </bool>
        </parameter>
        <parameter>
          <name>abcd</name>
          <bool>
            <value>true</value>
          </bool>
        </parameter>
        <parameter>
          <name>aa</name>
          <integer>
            <value>10</value>
          </integer>
        </parameter>
        <parameter>
          <name>bb</name>
          <integer>
            <value>100</value>
          </integer>
        </parameter>
        <parameter>
          <name>runtime_disabled</name>
          <bool>
            <value>false</value>
          </bool>

I have tried the following to change runtime_disabled value to true but it did not happen which I expect to happen, can anyone tell why is it so and provide suitable solution for the same to work

$data=~ s/(xxx\.i\yyy\_zzz\s*?<\/name>(.+?)runtime_disabled\s*?<\/name>\s*?<bool>\s*?<value>\s*?<value>.*?<\/value>)/$1true$2/g;

seems like you are trying to get names so always better to use parser for xml docs try this link stackoverflow.com/questions/2052179/… — Pavneet_Singh
– Pavneet_Singh, Commented Oct 29, 2016 at 16:55

zdim · Accepted Answer · 2022-06-27 20:17:35Z

1

Parsing well-formed XML should practically always be done using modules. Much has been said about that over time, see for example this page and this page, among many others. I also hear that truly bad things may come to pass otherwise.

Here is an example of how to do what you ask using XML::libXML. Another excellent module is XML::Twig. I completed your sample so to make it a well-formed XML file (shown below code).

use strict 'all';
use warnings;

use XML::LibXML;    

my $file = 'file.xml';

my $doc = XML::LibXML->load_xml(location => $file, no_blanks => 1); 

# Form the XPath expression used to find the 'name' nodes
my $xpath = '//doc/constructor_arguments/parameters/parameter/name';

foreach my $node ($doc->findnodes($xpath)) 
{
    # Select the particular 'name' tag that is needed
    if ($node->to_literal eq 'runtime_disabled') 
    {   
        # Query the parent node, for <name>'s sibling <bool>
        foreach my $bval ($node->parentNode->findnodes('./bool/value/text()')) 
        {
            my $content = $bval->toString;
            $content =~ s/false/true/;
            $bval->setData($content);
        }
    }   
}

# Write a new file with the change
$doc->toFile('changed_' . $file, 1);

This is meant to be basic, there are quite a few other ways to do the same.

The posted sample was padded as follows

<doc>
... posted text ...
            </parameter>
        </parameters>
    </constructor_arguments>
</doc>

edited Jun 27, 2022 at 20:17

answered Oct 30, 2016 at 1:03

zdim

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2 Comments

Emman Over a year ago

Since it is a XML file I am moving to the method you are suggesting and the eg., mentioned is found to be working.

zdim Over a year ago

@Emman Great -- parsing XML by hand (regex) leads to no end of trouble. By the time you'd clean up one such file you'll learn how to use a module, and then you are taken care of. With either of the two modules I mention you have full control over everything, while simple things are simple. It is instructive reading some of the posts on this topic. I'll add a few links to them.

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