Grepping data from an html file gives some random value - html

Question

I have a XML file using which I am grepping some of the value based on some regex.
The XML file looks like this-
<Instance>Fuse_Name</Instance>
<Id>8'hed</ID>
<SomeAddr>17'h00baf</SomeAddr>
<PSomeAddr>17'h00baf</PSomeAddr>
I want to retrieve 17'h00baf value from "SomeAddr" tag. I am matching the regex "SomeAddr" so as to reach that row in the file and then using index and substr function I am retrieving value using below code
my $i = index($row,">");
my $j = index($row,"<");
$Size_in_bits = substr $row,$i+1,$j-$i-3;
But after doing this I am not getting 17'h00baf . Instead I am getting 17'h01191 . On similar approach I am able to grep other values which are decimal or string,Only with the hexadecimal values I am facing this problem. Can somebody please tell me what is wrong in the approach??

Answer 1

Please don't parse XML with regexes. Use a proper XML parser.
But, ignoring that advice temporarily, I don't get the behaviour you describe when testing your code.
#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
while (<DATA>) {
next unless /<SomeAddr>/;
my $i = index($_, ">");
my $j = index($_, "<");
my $Size_in_bits = substr $_, $i + 1, $j - $i - 3;
say $Size_in_bits;
}
__END__
<Instance>Fuse_Name</Instance>
<Id>8'hed</ID>
<SomeAddr>17'h00baf</SomeAddr>
<PSomeAddr>17'h00baf</PSomeAddr>
And running it:
$ perl parsexml
17'h00baf
Of course, I've had to guess at what a lot of your code looks like because you didn't give us a complete example to test. So it looks likely that your problems are in bits of the code that you haven't shown us.
(My guess would be that there's another <SomeAddr> tag in the file somewhere.)

Answer 2

Never, ever use a regex to parse HTML/XML/.... Always use a proper parser and then implement your algorithm in the DOM domain.
My solution shows how to parse the XML and then extract the text content from <SomeAddr> nodes at the top-level of the XML document.
#!/usr/bin/perl
use warnings;
use strict;
use XML::LibXML;
my $doc = XML::LibXML->load_xml(IO => \*DATA);
my $xpc = XML::LibXML::XPathContext->new();
# register default NS
$xpc->registerNs('default', 'http://some.domain.com/some/path/to');
foreach my $node ($xpc->findnodes('//default:SomeAddr', $doc)) {
print $node->textContent, "\n";
}
exit 0;
__DATA__
<Root xmlns="http://some.domain.com/some/path/to">
<Instance>Fuse_Name</Instance>
<Id>8'hed</Id>
<SomeAddr>17'h00baf</SomeAddr>
<PSomeAddr>17'h00baf</PSomeAddr>
</Root>
Test run
$ perl dummy.pl
17'h00baf