XML::Twig - Using xpath with twig roots

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

I have a xml file like this(pasted only a part of the xml)

<bitrate name="1000">
                        <track type="V">
        
                                <range>
                                        <rangeStartTime>1261287</range
+StartTime>
                                        <rangeEndTime>1324271</rangeEn
+dTime>

                                </range>
                                <range>
                                        <rangeStartTime>1324282</range
+StartTime>
                                        <rangeEndTime>0.000</rangeEndT
+ime>
                                        
                                </range>
                        </track>
                </bitrate>
[download]

I want to extract the value of 1st rangeStartTime

my $twig =  XML::Twig->new(
                        twig_roots => { "bitrate[\@name=\"1000\"]/trac
+k[\@type=\"V\"]/range[1]/rangeStartTime" => \&update,  },
               )
           ->parse($filename);
print $value;
sub update {
    my ($twig, $server) = @_;
        $value= $server->text;
}
[download]

This gives me the 2nd rangeStartTime in the xml.

If i use the xpath like

"bitrate[\@name=\"1000\"]/track[\@type=\"V\"]/range[position() = 1]/ra
+ngeStartTime"
[download]

I get an error

"unrecognized expression in handler: 'bitrate[@name="1000"]/track[@typ
+e="V"]/range[position() = 1]/rangeStartTime' at try16.pl line 35"
[download]

I tried to use findnode() also

my $count = $t->findnodes("bitrate[\@name=\"1000\"]/track[\@type=\"V\"
+]/range[position() = 1]/rangeStartTime");
[download]

It gives error like this

error in xpath expression bitrate[@name="1000"]/track[@type="V"]/range
+[position() = 1]/rangeStartTime at position() = 1 at /usr/share/perl5
+/XML/Twig.pm line 3085
[download]

I have xml::xpath installed on my system
I am stuck on this for quite a while, any help would be appreciated.

Extra code tags added by GrandFather

Comment on XML::Twig - Using xpath with twig roots Select or Download Code

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Re: XML::Twig - Using xpath with twig roots by choroba (Cardinal) on Dec 19, 2011 at 12:47 UTC
As documented, Twig does not support full XPath for handlers. Either create a flag that prevents processing of the 2nd and following occurences, or use a different module to handle XML that supports XPath (as XML::LibXML::Reader). Update :An example using my favourite XML handling module, XML::XSH2: `open 944240.xml ; echo /bitrate[@name="1000"]/track[@type="V"]/range[1]/rangeStartTime ;` [download]	[reply] [d/l]
Re^2: XML::Twig - Using xpath with twig roots by Anonymous Monk on Dec 19, 2011 at 14:38 UTC
Thanks. Does findnodes() also not support the full Xpath? I see references that it does, but somehow it doesnt work for me.	[reply]
Re^3: XML::Twig - Using xpath with twig roots by Khen1950fx (Canon) on Dec 19, 2011 at 23:58 UTC
According to this post, findnodes() uses the full XPath engine. Also, I noticed that the use of position selectors like `range[1]` isn't supported on twig_handlers or twig_roots. Since you're dealing with a very, very small XML, I tried this and returned both rangeStartTimes. I cheated:)... `#!/usr/bin/perl -l use strict; use warnings; use XML::Twig::XPath; $\|=1; my $file = '/root/Desktop/bitrate.xml'; my $twig = XML::Twig::XPath->new( twig_roots => { "//range/rangeStartTime" => \&update }); $twig->parsefile($file); sub update { my ($twig, $server) = @_; print $server->text; }` [download] Here's the tidied XML: `<?xml version="1.0" encoding="UTF-8"?> <bitrate name="1000"> <track type="V"> <range> <rangeStartTime>1261287</rangeStartTime> <rangeEndTime>1324271</rangeEndTime> </range> <range> <rangeStartTime>1324282</rangeStartTime> <rangeEndTime>0.000</rangeEndTime> </range> </track> </bitrate>` [download] Update: fixed typo	[reply] [d/l] [select]