Not an Array reference navigating XML::Simple structure

Question

I am new to Perl. I am trying to loop for each entry in xml file to perform a task but it's dying with "not an array reference at line 9".

My script is

#!/usr/bin/perl
# use module
use XML::Simple;
# create object
$xml = new XML::Simple;
# read XML file
$data = $xml->XMLin("data.xml");
# access XML data
foreach my $entry (@{$data->{entry}}){
print $entry->{'source-translation'}->{'static-ip'}-{'translated-address'};
}

My XML file data is

<?xml version="1.0"?>
<config version="6.0.0" urldb="paloaltonetworks">
  <entry name="DROP NAT">
    <source-translation>
      <static-ip>
        <bi-directional>yes</bi-directional>
        <translated-address>192.91.75.129</translated-address>
      </static-ip>
    </source-translation>
    <to>
      <member>Outside</member>
    </to>
    <from>
      <member>DROP</member>
    </from>
    <source>
      <member>192.91.66.72</member>
    </source>
    <destination>
      <member>any</member>
    </destination>
    <service>any</service>
    <description>NAT for DROP FTP Server</description>
    <to-interface>ethernet1/1</to-interface>
    <nat-type>ipv4</nat-type>
  </entry>
  <entry name="SDROP NAT">
    <source-translation>
      <static-ip>
        <bi-directional>yes</bi-directional>
        <translated-address>192.91.75.154</translated-address>
      </static-ip>
    </source-translation>
    <to>
      <member>Outside</member>
    </to>
    <from>
      <member>DROP</member>
    </from>
    <source>
      <member>192.91.66.79</member>
    </source>
    <destination>
      <member>any</member>
    </destination>
    <service>any</service>
    <description>NAT for SFTP server SDROP</description>
    <to-interface>ethernet1/1</to-interface>
    <nat-type>ipv4</nat-type>
  </entry>
</config>

I want to list translated-address in each entry. Assume there are lot of entries like this. Please help me.

Note: there is a minus sign in front of `'translated-address'` probably you meant `->`? — Håkon Hægland, Dec 16 '15 at 10:57

score 1 · Answer 1 · edited May 23 '17 at 10:27

The default value for the KeyAttr option is

KeyAttr => [qw( name key id )]

That means that XML::Simple will convert

 [ { name => $name1, ... }, { name => $name2, ... }, ... ]

into

 { $name1 => { ... }, $name2 => { ... }, ... }

You could use the following option to the get the structure you expect.

KeyAttr => []

Don't forget to also provide the following option if you want your code to work when only one entry is present:

ForceArray => [qw( entry )]

The use of XML::Simple is discouraged, even by its own documentation.

XML::LibXML solution:

use XML::LibXML qw( );
my $parser = XML::LibXML->new();
my $doc = $parser->parse_file('data.xml');
for my $node ($doc->findnodes(
   '/config/entry/source-translation/static-ip/translated-address'
)) {
   print($node->textContent(), "\n");
}

score 0 · Answer 2 · answered Dec 16 '15 at 11:10

As you stated $data->{entry} is not an array reference in your data structure; it is a hash reference.

Check the script below, it accesses the data in the hash:

#!/usr/bin/perl
use v5.10; use strict; use warnings;
use XML::Simple;

my $xml = new XML::Simple;
my $data = $xml->XMLin("data.xml");
for my $entry (keys %{$data->{entry}}){
  say $data->{entry}->{$entry}->{'source-translation'}->{'static-ip'}->{'translated-address'};
}

And as Сухой27 pointed out; if you'd use Data::Dumper you'd be able to see the data structure and you'd see the hash instead of your assumed array.

score 0 · Answer 3 · edited Dec 17 '15 at 03:36

Here is your problem:

use XML::Simple;

XML::Simple misleads you. It isn't simple at all. Unless you have absolutely no choice (and you probably do - it isn't core) then using another parser gives less pain.

Like:

use XML::Twig;
print $_ -> trimmed_text,"\n" for  XML::Twig -> new -> parsefile ( 'data.xml') -> get_xpath ( '//translated-address');

expanded out that's more like:

use strict ;
use warnings;
my $twig = XML::Twig -> new;
$twig -> parsefile ( 'data.xml');
foreach my $entry ( $twig -> findnodes ('//entry'))  {
    print $entry -> first_child('source-translation') -> first_child('static-ip') -> first_child_text('translated-address');
}

Not an Array reference navigating XML::Simple structure

3 Answers3