comment on

Hi monks. I had a question here a while back about parsing some XML and I think I'll go with XML::LibXML because it's nice and fast.

However, I'm have a bit of trouble understanding the interface and can't find a nice tutorial to go through

I've got some XML code that looks like this:

<?xml version="1.0" standalone="yes" ?>

<SymCLI_ML>
  <Symmetrix>
    <Symm_Info>
      <symid>000290101935</symid>
    </Symm_Info>
    <Device>
      <Dev_Info>
        <pd_name>Not Visible</pd_name>
        <dev_name>0040</dev_name>
        <configuration>RAID-5</configuration>
        <attached_bcv>N/A</attached_bcv>
        <emulation>CKD-3390</emulation>
        <status>Ready</status>
        <sa_status>N/A</sa_status>
        <service_state>Normal</service_state>
        <ssid>0xD800</ssid>
        <cuimage>0x00</cuimage>
      </Dev_Info>
      <Attached>
        <BCV>N/A</BCV>
        <VDEV>N/A</VDEV>
      </Attached>
      <Product>
        <vendor>
        </vendor>
        <name>
        </name>
        <revision>
        </revision>
        <serial_id>N/A</serial_id>
        <symid>000290101935</symid>
      </Product>
      <Label>
        <type>N/A</type>
        <defined_label>N/A</defined_label>
      </Label>
      <Flags>
        <ckd>True</ckd>
        <worm_enabled>False</worm_enabled>
        <worm_protected>False</worm_protected>
        <dynamic_spare_invoked>False</dynamic_spare_invoked>
        <dynamic_rdf_capability>None</dynamic_rdf_capability>
        <star_mode>False</star_mode>
        <star_recovery_capability>None</star_recovery_capability>
        <star_recovery_state>N/A</star_recovery_state>
        <radiant_managed>False</radiant_managed>
        <restricted_access_dev>False</restricted_access_dev>
        <rdb_checksum_enabled>False</rdb_checksum_enabled>
        <non_exclusive_access>False</non_exclusive_access>
        <scsi3_persist_res>Disabled</scsi3_persist_res>
        <vcm>False</vcm>
        <symmetrix_filesystem>False</symmetrix_filesystem>
        <snap_save_device>False</snap_save_device>
        <gatekeeper>False</gatekeeper>
        <meta>None</meta>
      </Flags>
      <Capacity>
        <block_size>56664</block_size>
        <cylinders>1113</cylinders>
        <tracks>16695</tracks>
        <blocks>16695</blocks>
        <megabytes>902</megabytes>
        <kilobytes>923833</kilobytes>
      </Capacity>
      <Front_End>
        <Port>
          <pd_name>Not Visible</pd_name>
          <director>03A</director>
          <director_type>FICON</director_type>
          <powerpath_type>N/A</powerpath_type>
          <port>0</port>
          <port_status>N/A</port_status>
          <tid>0</tid>
          <lun>0</lun>
          <host_lun>N/A</host_lun>
          <base_address>0</base_address>
          <alias_count>0</alias_count>
        </Port>
        <Port>
          <pd_name>Not Visible</pd_name>
          <director>04A</director>
          <director_type>FICON</director_type>
          <powerpath_type>N/A</powerpath_type>
          <port>0</port>
          <port_status>N/A</port_status>
          <tid>0</tid>
          <lun>0</lun>
          <host_lun>N/A</host_lun>
          <base_address>0</base_address>
          <alias_count>0</alias_count>
        </Port>
        <Port>
          <pd_name>Not Visible</pd_name>
          <director>13A</director>
          <director_type>FICON</director_type>
          <powerpath_type>N/A</powerpath_type>
          <port>0</port>
          <port_status>N/A</port_status>
          <tid>0</tid>
          <lun>0</lun>
          <host_lun>N/A</host_lun>
          <base_address>0</base_address>
          <alias_count>0</alias_count>
        </Port>
        <Port>
          <pd_name>Not Visible</pd_name>
          <director>14A</director>
          <director_type>FICON</director_type>
          <powerpath_type>N/A</powerpath_type>
          <port>0</port>
          <port_status>N/A</port_status>
          <tid>0</tid>
          <lun>0</lun>
          <host_lun>N/A</host_lun>
          <base_address>0</base_address>
          <alias_count>0</alias_count>
        </Port>
      </Front_End>
      <Mirror_Set>
        <Mirror>
          <number>1</number>
          <type>RAID-5</type>
          <status>Ready</status>
          <invalid_tracks>0</invalid_tracks>
        </Mirror>
        <Mirror>
          <number>2</number>
          <type>RAID-5</type>
          <status>Ready</status>
          <invalid_tracks>0</invalid_tracks>
        </Mirror>
        <Mirror>
          <number>3</number>
          <type>N/A</type>
          <status>N/A</status>
          <invalid_tracks>0</invalid_tracks>
        </Mirror>
        <Mirror>
          <number>4</number>
          <type>N/A</type>
          <status>N/A</status>
          <invalid_tracks>0</invalid_tracks>
        </Mirror>
      </Mirror_Set>
      <Back_End>
        <Hyper>
          <type>RAID-5</type>
          <status>Ready</status>
          <number>N/A</number>
          <Disk>
            <director>N/A</director>
            <interface>N/A</interface>
            <tid>N/A</tid>
            <volume_number>N/A</volume_number>
          </Disk>
        </Hyper>
        <Hyper>
          <type>RAID-5</type>
          <status>Ready</status>
          <number>N/A</number>
          <Disk>
            <director>N/A</director>
            <interface>N/A</interface>
            <tid>N/A</tid>
            <volume_number>N/A</volume_number>
          </Disk>
        </Hyper>
      </Back_End>
      <RAID-5_Device>
        <RAID5_Dev_Info>
          <tracks_per_stripe>4</tracks_per_stripe>
          <ready_state>ReadyNoOtherMirror</ready_state>
          <writeprotect_state>EnabledNoOtherMirror</writeprotect_state
+>
          <member_num_of_failing_dev>None</member_num_of_failing_dev>
          <member_which_invoked_spare>None</member_which_invoked_spare
+>
          <disk_director_num_which_owns_spare>-1</disk_director_num_wh
+ich_owns_spare>
          <disk_director_ident_which_owns_spare>N/A</disk_director_ide
+nt_which_owns_spare
        >
          <copy_direction>N/A</copy_direction>
        </RAID5_Dev_Info>
        <Hyper>
          <director>01A</director>
          <interface>D</interface>
          <tid>5</tid>
          <da_vol_num>444</da_vol_num>
          <hyper_num>56</hyper_num>
          <hyper_capacity_in_mb>307</hyper_capacity_in_mb>
          <member_num>4</member_num>
          <member_status>RW</member_status>
          <spare_status>N/A</spare_status>
          <disk_group_num>2</disk_group_num>
          <disk_capacity_in_mb>140014</disk_capacity_in_mb>
        </Hyper>
        <Hyper>
          <director>15A</director>
          <interface>D</interface>
          <tid>5</tid>
          <da_vol_num>468</da_vol_num>
          <hyper_num>56</hyper_num>
          <hyper_capacity_in_mb>307</hyper_capacity_in_mb>
          <member_num>1</member_num>
          <member_status>RW</member_status>
          <spare_status>N/A</spare_status>
          <disk_group_num>2</disk_group_num>
          <disk_capacity_in_mb>140014</disk_capacity_in_mb>
        </Hyper>
        <Hyper>
          <director>02C</director>
          <interface>C</interface>
          <tid>5</tid>
          <da_vol_num>66</da_vol_num>
          <hyper_num>56</hyper_num>
          <hyper_capacity_in_mb>307</hyper_capacity_in_mb>
          <member_num>3</member_num>
          <member_status>RW</member_status>
          <spare_status>N/A</spare_status>
          <disk_group_num>2</disk_group_num>
          <disk_capacity_in_mb>140014</disk_capacity_in_mb>
        </Hyper>
        <Hyper>
          <director>16C</director>
          <interface>C</interface>
          <tid>5</tid>
          <da_vol_num>66</da_vol_num>
          <hyper_num>56</hyper_num>
          <hyper_capacity_in_mb>307</hyper_capacity_in_mb>
          <member_num>2</member_num>
          <member_status>RW</member_status>
          <spare_status>N/A</spare_status>
          <disk_group_num>2</disk_group_num>
          <disk_capacity_in_mb>140014</disk_capacity_in_mb>
        </Hyper>
      </RAID-5_Device>
    </Device>
[download]

The Device tag repeats over 4000 times in this file. I want to extract certain fields out of the XML and build a simple file, one line per device.

I've tried different methods of processing this tree but I think I'm just missing the point somewhere. Here are some examples I've written but I'm not sure I'm on the right track,

my $parser = new XML::LibXML;

my $tree = $parser->parse_file('935.xml');
my $root = $tree->getDocumentElement;

my @devices = $root->findnodes('/SymCLI_ML/Symmetrix/Device/Dev_Info')
+;

for my $device_id ( @devices ) {
    my $dev_name = $device_id->findnodes('./Dev_Name');
    my $dev_conf = $device_id->findnodes('./configuration');
    print $dev_name->to_literal, "\t", $dev_conf->to_literal, "\n";
}
[download]

but this is very slow.

So I tried a different approach, using the getChildrenByTagName method, which works a lot faster

my $parser = new XML::LibXML;

my $tree = $parser->parse_file('935.xml');
my $root = $tree->getDocumentElement;
my @symm_tree    = $root->getChildrenByTagName('Symmetrix') or croak;
for my $symm_tree ( @symm_tree ) {
    my @devices_tree = $symm_tree->getChildrenByTagName('Device') or c
+roak;

    my $device_num;
    for my $device_tree ( @devices_tree ) {
        $device_num++;
        my @devinfo_tree    = $device_tree->getChildrenByTagName('Dev_
+Info') or croak;
        my @capacity_tree      = $device_tree->getChildrenByTagName('C
+apacity') or croak;

        my $dev_name; # key

        for my $devinfo_tree ( @devinfo_tree ) {
            $dev_name = $devinfo_tree->getChildrenByTagName('dev_name'
+);
            my $dev_cnfg = $devinfo_tree->getChildrenByTagName('config
+uration');

            $conf_of{$dev_name} .= $dev_cnfg;
        }

        for my $capacity_tree ( @capacity_tree ) {
            my $cyls = $capacity_tree->getChildrenByTagName('cylinders
+');
            $conf_of{$dev_name} .= $cyls;
        }
    }
}
[download]

Am I getting close to how the module should be used? I'm not sure why method 1 is so slow, as it seems XPath-style statements could be very useful.

I actually need to extract about 30 fields from the XML so I'm concerned that method 2is not necessarily scalable to that sort of usage, and would very much appreciate any feedback!

Thanks for reading this far

~ Michael

In reply to Any help available for a newbie to XML::LibXML? by wardy3

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		`&`
	<		`<`
	>		`>`
	[		`[`
	]		`]`

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.