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

I am trying to filter through a large XML file, pull out the elements I need within the value range restricted by the IF statement, and export them to CSV. However, I am a newb to programming and this is my first exposure to Perl, so I get syntax errors on lines 14 and 15 and probably doing other things wrong too. Please help me straighten this out!

Here's my code:

#! /usr/bin/perl -w

use strict;
use XML::Twig;

my $twig= new XML::Twig(
  TwigHandlers => {town => \&town}
  );
if( my $file= $ARGV[0]) {$twig->parsefile( 'datafile_towns.xml');
$twig->flush;}

sub town {
  my ($twig, $town) = @_;
  if (my $townx($town->first_child('location')->first_child('mapx'))>5
+00){
    print $town->first_child('towndata')->first_child_text('townname')
+,
          ',', $town->first_child('player')->first_child_text('allianc
+eticker'),
          ',', $town->first_child('player')->first_child_text('playern
+ame'),
          ',', $town->first_child('towndata')->first_child_text('townn
+ame'),
          ',', $town->first_child('location')->first_child_text('mapy'
+),
          ',', $town->first_child_text('location')->first_child_text('
+mapx'),
          print "\n";
    };
    
  $twig->flush;
}

[download]

And here's a snippet of XML:

<towns>
  <server>
    <name>servername</name>
    <servername>servername</servername>
  </server>
  <town>
    <location>
      <mapx>383</mapx>
      <mapy>-1815</mapy>
      <terraintype id="9">terraintype</terraintype>
      <terrainoveralltype id="4">terraintype</terrainoveralltype>
    </location>
    <player>
      <playername id="1">somedude</playername>
      <playerrace>Human</playerrace>
        <playeralliance>
          <alliancename id="18">somealliance</alliancename>
          <allianceticker>AL</allianceticker>
          <alliancetaxrate>0.01</alliancetaxrate>
        </playeralliance>
    </player>
    <towndata>
      <townname id="1">sometown</townname>
      <foundeddatetime>date</foundeddatetime>
      <population>1</population>
      <iscapitalcity>1</iscapitalcity>
      <isalliancecapitalcity>1</isalliancecapitalcity>
    </towndata>
  </town>

[download]

Replies are listed 'Best First'.
Re: TWIGging XML to CSV: what's wrong with my syntax?
by choroba (Cardinal) on Apr 10, 2015 at 21:07 UTC
    Using XML::XSH2, a wrapper around XML::LibXML: 
    stream :f datafile_towns.xml :F /dev/null select town {
    if (location/mapx > 500) {
        echo :n :s (towndata/townname) , (player/playeralliance/allian
+ceticker) ;
        echo :n :s , (player/playername) , (towndata/townname) , (loca
+tion/mapy) ;
        echo :s , (location/mapx);
        rm . ;
    }
}

    [download]

    On MSwin, replace /dev/null with NUL.

    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]
[d/l]
Re: TWIGging XML to CSV: what's wrong with my syntax?
by toolic (Bishop) on Apr 10, 2015 at 20:44 UTC
    This gets past the syntax errors: 
    use warnings;
use strict;
use XML::Twig;

my $twig = XML::Twig->new(
    twig_handlers => { town => \&town },
);
$twig->parsefile('datafile_towns.xml');

sub town {
    my ($twig, $town) = @_;
    if ($town->first_child('location')->first_child_text('mapx') > 300
+) {
        print $town->first_child('towndata')->first_child_text('townna
+me');
        print "\n";
    }
}

__END__

sometown

    [download]

    Key points:

    • "twig_handlers"
    • No "my $townx" and extra parens
    • Need closing "towns" in your snippet
    • I changed 500 to 300 just to see output
[reply]
[d/l]

      Thanks toolic! I went with your modification and extended it a bit to include a couple more conditions.

       
use warnings;
use strict;
use XML::Twig;
my $source_file = 'datafile_towns.xml';
my $out_file = 'illytowns.xml';
my $twig = XML::Twig->new(
    twig_handlers => { town => \&town },
);

$twig->parsefile($source_file);
open (my $fh_out, '>', $out_file) or die "unable to open '$out_file' f
+or writing: $!";

sub town {
    my ($twig, $town) = @_;
    my $townx = $town->first_child('location')->first_child('mapx')->t
+ext;
    my $towny = $town->first_child('location')->first_child('mapy')->t
+ext;
    if (($townx > 556) and ($towny > -2502) and ($towny < -2214)) {
        print $town->first_child('towndata')->first_child_text('townna
+me');
        print "\n";
    }
    
    $twig->print($fh_out);
    $twig->purge;
}

      [download]
      I've added a file handle to print the data to a file rather than to STOUT; however, it is not working correctly, as instead of getting a file with a list of town names I get a a full set of tags for 1 XML element (probably the last element in the XML file). The STDOUT generated by the print statement inside the twig is correct.
[reply]
[d/l]
Re: TWIGging XML to CSV: what's wrong with my syntax?
by runrig (Abbot) on Apr 10, 2015 at 21:24 UTC
    And yet another way, using XML::Rules:
    use warnings;
use strict;

use XML::Rules;

my @attribs = qw(
  townname
  allianceticker
  playername
  townname
  mapy
  mapx
);

my @rules = (
  town => sub {
    my $town = $_[1];
    return if $town->{mapx} <= 500;
    print join(",", @$town{@attribs}), "\n";
    return;
  },
  'player,towndata,location,playeralliance' => 'pass no content',
  _default => 'content',
);
my $xr = XML::Rules->new( rules => \@rules );
$xr->parsefile('tmp.xml');

    [download]
[reply]
[d/l]

      Thanks Runrig! This looks very nice. I've installed XML::Rules and tried running this code but I get an error:

      no element found at line 1, column 0, byte 0 at /usr/local/share/perl/5.18.2/XML/Rules.pm line 745.
[reply]
[d/l]
        That sounds more like your XML file is invalid...did you use my hard-coded filename above instead of your actual file name?
[reply]

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