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

I am using XML::Twig with twig_roots in a script to filter out elements and print them to a separate file. The script is using $twig->flush() and $twig->purge() to further filter elements and only print the ones that match certain criteria. I am running into issues where twig_print_outside_roots is adding extra blank lines to the output.

Am I doing something wrong? Is there some option ("replace_flushed_nodes_with_blank_line => 0" perhaps?) that I need to set to disable this? I am still learning how to use XML::Twig, so any critiques, comments, and idiom suggestions would greatly be appreciated!

Thank you for your time.

Sample code and output:

#!/usr/bin/perl
use 5.016;
use strict;
use warnings;
use XML::Twig;

{
    open (my $OFILE, '>:utf8', './bits.xml') or die "Could not open [.
+/bits.xml]:\n$!\n$^E";
    
    my $t = XML::Twig->new(
        twig_roots => {
            'statement' => sub { push @_, $OFILE; &_statement; 1; },
        },
        twig_print_outside_roots => $OFILE,
        pretty_print => 'indented',
    );
    
    $t->parse(*DATA);
    
    close $OFILE;
}

sub _statement {
    my ($_twig, $stmt_element, $OFILE) = @_;
    
    my $acct = $stmt_element->find_nodes('primary/acct', 0)->trimmed_t
+ext();
    
    if ( $acct eq '903264' ) {
        $_twig->flush($OFILE);
    } else {
        $_twig->purge();
    }
    
    return;
}

__DATA__
<batch>
    <header>
        <foo>1</foo>
        <bar>2</bar>
        <baz>3</baz>
    </header>
    <statement>
        <primary>
            <acct>000000</acct>
        </primary>
        <bits>Im an apple!</bits>
    </statement>
    <statement>
        <primary>
            <acct>000000</acct>
        </primary>
        <bits>Im a carrot!</bits>
    </statement>
    <statement> <!-- I only want this statement -->
        <primary>
            <acct>903264</acct>
        </primary>
        <bits>Im a potato!</bits>
    </statement>
    <statement>
        <primary>
            <acct>000000</acct>
        </primary>
        <bits>Im a pear!</bits>
    </statement>
    <statement>
        <primary>
            <acct>000000</acct>
        </primary>
        <bits>Im a pickle!</bits>
    </statement>
    <statement>
        <primary>
            <acct>000000</acct>
        </primary>
        <bits>Im a banana!</bits>
    </statement>
    <statement>
        <primary>
            <acct>000000</acct>
        </primary>
        <bits>Im an eggplant!</bits>
    </statement>
    <trailer>
        <stuff>Oh god how did this get here i am not good with compute
+r!</stuff>
    </trailer>
</batch>

[download]

Output: 

<batch>
    <header>
        <foo>1</foo>
        <bar>2</bar>
        <baz>3</baz>
    </header>
    
    
    
  <statement>
    <!-- I only want this statement -->
    <primary>
      <acct>903264</acct>
    </primary>
    <bits>Im a potato!</bits>
  </statement>
    
    
    
    
    <trailer>
        <stuff>Oh god how did this get here i am not good with compute
+r!</stuff>
    </trailer>
</batch>>

[download]

Expected output: 

<batch>
    <header>
        <foo>1</foo>
        <bar>2</bar>
        <baz>3</baz>
    </header>
  <statement>
    <!-- I only want this statement -->
    <primary>
      <acct>903264</acct>
    </primary>
    <bits>Im a potato!</bits>
  </statement>
    <trailer>
        <stuff>Oh god how did this get here i am not good with compute
+r!</stuff>
    </trailer>
</batch>

[download]

Replies are listed 'Best First'.
Re: XML::Twig's twig_print_outside_roots adds extra blank lines to output
by choroba (Cardinal) on Jun 12, 2014 at 17:12 UTC
    You told XML::Twig to print "outside roots". The whitespace around the statement tags is part of the XML, they are text() nodes, and they get printed as you wanted.
    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]
[d/l]
[select]

      Thanks for the clarification

      Is there a way to filter out that text() whitespace when twig_print_outside_roots is enabled? Or is the better option to use twig_handlers in lieu of twig_roots?

[reply]
[d/l]
[select]
      I'd like to know the answer to this also, please.
[reply]
Re: XML::Twig's twig_print_outside_roots adds extra blank lines to output
by remiah (Hermit) on Jun 27, 2014 at 14:17 UTC

    hello ateague.
    Sometimes I met the case when pretty print doesn't work with XML::Twig. If pretty print is the problem, how about this?

    XML::Twig->new(
    twig_handlers => {
        'statement' => sub {
            my($twig,$elt)=@_;
            if( $elt->find_nodes('primary/acct', 0)->trimmed_text() eq
+ '903264' ){
                $twig->flush;
            }else {
                $twig->purge;
            }
        },
        'statement//*' =>sub {},    #skip descendants of statement
        '_default_' => sub {        #just flush
            my($twig,$elt)=@_;
            $twig->flush;
        }
    },
    #twig_print_outside_roots =>1,
    pretty_print => 'indented',
)->parse(*DATA);

__DATA__
same data

    [download]
    This prints pretty with my XML::Twig 
    C:\temp>perl -MXML::Twig -e "print $XML::Twig::VERSION"
3.42

    [download]
    This example be "potato", becuase it kills the advantage to use twig_root.
    good luck.

[reply]
[d/l]
[select]

      Thank you very much Remiah! That was exactly what I was looking for.

      For those that come after, here is the final code I used to get my desired output:

      Read more... (3 kB)

[reply]
[d/l]

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