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

I'm trying to write a perl script to strip tables from html files. There are many tables and some are nested, and I can't figure out how to write the regexp. Can anyone help this regexp newbie. Thanks. Daniel.

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Re: regexp for stripping tables
by zby (Vicar) on Sep 09, 2003 at 08:56 UTC
Re: regexp for stripping tables
by tachyon (Chancellor) on Sep 09, 2003 at 13:17 UTC

    Don't try and do it with a regex. Nested structures are very hard to do with REs. Nested HTML is probably as hard as it gets. Here is how to do it right using HTML::Parser. Yes the Version 2 API takes a little getting used to but is very easy to use once you get your head around it. All we do is increment a counter when we find a opening table tag and decrement it when we find a closing tag. If we have a value > 0 in the counter we are in a table so don't add the original text to our data. If we have a value of 0 we are outside of the tables so add the origtext.

    { package MyParser; use base 'HTML::Parser'; sub start { my($self, $tagname, $attr, $attrseq, $origtext) = @_; $self->{table}++ if $tagname eq 'table'; $self->{data} .= $origtext unless $self->{table}; } sub end { my($self, $tagname, $origtext) = @_; $self->{data} .= "</$tagname>" unless $self->{table}; $self->{table}-- if $tagname eq 'table'; } sub text { my($self, $origtext, $is_cdata) = @_; $self->{data} .= $origtext unless $self->{table}; } sub comment { my($self, $origtext ) = @_; #$self->{data} .= $origtext if $want_comments } } my $p = MyParser->new; $p->parse_file(*DATA); $data = $p->{data}; print $data; __DATA__ <html> <head> <title></title> </head> <body> <p>Hello <tablE> ..... </taBle> <p>World <table> <tr><TABLE> Nested <table> Nested some more </table> </table> </tr> </table > <p>REs can be useful, but HTML parser rocks! </body> </html>

    cheers

    tachyon

    s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

      Dear tachyon,

      Your posting was extremely helpful. I was able to plug your example into my program, and my problem went away. Without your example I would have been quite lost, since I have thus far avoided perl oop and event based parsers. So, in addition to fixing my small problem, I also got a little tutorial on oop and event-based parsing. Capital.

      Thank you,

      Daniel

Re: regexp for stripping tables
by seattlejohn (Deacon) on Sep 09, 2003 at 18:07 UTC
    HTML::TableExtract subclasses HTML::Parser and provides pretty rich mechanisms for getting whatever information you may want.

            $perlmonks{seattlejohn} = 'John Clyman';

Re: regexp for stripping tables
by Anonymous Monk on Sep 09, 2003 at 23:56 UTC
    Thank you all very much for your excellent suggestions, and for helping me solve my tables problem. Once again I am indebted to the perlmonks community.

    Daniel.