Some tips on debugging handlers

[David Coppit]

Here are a few tricks I use to debug handlers that have "gone wrong".
Also be sure to read the handler writer's tutorial at
http://www.newsclipper.com/writinghandlers.htm, and see some tips I
posted at
http://www.mail-archive.com/newsclipperdevlist@newsclipper.com/msg00239.html

1) First, check the output html page for a warning or error emitted by
News Clipper that explains what happened. A lot of times you can
determine which handler messed up this way.

For example, an error like "Handler foo was loaded and executed, but
the acquisition failed" would tell you that the handler couldn't grab
the information from the remote site. This is probably the #1 cause of
handler failures.

2) Use Perl's Data::Dumper module to see exactly what data is being
processed. For example, to see what was grabbed from the remote site,
do this:

  my $data = GetLinks($url,$startpattern,$endpattern);
# Added next two lines. The "die" will cause NC to print the data and
# stop
use Data::Dumper;
die Dumper $data;
  return undef unless defined $data;

In this example, if you find that $data is undefined, this means that
your start and end patterns are probably wrong. If the information
looks okay, move your dump lines further down in the code and see what
it looks like. For example, if you have some processing to remove
images, you might want to dump the data right after that code to make
sure it is working right.

Hope that helps,
David

____________________________________________________________________________
David Coppit <[EMAIL PROTECTED]>        President, Spinnaker Software
http://www.newsclipper.com/ -- Snip and ship dynamic content to your website


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