Scrapper outputing error -w

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

I am creating a scrapper that gets the url from an index and writes it to a dat file. Then another scrapper that reads the dat in a while loop and scrapes data from it. I have two different version of code one that works and one that doesn't. The one that works, I have defined the content in which to scrape. The one that doesn't work, the content is defined in a variable which is read from the dat file. If anyone can help, it would be much appretiated.
Works:


#!/usr/bin/perl
use LWP::Simple;
use HTML::TokeParser;
use URI::Escape;

&sw;

sub sw {
        $content = get('http://example.com/test.html');

....truncated
[download]

Doesn't work:

#!/usr/bin/perl -w
use LWP::Simple;
use HTML::TokeParser;
use URI::Escape;
use DBI;
use DBD::mysql;



$database = "Assets2";
$host = "localhost";
$port = "3306";
$user= "assets";
$password= "xxx";

$dsn = "DBI:mysql:$database:$host:$port";
$connect = DBI->connect($dsn,$user, $password);

&get_index;

sub get_index {
        $query1 = "Select * from devices";
        $query_handle1 = $connect->prepare($query1);
        $query_handle1->execute;
        $query_handle1->bind_columns(\$id,\$device);
        while ($query_handle1->fetch) {
                print "id: $id\tname: $device\n";
                &switch_properties;
        }
}

sub switch_properties {
        $content = get('http://example.com/$device');

...truncated
[download]

Error:

Use of uninitialized value in substr at /usr/lib/perl5/HTML/PullParser
+.pm line 80.
Use of uninitialized value in length at /usr/lib/perl5/HTML/PullParser
+.pm line 83.
[download]

Error with debugger:

Use of uninitialized value in substr at /usr/lib/perl5/HTML/PullParser
+.pm line 80.
 at /usr/lib/perl5/HTML/PullParser.pm line 80
        HTML::PullParser::get_token('HTML::TokeParser=HASH(0x9ce9fd0)'
+) called at /usr/lib/perl5/HTML/TokeParser.pm line 52
        HTML::TokeParser::get_tag('HTML::TokeParser=HASH(0x9ce9fd0)', 
+'tr') called at switchmapHTMLTEST1.pl line 51
        main::switch_properties called at switchmapHTMLTEST1.pl line 2
+8
        main::get_index called at switchmapHTMLTEST1.pl line 19
Use of uninitialized value in length at /usr/lib/perl5/HTML/PullParser
+.pm line 83.
 at /usr/lib/perl5/HTML/PullParser.pm line 83
        HTML::PullParser::get_token('HTML::TokeParser=HASH(0x9ce9fd0)'
+) called at /usr/lib/perl5/HTML/TokeParser.pm line 52
        HTML::TokeParser::get_tag('HTML::TokeParser=HASH(0x9ce9fd0)', 
+'tr') called at switchmapHTMLTEST1.pl line 51
        main::switch_properties called at switchmapHTMLTEST1.pl line 2
+8
        main::get_index called at switchmapHTMLTEST1.pl line 19
[download]

Comment on Scrapper outputing error -w Select or Download Code

Replies are listed 'Best First'.
Re: Scrapper outputing error -w by Corion (Patriarch) on Apr 11, 2011 at 13:48 UTC
It would seem to me that the difference is that `$content = get('http://example.com/$device');` [download] fails (or rather, returns `undef`) while `$content = get('http://example.com/test.html');` [download] works. Maybe consider looking closer into what you actually get, and what is in `$device` and whether the request works from elsewhere.	[reply] [d/l] [select]
Re^2: Scrapper outputing error -w by parkprimus (Sexton) on Apr 11, 2011 at 13:54 UTC
I definitely considered that and would only turn the perlmonks when all else fails. The output of $devices is as expected, I threw in a print statement to verify.	[reply]
Re^3: Scrapper outputing error -w by Corion (Patriarch) on Apr 11, 2011 at 13:57 UTC
You don't show us at all what path your data takes from `get(...)` until it gets to `HTML::PullParser`, where you get a warning (or two). What steps have you taken to confirm that you get the data you expect, and that you pass on the proper data down to HTML::PullParser in both cases? Please help us to help you better by posting a self-contained small program that exhibits the same failure. That way, we can more easily replicate your situation instead of taking guesses.	[reply] [d/l] [select]
Re: Scrapper outputing error -w by chromatic (Archbishop) on Apr 11, 2011 at 18:28 UTC
`$content = get('http://example.com/$device');` If you want to interpolate the contents of `$device`, you need double quotes.	[reply] [d/l] [select]
Re: Scrapper outputing error -w by InfiniteSilence (Curate) on Apr 11, 2011 at 17:44 UTC
If you can, get out of the habit of relying on global variables in functions like that. It is a sure fire way to get confused about what is happening in your code. In the debugger enter a session on your script and immediately do this: `b switch_properties r` [download] When you get into the switch properties code step down until you hit the offending 'get' line and then do this: `p $device` [download] What do you see? Celebrate Intellectual Diversity	[reply] [d/l] [select]