Perl "Premature end of script headers" error

Question

So I'm running a localhost test server with Windows 7 and Xampp. I'm working on a web crawler that will crawl the web, but when I open it up in my browser I get the Premature end of script headers error. I thought I got this from not including "print "Content-Type: text/html\n\n";" which is generally the issue.. but it wasn't.

This is the code I'm using:

#!"\xampp\perl\bin\perl.exe"
print "Content-Type: text/html\n\n";
use strict; 
use warnings;

use LWP::Simple;
use LWP::UserAgent;
use HTTP::Request;
use HTTP::Response;
use HTML::LinkExtor;

open my $file1,"+>>", ("links.txt");
select($file1);  

my @urls = ('http://www.youtube.com/');

my $browser = LWP::UserAgent->new('IE 6');
$browser->timeout(10);


while (@urls) {
  my $url = shift @urls;
  my $request = HTTP::Request->new(GET => $URL);
  my $response = $browser->request($request);

  if ($response->is_error()) {printf "%s\n", $response->status_line;}
  my $contents = $response->content();

  my ($page_parser) = HTML::LinkExtor->new(undef, $url);
  $page_parser->parse($contents)->eof;
  @links = $page_parser->links;

  foreach $link (@links) {
    push @urls, $$link[2];  # Add link to list of urls before printing it
    print "$$link[2]\n";
  }

  sleep 60;
}

You could always try using `use CGI::Carp qw(fatalsToBrowser);` near the top of your script to see what the exact error message is, here. — summea, Apr 01 '12 at 02:20
I added that to the use list and it still gives me the same error. — Noah R, Apr 01 '12 at 02:22
From the [Stack Overflow Perl FAQ](http://stackoverflow.com/questions/tagged/perl?sort=faq): [How can I troubleshoot my Perl CGI script?](http://stackoverflow.com/questions/2165022/how-can-i-troubleshoot-my-perl-cgi-script) — daxim, Apr 01 '12 at 07:39

score 5 · Answer 1 · answered Apr 01 '12 at 05:29

I thought I got this from not including print "Content-Type: text/html\n\n";

Not exactly. You didn't demonstrate that the print got run, and you didn't demonstrate the print got run before other output.

A compile-time error surely happened, in which case the print statement never got executed. Check your web server's error log for the actual error.

score 4 · Answer 2 · edited Apr 02 '12 at 05:21

At first glance, the code you posted above contains several errors which prevent it from being executed: first $URL, @links and $link are not declared (remember that you are under strict). Then another problem is that LWP::UserAgent->new() doesn't accept an odd number of arguments (since it requires an hash).

Since the error you get can just mean that the script stopped before it returned any output to the web server, the reason could be just those errors.

It can be helpful to run your script from the command line first, just to check it returns anything.

UPDATE

Yes, just by correcting the above mentioned errors your script seems to work (on Linux, from the command line). It still produces several warnings (and performs some unnecessary operations), which should be eliminated as well.

Perl "Premature end of script headers" error

2 Answers2