Question

I’m using PDF::FromHTML to generate a PDF from HTML(as the name of the module would imply) 🙂

I’m able to run it from the command line fine and receive my expected output – however when I use the exact same code in my web app, the output doesn’t look correct at all – text is appearing in the wrong places and not all of it is appearing.

I am using the exact same input file in the web app and on the command line – some reason when it’s called from inside my web app, it’s appearing differently.

Here is the code:

use PDF::FromHTML;  my $filename = '/tmp/backup.html';   my $font      = 'Helvetica'; my $encoding  = 'utf-8'; my $size      = 12; my $landscape = 0;  my $pdf = PDF::FromHTML->new(  encoding => $encoding, );   my $input_file = $filename; my $output_file = '$input_file.pdf';   warn '$input_file\n$output_file\n'; $pdf->load_file($input_file); $pdf->convert(   Font        => $font,   LineHeight  => $size,   Landscape   => $landscape, );  $pdf->write_file($output_file); 

The web app code is the same, just with that block thrown into a method.

I have looked at the two generated PDF files in a hex editor and found the differences. They’re the same until a block whose intent I can’t understand…

Good PDF contents at that block:

/Length 302 >> stream **binary data endstream endobj 10 0 obj << /Filter [ /FlateDecode ] /Length 966 

Bad PDF contents:

/Length 306 >> stream **binary data endstream endobj 10 0 obj << /Filter [ /FlateDecode ] /Length 559 

As you can see, the length of the content contained in here differs, as does the binary data contained in that stream(the length 302 vs length 306 one) as well as the next stream(the length 966 vs 559 one).

I’m not entirely sure what could be causing this discrepancy, the only thing I can think of is some sort of difference in the environments when I’m running this as my user on the command line versus running it from the web app. I don’t know where I should start with debugging that, however.

Answer 1

In general, the CGI environment is different than your interactive login environment just like someone else’s login environment is different than yours. The trick is to figure out what thing you have set or unset on your command line that makes your program work.

You might want to see my Troubleshooting Perl CGI scripts for a step-by-step method to track down these problems.

Some things to investigate:

• Is your CGI script running on the same platform (i.e. is it a Windows versus Unix sorta thing)
• What’s different about the environment variables?
• Does your CGI script use the same version of Perl?
• Does that perl binary have different compilation options?
• Are you using the same versions of the modules?
• If some of those modules use external libraries, are they the same?

A useful technique is to make your login shell temporarily have the same setup as your CGI environment. Once you do that, you should get the same results on the command line even if those results are wrong. However, once you get the wrong results you can start tracking it down from the command line.

Good luck.