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Download files with CGI::Application
Download files with CGI::Application
This tutorial is about how to download files (not necessarily accesible directly from the web server's document path) with CGI::Application.
(First read the CGI::Application tutorial if you don't know how the module works.)
Basically there are six things you have to do to download a file:
  1. Open a file (the user running the web server must have read access to the file).
  2. Read the file contents into a variable.
  3. Close the file.
  4. Get the file size.
  5. Set the HTTP headers properly.
  6. Send the variable contents to the browser.
1. Open the file:
my $downloadfile = $query->param('downloadfile');
my $fullpathdownloadfile = "$fullpath/$downloadfile";
my $output = '';
my $buffer = '';
open my $fh, '<', $fullpathdownloadfile
  or return error_handler("Error: Failed to download file <b>$downloadfile</b>:<br>$!<br>");
2. Read the file contents into a variable:
while (my $bytesread = read($fh, $buffer, 1024)) {
  $output .= $buffer;
}
3. Close the file:
close $fh
  or return error_handler("Error: Failed to download file <b>$downloadfile<b>:<br>$!<br>");
4. Get the file size:
my  $downloadfilesize = (stat($fullpathdownloadfile))[7]
  or return error_handler("Error: Failed to get file size for <b>$downloadfile<b>:<br>$!<br>");
5. Set the HTTP headers properly:
$self->header_props(
                    '-type'                => 'application/x-download',
                    '-content-disposition' => "attachment;filename=$downloadfile",
                    '-content_length'      => $downloadfilesize,
                   );
6. Send the variable contents to the browser:
return $output;

Check the following files for a working demo for downloading files:
  • downloadapp.pl, the application wrapper
  • DownloadApp.pm, the application module
  • downloadapp1.tmpl.html, the 1st screen's HTML template
  • downloadapp2.tmpl.html, the 2nd screen's HTML template
The demo itself should look like this.

Last modified: Wed Sep 7 10:59:44 EDT 2016