Problematic UploadFile() method in CGI.pm

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

Most revered monks,

Lately I have been plunging myself into Perl's CGI, programming. And stumbled myself on some aspects of it which I can't seem to figure out the problem. Thus to you I turn for enlightenment....

I was trying to do a file upload through UploadFile() method in CGI.pm. It is done in this way.

  # Problematic Upload Entry
   strong('Choose File to upload: '),
       filefield(-name=>'upload',-size=>60),br,
[download]

However when I tried to capture the result. Although it can identify the file name, but it cannot identify it's value.

    
    my $file = param('upload');
    
    # This line print successfully
    print h2('File name'),      $file;


    # But not the subsequent lines
    # Line 55 begins here
    print h2('File MIME type'), uploadInfo($file)->{'Content-Type'};

   while (<$file>) {
        print;
        $length += length($_);
    }
    print h2('File length'), $length;
[download]

The error message given by the problematic line 55 is:

Can't use an undefined value as a HASH reference at /home/ewijaya/publ
+ic_html/MyTest/cgi-bin/price_debug.cgi line 55.
[download]

Furthere more if you comment out the uploadInfo($file)->{'Content-Type'} line. The content inside while loop doesn't get printed.

To my understanding, I have constructed the uploadInfo() method as according to the doc. But is there anything else that I missed here? The complete code listing can be found here:


#!/usr/bin/perl -w
use strict;
use CGI qw/:standard :html3/;
use CGI::Carp qw( fatalsToBrowser );

print header, start_html('Order Ice Cream with Price'),
         h1('Order Ice Cream with Price');


generate_form();
print_results();

sub generate_form {
    print hr, start_form,
        strong('Your email: '),
            textfield( -name => 'user_email' ), br, br

        strong('Cone: '),
            radio_group(
                -name     => 'cone',
                -multiple => 1,
                -values   => [qw/sugar waffle/]              
                ),
                br, br

                
        strong('Number of Units: '),
            textfield( -name => 'no_unit' ), br, br                   

        # Problematic Upload Entry
       strong('Choose File to upload: '),
            filefield(-name=>'upload',-size=>60),br,                  
+                                    
        submit( -value => 'Submit' ), 
        end_form, hr;
}


sub print_results {
    print  "You ordered  ",       
        param('no_unit'), ' unit of  ', param('cone'), ' cone.';
    print br;

    my $ct     = param('cone');
    my $nu     = param('no_unit');
    my $uemail =  param('user_email');

    my $length;

   
    my $file = param('upload');
      
     # This line print successfully
     print h2('File name'),      $file;

    # But not the subsequent lines
  
    print h2('File MIME type'), uploadInfo($file)->{'Content-Type'};
    while (<$file>) {
        print;
        $length += length($_);
    }
    print h2('File length'), $length;

    print br;

}
[download]

And it can be tested through this link.

Regards,
Edward

Comment on Problematic UploadFile() method in CGI.pm Select or Download Code

Replies are listed 'Best First'.
Re: Problematic UploadFile() method in CGI.pm by wfsp (Abbot) on May 20, 2006 at 19:16 UTC
The cgi docs give this example: `$fh = upload('uploaded_file'); while (<$fh>) { print; }` [download] CGI.pm creates a temporary file of the uploaded file. The above method gives you the file handle to that file. Hope that helps	[reply] [d/l]
Re: Problematic UploadFile() method in CGI.pm by ioannis (Abbot) on May 20, 2006 at 20:08 UTC
You need add a parenthesis to capture the hash reference, otherwise you will keep getting undef: print h2('File MIME type'), (uploadInfo($file))->{'Content-Type'};	[reply]
Re^2: Problematic UploadFile() method in CGI.pm by Errto (Vicar) on May 21, 2006 at 17:02 UTC
I don't believe that's correct. See this small example: `my $hash = { a => 'b' }; sub foo { print $_[0], "\n"; return $hash; } print foo('abcd')->{a};` [download] No parens required to use the arrow notation with a subroutine return value.	[reply] [d/l]
Re: Problematic UploadFile() method in CGI.pm by gellyfish (Monsignor) on May 21, 2006 at 10:38 UTC
you need to set the enctype of the form to 'multipart/form-data', CGI provides the `start_multipart_form` for this purpose which you should use instead of the plain `start_form` /J\	[reply] [d/l] [select]
Re: Problematic UploadFile() method in CGI.pm by ahmad (Hermit) on May 21, 2006 at 10:26 UTC
Hello First you'll need to get the file name to save it , if you're planning to do so ... actually i cant see that you're saving anything in your code `# First -- Get file name from our File Box my $file = param('upload'); # Strip out file path from file name , to be able to save it out in ou +r server $file =~ s/.[\/\\](.*)/$1/; # Next , Generate upload handle my $uph = upload("upload"); #now we save out our file using the name we already got open(OUT,">$file") or die $!; binmode(OUT); while(<$uph>){ print OUT $_; } close(OUT);` [download] now you should see the same file in your server (uploaded)	[reply] [d/l]