checking file types in a perl upload script

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

A friend of mine gave me a simple file upload program. Here's the file proccessing part:

if ( $q->param() ) {
    my $filehandle = $q->param('file');
    binmode($filehandle);

    open(OUT,">/var/www/html/toiletben/pictures/tempout") || die $!;
    binmode(OUT);

    # process $filehandle
    {
        my $buffer;
        while ( read($filehandle,$buffer,1024) ) {
            print OUT $buffer;
        }
    }

    close(OUT);

    print   $q->header,
            $q->start_html,
            $q->p('File uploaded'),
            $q->end_html;
    exit(0);
}
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Unfortunatly it's mostly uncommented, but I've made sense of most of it. My question is this: I want this script to only accept .jpg files so I need to know how to make this test.

As I understand it, the buffer just recieves a binary stream containing the file itself. How can I test for the file type?

Comment on checking file types in a perl upload script Download Code

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Re: checking file types in a perl upload script by rob_au (Abbot) on Feb 16, 2002 at 08:28 UTC
A simple search of this site would have revealed a number of nodes relating to CGI-based file upload, including one from myself here. This question could also have been answered by having a read through some of the documentation for CGI, specifically under the heading "Creating a file upload field". However, it should be noted, that you should not necessarily trust the extension of the file name supplied with the binary stream. As such, depending upon the intended application of the uploaded files, it would be wise to make use of a module such as File::MMagic (or the shell command `file` if installed), which allows for the identification of file types based upon file names and file content - This allows files to be verified that the file content type matches the name given. `perl -e 's&&rob@cowsnet.com.au&&&split/[@.]/&&s&.com.&_&&&print'`	[reply] [d/l]
Re: checking file types in a perl upload script by kwoff (Friar) on Feb 16, 2002 at 08:24 UTC
I assume you don't mean to match filename on /.jpg$/. If you read `perldoc -m Image::Size`, it shows what a JPEG header looks like.	[reply]