Check out File::Type

#!/usr/bin/perl -w
use strict;
use File::Type;

my $filename = 'myfile.zip';
my $filetype = File::Type->new();
my $type     = $filetype->checktype_filename($filename);
my $zipped   = ($type eq 'application/zip');

print "$filename is of type $type (", $zipped ? '' : 'not ', "zipped)\
+n";
[download]

When you say "zipped" do you mean "compressed" or do you mean that a specific compression algorithm/tool was used (i.e., Windows PKZIP format)?

File::Type can also tell you if the file is compressed in other ways, though you'll have to check the return value for each type.

-- Eric Hammond

1. call qx[ file $file ] and grep if the output says it's a ZIP file
2. read the first few bytes and see if they match the string PK\003\004
3. use Archive::Zip (this may or may not help)

open(F, "file.zip") || die "File open failed: $!\n";
if(read(F, $buffer, 2)){
  if($buffer eq 'PK'){
    print "We have a zip\n";
  }else{
    print "No zip here\n";
  }
}
close(F);
[download]

Aren't you assuming a specific tool was used to do the zipping, though? Or, is that a universal standard?

Try this (requires the Archive::Zip module):

use Archive::Zip;
$zip = Archive::Zip->new();
die "Invalid zip file!" if $zip->read("zipfile.zip") != AZ_OK;
[download]

Update:You may need some of the other Archive modules if you want to check for gzipped files.

As far as I know all Windows/DOS based .ZIP archives start with PK. This however is not the case for gzip(.gz) files.

You can check the first 2 bytes of the file. If they are PK, then you have a .zip file.

Or, to be slightly more accurate, if they are not PK you know that you don't have a .zip file :-)

There is nothing to stop a non-zip file starting with PK.

If you want to be sure use Archive::Zip to attempt to extract the file or check the file's CRCs.

You need the mime magic library (have a look at /etc/mime-magic on linux). The File (1) command uses this, and a quick search on CPAN reveals a File::MMagic module which purports to do something similar.