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Re: Re: Find duplicate files.

by bikeNomad (Priest)
on Jun 02, 2001 at 21:13 UTC ( #85211=note: print w/replies, xml ) Need Help??

in reply to Re: Find duplicate files.
in thread Find duplicate files.

For just comparing files, it might be enough to do a CRC32 and use this along with the file size. This has the added advantage of allowing quick scans through ZIP files for dupes as well (using Archive::Zip of course) because ZIP files already have crc32 values in them.

The CRC32 found in Compress::Zlib runs 82% faster than Digest::MD5 on my system, using the following benchmark program:

#!/usr/bin/perl -w use strict; use IO::File; use Compress::Zlib (); use Digest::MD5; use Benchmark; use constant BUFSIZE => 32768; sub crc32 { my $fh = shift; binmode($fh); sysseek($fh, 0, 0); # rewind my $buffer = ' ' x BUFSIZE; my $crc = 0; while ($fh->sysread($buffer, BUFSIZE)) { $crc = Compress::Zlib::crc32($buffer, $crc); } return $crc; } sub md5 { my $fh = shift; seek($fh, 0, 0); # rewind my $md5 = Digest::MD5->new(); $md5->addfile($fh); return $md5->digest; } foreach my $file (@ARGV) { my $fh = IO::File->new($file); binmode($fh); next if !defined($fh); Benchmark::cmpthese(-10, { "crc32 $file", sub { crc32($fh) }, "md5 $file", sub { md5($fh) } }); }

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