Reference for Chris - dupe merge

Posting this for reference, for Chris, and for anyone else who manages LARGE sets of media files. I've been using this script for 10 years, here is the latest version:

=========


#!/usr/bin/perl -w
use strict;
use Fcntl qw(:DEFAULT :flock);
use File::Compare;
use File::Temp;

# Copyright (C) 2002-2010 Zygo Blaxell

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

my $input_links = 0;
my $input_files = 0;
my $input_bogons = 0;
my $hash_bytes = 0;
my $hash_files = 0;
my $hash_errors = 0;
my $compare_bytes = 0;
my $compare_count = 0;
my $compare_errors = 0;
my $compare_differences = 0;
my $trivially_unique = 0;
my $merges_attempted = 0;
my $hard_links = 0;
my $link_errors = 0;
my $link_retries = 0;
my $recovered_bytes = 0;
my $recovered_files = 0;
my $lost_files = 0;
my $lost_bytes = 0;
my $surprises = 0;

eval '
use Digest::SHA1 qw(sha1 sha1_hex sha1_base64);
';

if ($@) {
warn "Digest::SHA1: $@\nUsing external md5sum program to generate hashes.\nPlease install Digest::SHA1 (libdigest-sha1-perl)";

eval <<'DIGEST';
sub really_digest {
my ($filename) = (@_);
my $fv = open(MD5SUM, "-|");
die "fork: $!" unless defined($fv);
if ($fv) {
my ($sum_line) = ;
close(MD5SUM) or die "md5sum: exit status $? (error status $!)";
die "hash error:  got EOF instead of md5sum output" unless defined($sum_line);
my ($sum) = $sum_line =~ m/^([a-fA-F0-9]{32})/o;
die "hash error:  got \Q$sum_line\E instead of md5sum output" unless defined($sum);
return $sum;
} else {
sysopen(STDIN, $filename, O_RDONLY|O_NONBLOCK) or die "open: $filename: $!";
exec('md5sum');
# Perl guarantees it will die here
}
}
DIGEST
} else {
eval <<'DIGEST';
sub really_digest {
my ($filename) = (@_);
die "'$filename' is not a plain file" if (-l $filename) || ! (-f _);
my $ctx = Digest::SHA1->new;
sysopen(FILE, $filename, O_RDONLY|O_NONBLOCK) or die "open: $filename: $!";
binmode(FILE); # FIXME:  Necessary?  Probably harmless...
$ctx->addfile(\*FILE);
close(FILE) or die "close: $filename: $!";
return $ctx->b64digest;
}
DIGEST
}

my $collapse_access = 0;
my $collapse_timestamp = 0;
my $collapse_zero = 0;
my $skip_compares = 0;
my $skip_compare_preference = 0;
my $skip_hashes = 0;
my $skip_hashes_threshold = 0;
my $progress = 0;
my $verbose = 0;
my $debug = 0;
my $dry_run = 0;
my $humane = 0;
my @extra_find_opts = ();
my @extra_sort_opts = ();
my $lock_file;
my $lock_rm = 0;
my $lock_obtained = 0;

sub digest {
my ($filename) = (@_);
if ($skip_hashes) {
return "SKIPPING HASHES";
} else {
print STDERR 'H' if $progress;
my $digest = &really_digest($filename);
$hash_bytes += -s $filename;
$hash_files++;
return $digest
}
}

my @directories;

sub usage {
my $name = shift(@_);
die <
Usage: $name [--opts] directory [directory...]
Finds duplicate files in the given directories, and replaces all identical
copies of a file with hard-links to a single file.

Several options modify the definition of a "duplicate".  By default, files
which have differences in owner uid or gid, permission (mode), or
modification time (mtime) are considered different, so that hardlinking
files does not also change their attributes.  Additionally, all files of
zero size are ignored for performance reasons (there tend to be many
of them, and they tend not to release any space when replaced with
hard links).

        --access        uid, gid, and mode may be different for identical
                        files

        --debug         show all steps in duplication discovery process
                        (implies --verbose)

        --dry-run       do not lock files or make changes to filesystem

        --find          pass next options (up to --) to find command

        --humane        human-readable statistics (e.g. 1 048 576)

        --lock FILE     exit immediately (status 10) if unable to obtain a
                        flock(LOCK_EX|LOCK_NB) on FILE

        --lock-rm       remove lock file at exit

        --progress      output single-character progress indicators:
                        C - compare
                        H - hash
                        L - link(2)
                        R - rename(2)
                        S, s - lstat(2) (see source for details)
                        U - unlink(2)
                        . - all inodes with similar attributes done
                        (123456) - current file size in bytes

        --sort          pass next options (up to --) to sort command

        --timestamps    mtime may be different for identical files

        --skip-compare  skip byte-by-byte file comparisons

        --skip-hash[=N] skip calculation of hash function on files
                        larger than N bytes (default 1M).
                        Scalars KMGT specify KiB, MiB, GiB, and TiB.
                        Scalars kmgt specify KB, MB, GB, and TB.

        --trust         old name for --skip-compare
                        (trust the hash function)

        --verbose       report files as they are considered

        --zeros         hard-link zero-length files too
USAGE
}

while ($#ARGV >= 0) {
my $arg = shift(@ARGV);
if ($arg eq '--access') {
$collapse_access = 1;
} elsif ($arg eq '--timestamps') {
$collapse_timestamp = 1;
} elsif ($arg eq '--zeros') {
$collapse_zero = 1;
} elsif ($arg eq '--trust' || $arg eq '--skip-compare') {
$skip_compares = $skip_compare_preference = 1;
} elsif ($arg =~ /^--skip-hash(?:=(\d+)([KkMmGgTt]?))?$/os) {
my ($quantity, $unit) = ($1, $2);
$unit ||= '_';
$quantity ||= 1048576;
my %scale = (
_ => 1,
k => 1000,
K => 1024,
m => 1000*1000,
M => 1024*1024,
g => 1000*1000*1000,
G => 1024*1024*1024,
t => 1000*1000*1000*1000,
T => 1024*1024*1024*1024,
);
$skip_hashes = 0;
$skip_hashes_threshold = $quantity * $scale{$unit};
} elsif ($arg eq '--progress') {
$progress = 1;
} elsif ($arg eq '--verbose') {
$verbose = 1;
} elsif ($arg eq '--lock-rm') {
$lock_rm = 1;
} elsif ($arg eq '--lock') {
$lock_file = shift(@ARGV);
unless (defined($lock_file)) {
usage($0);
exit(1);
}
} elsif ($arg eq '--debug') {
$debug = $verbose = 1;
} elsif ($arg eq '--dry-run') {
$dry_run = 1;
} elsif ($arg eq '--humane') {
$humane = 1;
} elsif ($arg eq '--find') {
while ($#ARGV >= 0) {
my $extra_arg = shift(@ARGV);
last if $extra_arg eq '--';
push(@extra_find_opts, $extra_arg);
}
} elsif ($arg eq '--sort') {
while ($#ARGV >= 0) {
my $extra_arg = shift(@ARGV);
last if $extra_arg eq '--';
push(@extra_sort_opts, $extra_arg);
}
} elsif ($arg =~ /^-/o) {
usage($0);
exit(1);
} else {
push(@directories, $arg);
}
}

@directories or usage($0);

if (defined($lock_file) && !$dry_run) {
sysopen(LOCK_FILE, $lock_file, O_CREAT|O_RDONLY, 0666) or die "open: $lock_file: $!";
flock(LOCK_FILE, LOCK_EX|LOCK_NB) or die "flock: $lock_file: LOCK_EX|LOCK_NB: $!";
print STDERR "Locked '$lock_file' in LOCK_EX mode.\n" if $verbose;
$lock_obtained = 1;
}

END {
if ($lock_obtained && !$dry_run) {
print STDERR "Removing '$lock_file'.\n" if $verbose;
unlink($lock_file) or warn "unlink: $lock_file: $!";
}
}

sub tick_quote {
my ($text) = (@_);
$text =~ s/'/'\\''/go;
return "'$text'";
}

my @find_command = ('find', @directories, @extra_find_opts, '-type', 'f');
my $printf_string = '%s ' .
($collapse_access    ? '0 0 0 ' : '%U %G %m ') .
($collapse_timestamp ? '0 '     : '%T@ ') .
'%D %i %p\0';

push(@find_command, '!', '-empty') unless $collapse_zero;
push(@find_command, '-printf', $printf_string);

my @sort_command = ('sort', '-znr', @extra_sort_opts);
my @quoted_sort_command = @sort_command;
grep(tick_quote($_), @quoted_sort_command);
my $quoted_sort_command = "'" . join("' '", @quoted_sort_command) . "'";

my @quoted_find_command = @find_command;
grep(tick_quote($_), @quoted_find_command);
my $quoted_find_command = "'" . join("' '", @quoted_find_command) . "'";
print STDERR "find command:  $quoted_find_command | $quoted_sort_command\n" if $verbose;

open(FIND, "$quoted_find_command | $quoted_sort_command |") or die "open: $!";
$/ = "\0";

# Input is sorted so that all weak keys are contiguous.
# When the key changes, we have to process all files we previously know about.
my $current_key = -1;

# $inode_to_file_name{$inode} = [@file_names]
my %inode_to_file_name = ();

# Link files
sub link_files {
my ($from, $to) = (@_);

my $quoted_from = tick_quote($from);
my $quoted_to = tick_quote($to);
print STDERR "\n" if $progress;
print STDERR "ln -f $quoted_from $quoted_to\n";

return if $dry_run;

my $inode_dir = $to;
my $inode_base = $to;
$inode_dir =~ s:[^/]*$::o;
$inode_base =~ s:^.*/::os;
my $tmp_to = File::Temp::tempnam($inode_dir, ".$inode_base.");
print STDERR "\tlink: $from -> $tmp_to\n" if $debug;
print STDERR 'L' if $progress;
link($from, $tmp_to) or die "link: $from -> $tmp_to: $!";
print STDERR "\trename: $tmp_to -> $to\n" if $debug;
print STDERR 'R' if $progress;
unless (rename($tmp_to, $to)) {
my $saved_bang = $!;
print STDERR 'U' if $progress;
unlink($tmp_to) or warn "unlink: $tmp_to: $!"; # Try, possibly in vain, to clean up
die "rename: $tmp_to -> $from: $saved_bang";
}
}

# Convert $dev,$ino into a single string where lexical and numeric orderings are equivalent
sub format_inode ($$) {
my ($dev, $ino) = @_;
# 64 bits ought to be enough for everybody!
return sprintf('%016x:%016x', $dev, $ino);
}

# Process all known files so far.
sub merge_files {
$merges_attempted++;

my %hash_to_inode;
# Used to stop link retry loops (there is a goto in here!  Actually two...)
my %stop_loop;

my @candidate_list = keys(%inode_to_file_name);
$input_files += @candidate_list;
if (@candidate_list < 2) {
print STDERR "Merging...only one candidate to merge..." if $debug;
$trivially_unique++;
goto end_merge;
}

print STDERR "Merging...\n" if $debug;
foreach my $candidate (sort @candidate_list) {
print STDERR "\tDigesting candidate $candidate\n" if $debug;
my $ok = 0;
my $digest;

hash_file:

foreach my $filename (sort keys(%{$inode_to_file_name{$candidate}})) {
print STDERR "\t\tDigesting file $filename\n" if $debug;
if ((-l $filename) || ! -f _) {
print STDERR "\n" if $progress;
warn "Bogon file " . tick_quote($filename);
$input_bogons++;
delete $inode_to_file_name{$candidate}->{$filename};
next;
}
eval {
$digest = digest($filename);
};
if ($@) {
warn "Digest($filename)(#$candidate) failed: $@";
$hash_errors++;
} else {
$ok = 1;
last hash_file;
}
}
if ($ok) {
print STDERR "\t\tDigest is $digest\n" if $debug;

my $incumbent_list = ($hash_to_inode{$digest} ||= []);
my $incumbent_matched = 0;
for my $incumbent (sort @$incumbent_list) {
print STDERR "\t\tInodes $incumbent and $candidate have same hash\n" if $debug;

my $finished = 0;

link_start:

until ($finished) {
my @incumbent_names = sort keys(%{$inode_to_file_name{$incumbent}});
my @candidate_names = sort keys(%{$inode_to_file_name{$candidate}});
print STDERR "\t\tLinks to $incumbent:", join("\n\t\t\t", '', @incumbent_names), "\n" if $debug;
print STDERR "\t\tLinks to $candidate:", join("\n\t\t\t", '', @candidate_names), "\n" if $debug;

incumbent_file:

foreach my $incumbent_file (@incumbent_names) {
print STDERR 'S' if $progress;
my ($incumbent_dev,$incumbent_ino,$incumbent_mode,$incumbent_nlink,$incumbent_uid,$incumbent_gid,$incumbent_rdev,$incumbent_size,$incumbent_atime,$incumbent_mtime,$incumbent_ctime,$incumbent_blksize,$incumbent_blocks) = lstat($incumbent_file);
print STDERR "\t\tINCUMBENT dev=$incumbent_dev ino=$incumbent_ino mode=$incumbent_mode nlink=$incumbent_nlink uid=$incumbent_uid gid=$incumbent_gid rdev=$incumbent_rdev size=$incumbent_size atime=$incumbent_atime mtime=$incumbent_mtime ctime=$incumbent_ctime blksize=$incumbent_blksize blocks=$incumbent_blocks _=$incumbent_file\n" if $debug;

if (!defined($incumbent_blocks) || ! (-f _)) {
warn "lstat: $incumbent_file: $!";
$surprises++;
next incumbent_file;
}

if (format_inode($incumbent_dev, $incumbent_ino) ne $incumbent) {
warn "$incumbent_file: expected inode $incumbent, found ".format_inode($incumbent_dev, $incumbent_ino);
$surprises++;
next incumbent_file;
}

my $at_least_one_link_done = 0;

candidate_file:

foreach my $candidate_file (@candidate_names) {
print STDERR 's' if $progress;
my ($candidate_dev,$candidate_ino,$candidate_mode,$candidate_nlink,$candidate_uid,$candidate_gid,$candidate_rdev,$candidate_size,$candidate_atime,$candidate_mtime,$candidate_ctime,$candidate_blksize,$candidate_blocks) = lstat($candidate_file);
print STDERR "\t\t\tCANDIDATE dev=$candidate_dev ino=$candidate_ino mode=$candidate_mode nlink=$candidate_nlink uid=$candidate_uid gid=$candidate_gid rdev=$candidate_rdev size=$candidate_size atime=$candidate_atime mtime=$candidate_mtime ctime=$candidate_ctime blksize=$candidate_blksize blocks=$candidate_blocks _=$candidate_file\n" if $debug;

if (!defined($candidate_blocks) || ! (-f _)) {
warn "lstat: $candidate_file: $!";
$surprises++;
next candidate_file;
}

if (format_inode($candidate_dev, $candidate_ino) ne $candidate) {
warn "$candidate_file: expected inode $candidate, found ".format_inode($candidate_dev, $candidate_ino);
$surprises++;
next candidate_file;
}

if ($candidate_size != $incumbent_size) {
warn "$candidate_file, $incumbent_file: file sizes are different";
$surprises++;
next candidate_file;
}

my $identical;

eval {
if ($skip_compares) {
print STDERR "\t\t\t\tSkipping compare!\n" if $debug;
$identical = 1;
} else {
my $quoted_incumbent_file = tick_quote($incumbent_file);
my $quoted_candidate_file = tick_quote($candidate_file);
print STDERR "cmp $quoted_incumbent_file $quoted_candidate_file\n" if $debug;
print STDERR 'C' if $progress;
if (compare($incumbent_file, $candidate_file)) {
$compare_differences++;
$identical = 0;
# It is significant for two non-identical files to have identical SHA1 or MD5 hashes.
# Some kind of I/O error is more likely, so this message cannot be turned off.
# On the other hand, if we're skipping hashes, _all_ files will have the same hash,
# so the warning in that case is quite silly.  Hmmm.
print STDERR "$quoted_incumbent_file and $quoted_candidate_file have same hash but do not compare equal!\n" unless $skip_hashes;
} else {
$identical = 1;
$incumbent_matched = 1;
}
$compare_count++;
$compare_bytes += $incumbent_size;
}
};
if ($@) {
warn $@;
$compare_errors++;
next candidate_file;
}

if ($identical) {
print STDERR "\t\t\t\tincumbent_nlink=$incumbent_nlink, candidate_nlink=$candidate_nlink\n" if $debug;

# We have to do this to break out of a possible infinite loop.
# Given file A, with hardlinks A1 and A2, and file B, with hardlink B1,
# such that A1 and B1 are in non-writable directories, we will loop
# forever hardlinking A2 with A and B.
# To break the loop, we never attempt to hardlink any files X and Y twice.

if (defined($stop_loop{$incumbent_file}->{$candidate_file}) ||
   defined($stop_loop{$candidate_file}->{$incumbent_file})) {
print STDERR "Already considered linking '$incumbent_file' and '$candidate_file', not trying again now\n";
} else {
$stop_loop{$incumbent_file}->{$candidate_file} = 1;
$stop_loop{$candidate_file}->{$incumbent_file} = 1;

my $link_done = 0;

my ($from_file, $to_file, $from_inode, $to_inode, $from_nlink, $to_nlink);

# If the candidate has more links than incumbent, replace incumbent with candidate.
# If the incumbent has more links than candidate, replace candidate with incumbent.
# If the link counts are equal, we saw incumbent first, so keep the incumbent.
# "We saw incumbent first" is significant because we explicitly sort the inodes.
# Thank Johannes Niess for this idea.
if ($candidate_nlink > $incumbent_nlink) {
$from_file = $candidate_file;
$to_file = $incumbent_file;
$from_inode = $candidate;
$to_inode = $incumbent;
$from_nlink = $candidate_nlink;
$to_nlink = $incumbent_nlink;
} else {
$to_file = $candidate_file;
$from_file = $incumbent_file;
$to_inode = $candidate;
$from_inode = $incumbent;
$to_nlink = $candidate_nlink;
$from_nlink = $incumbent_nlink;
}

eval {
link_files($from_file, $to_file);
$link_done = 1;
};

if ($@) {
warn $@;
$link_errors++;

print STDERR "\t\t\t\t...retrying with swapped from/to files...\n" if $debug;
$link_retries++;

eval {
($from_file, $to_file) = ($to_file, $from_file);
($from_inode, $to_inode) = ($to_inode, $from_inode);
($from_nlink, $to_nlink) = ($to_nlink, $from_nlink);
link_files($from_file, $to_file);
$link_done = 1;
};

if ($@) {
warn $@;
$link_errors++;
}
}

# Note since the files are presumably identical, they both have the same size.
# My random number generator chooses the incumbent's size.

if ($link_done) {
delete $inode_to_file_name{$to_inode}->{$to_file};
$inode_to_file_name{$from_inode}->{$to_file} = undef unless ($dry_run);
$hash_to_inode{$digest} = [ $from_inode ];

$hard_links++;
if ($to_nlink == 1) {
$recovered_files++;
$recovered_bytes += $incumbent_size;
}

# FIXME:  Now we're really confused for some reason.
# Start over to rebuild state.
next link_start;
} else {
warn "Could not hardlink '$incumbent_file' and '$candidate_file'";

# FIXME:  This is a lame heuristic.  We really need to know if we've
# tried all possible ways to hardlink the file out of existence first;
# however, that is complex and only benefits a silly statistic.
if ($to_nlink == 1 || $from_nlink == 1) {
$lost_files++;
$lost_bytes += $incumbent_size;
}
}
}
}
}
}
$finished = 1;
}
}
unless ($incumbent_matched) {
print STDERR "\t\tNew hash entered\n" if $debug;
push(@$incumbent_list, $candidate);
}
} else {
warn "No digests found for inode $candidate\n";
delete $inode_to_file_name{$candidate};
}
}
print STDERR '.' if $progress;

end_merge:

print STDERR "Merge done.\n" if $debug;
undef %inode_to_file_name;
}

my $last_time = 0;
my $last_size = 0;

while () {
my ($weak_key, $size, $dev, $ino, $name) = m/^((\d+) \d+ \d+ \d+ -?[\d.]+) (\d+) (\d+) (.+)\0$/so;
die "read error: $!\nLast input line was '$_'" unless defined($name);

my $inode = format_inode($dev, $ino);

print STDERR "weak_key=$weak_key inode=$inode name=$name\n" if $debug;

if ($skip_hashes_threshold && $size >= $skip_hashes_threshold) {
$skip_hashes = 1;
$skip_compares = 0;
} else {
$skip_hashes = 0;
$skip_compares = $skip_compare_preference;
}

if ($progress) {
my $this_time = time();
if ($this_time != $last_time && $size != $last_size) {
$last_time = $this_time;
$last_size = $size;
print STDERR "($size)";
}
}

$input_links++;
merge_files if $weak_key ne $current_key;
$current_key = $weak_key;

$inode_to_file_name{$inode}->{$name} = undef;

print STDERR "$name\n" if $verbose;
}

merge_files;

my $stats_blob = <
compare_bytes           $compare_bytes
compare_count           $compare_count
compare_differences     $compare_differences
compare_errors          $compare_errors
hard_links              $hard_links
hash_bytes              $hash_bytes
hash_errors             $hash_errors
hash_files              $hash_files
input_bogons            $input_bogons
input_files             $input_files
input_links             $input_links
link_errors             $link_errors
link_retries            $link_retries
lost_bytes              $lost_bytes
lost_files              $lost_files
merges_attempted        $merges_attempted
recovered_bytes         $recovered_bytes
recovered_files         $recovered_files
surprises               $surprises
trivially_unique        $trivially_unique
STATS

if ($humane) {
my $max_num_len = 0;

sub measure_numbers {
my ($num) = @_;
my $len = length($num);
$len += int( (length($num) - 1) / 3);
$max_num_len = $len if $len > $max_num_len;
}

(my $dummy = $stats_blob) =~ s/\d+/measure_numbers($&)/geos;

sub space_numbers {
my ($num) = @_;
1 while $num =~ s/(\d)(\d\d\d)((?: \d\d\d)*)$/$1 $2$3/os;
$num = ' ' x ($max_num_len - length($num)) . $num;
return $num;
}

$stats_blob =~ s/\d+/space_numbers($&)/geos;
}

$stats_blob =~ s/([^\n]*\n[^\n]*? )(\s+)( [^\n]*\n)/$1 . ('.' x length($2)) . $3/oemg;

print STDERR "\n" if $progress;
print STDERR $stats_blob;

exit(0);

__END__

#################################################################################
#                     GNU GENERAL PUBLIC LICENSE                                #
#                        Version 2, June 1991                                   #
#                                                                               #
#  Copyright (C) 1989, 1991 Free Software Foundation, Inc.                      #
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#  Everyone is permitted to copy and distribute verbatim copies                 #
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#                             Preamble                                          #
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#   The licenses for most software are designed to take away your               #
# freedom to share and change it.  By contrast, the GNU General Public          #
# License is intended to guarantee your freedom to share and change free        #
# software--to make sure the software is free for all its users.  This          #
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# Foundation's software and to any other program whose authors commit to        #
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#   The precise terms and conditions for copying, distribution and              #
# modification follow.                                                          #
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#                     GNU GENERAL PUBLIC LICENSE                                #
#    TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION            #
#                                                                               #
#   0. This License applies to any program or other work which contains         #
# a notice placed by the copyright holder saying it may be distributed          #
# under the terms of this General Public License.  The "Program", below,        #
# refers to any such program or work, and a "work based on the Program"         #
# means either the Program or any derivative work under copyright law:          #
# that is to say, a work containing the Program or a portion of it,             #
# either verbatim or with modifications and/or translated into another          #
# language.  (Hereinafter, translation is included without limitation in        #
# the term "modification".)  Each licensee is addressed as "you".               #
#                                                                               #
# Activities other than copying, distribution and modification are not          #
# covered by this License; they are outside its scope.  The act of              #
# running the Program is not restricted, and the output from the Program        #
# is covered only if its contents constitute a work based on the                #
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# Whether that is true depends on what the Program does.                        #
#                                                                               #
#   1. You may copy and distribute verbatim copies of the Program's             #
# source code as you receive it, in any medium, provided that you               #
# conspicuously and appropriately publish on each copy an appropriate           #
# copyright notice and disclaimer of warranty; keep intact all the              #
# notices that refer to this License and to the absence of any warranty;        #
# and give any other recipients of the Program a copy of this License           #
# along with the Program.                                                       #
#                                                                               #
# You may charge a fee for the physical act of transferring a copy, and         #
# you may at your option offer warranty protection in exchange for a fee.       #
#                                                                               #
#   2. You may modify your copy or copies of the Program or any portion         #
# of it, thus forming a work based on the Program, and copy and                 #
# distribute such modifications or work under the terms of Section 1            #
# above, provided that you also meet all of these conditions:                   #
#                                                                               #
#     a) You must cause the modified files to carry prominent notices           #
#     stating that you changed the files and the date of any change.            #
#                                                                               #
#     b) You must cause any work that you distribute or publish, that in        #
#     whole or in part contains or is derived from the Program or any           #
#     part thereof, to be licensed as a whole at no charge to all third         #
#     parties under the terms of this License.                                  #
#                                                                               #
#     c) If the modified program normally reads commands interactively          #
#     when run, you must cause it, when started running for such                #
#     interactive use in the most ordinary way, to print or display an          #
#     announcement including an appropriate copyright notice and a              #
#     notice that there is no warranty (or else, saying that you provide        #
#     a warranty) and that users may redistribute the program under             #
#     these conditions, and telling the user how to view a copy of this         #
#     License.  (Exception: if the Program itself is interactive but            #
#     does not normally print such an announcement, your work based on          #
#     the Program is not required to print an announcement.)                    #
#                                                                               #
# These requirements apply to the modified work as a whole.  If                 #
# identifiable sections of that work are not derived from the Program,          #
# and can be reasonably considered independent and separate works in            #
# themselves, then this License, and its terms, do not apply to those           #
# sections when you distribute them as separate works.  But when you            #
# distribute the same sections as part of a whole which is a work based         #
# on the Program, the distribution of the whole must be on the terms of         #
# this License, whose permissions for other licensees extend to the             #
# entire whole, and thus to each and every part regardless of who wrote it.     #
#                                                                               #
# Thus, it is not the intent of this section to claim rights or contest         #
# your rights to work written entirely by you; rather, the intent is to         #
# exercise the right to control the distribution of derivative or               #
# collective works based on the Program.                                        #
#                                                                               #
# In addition, mere aggregation of another work not based on the Program        #
# with the Program (or with a work based on the Program) on a volume of         #
# a storage or distribution medium does not bring the other work under          #
# the scope of this License.                                                    #
#                                                                               #
#   3. You may copy and distribute the Program (or a work based on it,          #
# under Section 2) in object code or executable form under the terms of         #
# Sections 1 and 2 above provided that you also do one of the following:        #
#                                                                               #
#     a) Accompany it with the complete corresponding machine-readable          #
#     source code, which must be distributed under the terms of Sections        #
#     1 and 2 above on a medium customarily used for software interchange; or,  #
#                                                                               #
#     b) Accompany it with a written offer, valid for at least three            #
#     years, to give any third party, for a charge no more than your            #
#     cost of physically performing source distribution, a complete             #
#     machine-readable copy of the corresponding source code, to be             #
#     distributed under the terms of Sections 1 and 2 above on a medium         #
#     customarily used for software interchange; or,                            #
#                                                                               #
#     c) Accompany it with the information you received as to the offer         #
#     to distribute corresponding source code.  (This alternative is            #
#     allowed only for noncommercial distribution and only if you               #
#     received the program in object code or executable form with such          #
#     an offer, in accord with Subsection b above.)                             #
#                                                                               #
# The source code for a work means the preferred form of the work for           #
# making modifications to it.  For an executable work, complete source          #
# code means all the source code for all modules it contains, plus any          #
# associated interface definition files, plus the scripts used to               #
# control compilation and installation of the executable.  However, as a        #
# special exception, the source code distributed need not include               #
# anything that is normally distributed (in either source or binary             #
# form) with the major components (compiler, kernel, and so on) of the          #
# operating system on which the executable runs, unless that component          #
# itself accompanies the executable.                                            #
#                                                                               #
# If distribution of executable or object code is made by offering              #
# access to copy from a designated place, then offering equivalent              #
# access to copy the source code from the same place counts as                  #
# distribution of the source code, even though third parties are not            #
# compelled to copy the source along with the object code.                      #
#                                                                               #
#   4. You may not copy, modify, sublicense, or distribute the Program          #
# except as expressly provided under this License.  Any attempt                 #
# otherwise to copy, modify, sublicense or distribute the Program is            #
# void, and will automatically terminate your rights under this License.        #
# However, parties who have received copies, or rights, from you under          #
# this License will not have their licenses terminated so long as such          #
# parties remain in full compliance.                                            #
#                                                                               #
#   5. You are not required to accept this License, since you have not          #
# signed it.  However, nothing else grants you permission to modify or          #
# distribute the Program or its derivative works.  These actions are            #
# prohibited by law if you do not accept this License.  Therefore, by           #
# modifying or distributing the Program (or any work based on the               #
# Program), you indicate your acceptance of this License to do so, and          #
# all its terms and conditions for copying, distributing or modifying           #
# the Program or works based on it.                                             #
#                                                                               #
#   6. Each time you redistribute the Program (or any work based on the         #
# Program), the recipient automatically receives a license from the             #
# original licensor to copy, distribute or modify the Program subject to        #
# these terms and conditions.  You may not impose any further                   #
# restrictions on the recipients' exercise of the rights granted herein.        #
# You are not responsible for enforcing compliance by third parties to          #
# this License.                                                                 #
#                                                                               #
#   7. If, as a consequence of a court judgment or allegation of patent         #
# infringement or for any other reason (not limited to patent issues),          #
# conditions are imposed on you (whether by court order, agreement or           #
# otherwise) that contradict the conditions of this License, they do not        #
# excuse you from the conditions of this License.  If you cannot                #
# distribute so as to satisfy simultaneously your obligations under this        #
# License and any other pertinent obligations, then as a consequence you        #
# may not distribute the Program at all.  For example, if a patent              #
# license would not permit royalty-free redistribution of the Program by        #
# all those who receive copies directly or indirectly through you, then         #
# the only way you could satisfy both it and this License would be to           #
# refrain entirely from distribution of the Program.                            #
#                                                                               #
# If any portion of this section is held invalid or unenforceable under         #
# any particular circumstance, the balance of the section is intended to        #
# apply and the section as a whole is intended to apply in other                #
# circumstances.                                                                #
#                                                                               #
# It is not the purpose of this section to induce you to infringe any           #
# patents or other property right claims or to contest validity of any          #
# such claims; this section has the sole purpose of protecting the              #
# integrity of the free software distribution system, which is                  #
# implemented by public license practices.  Many people have made               #
# generous contributions to the wide range of software distributed              #
# through that system in reliance on consistent application of that             #
# system; it is up to the author/donor to decide if he or she is willing        #
# to distribute software through any other system and a licensee cannot         #
# impose that choice.                                                           #
#                                                                               #
# This section is intended to make thoroughly clear what is believed to         #
# be a consequence of the rest of this License.                                 #
#                                                                               #
#   8. If the distribution and/or use of the Program is restricted in           #
# certain countries either by patents or by copyrighted interfaces, the         #
# original copyright holder who places the Program under this License           #
# may add an explicit geographical distribution limitation excluding            #
# those countries, so that distribution is permitted only in or among           #
# countries not thus excluded.  In such case, this License incorporates         #
# the limitation as if written in the body of this License.                     #
#                                                                               #
#   9. The Free Software Foundation may publish revised and/or new versions     #
# of the General Public License from time to time.  Such new versions will      #
# be similar in spirit to the present version, but may differ in detail to      #
# address new problems or concerns.                                             #
#                                                                               #
# Each version is given a distinguishing version number.  If the Program        #
# specifies a version number of this License which applies to it and "any       #
# later version", you have the option of following the terms and conditions     #
# either of that version or of any later version published by the Free          #
# Software Foundation.  If the Program does not specify a version number of     #
# this License, you may choose any version ever published by the Free Software  #
# Foundation.                                                                   #
#                                                                               #
#   10. If you wish to incorporate parts of the Program into other free         #
# programs whose distribution conditions are different, write to the author     #
# to ask for permission.  For software which is copyrighted by the Free         #
# Software Foundation, write to the Free Software Foundation; we sometimes      #
# make exceptions for this.  Our decision will be guided by the two goals       #
# of preserving the free status of all derivatives of our free software and     #
# of promoting the sharing and reuse of software generally.                     #
#                                                                               #
#                             NO WARRANTY                                       #
#                                                                               #
#   11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY    #
# FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN      #
# OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES        #
# PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED    #
# OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF          #
# MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS     #
# TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE        #
# PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,      #
# REPAIR OR CORRECTION.                                                         #
#                                                                               #
#   12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING   #
# WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR           #
# REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,    #
# INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING   #
# OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED     #
# TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY      #
# YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER    #
# PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE         #
# POSSIBILITY OF SUCH DAMAGES.                                                  #
#                                                                               #
#                      END OF TERMS AND CONDITIONS                              #
#                                                                               #
#             How to Apply These Terms to Your New Programs                     #
#                                                                               #
#   If you develop a new program, and you want it to be of the greatest         #
# possible use to the public, the best way to achieve this is to make it        #
# free software which everyone can redistribute and change under these terms.   #
#                                                                               #
#   To do so, attach the following notices to the program.  It is safest        #
# to attach them to the start of each source file to most effectively           #
# convey the exclusion of warranty; and each file should have at least          #
# the "copyright" line and a pointer to where the full notice is found.         #
#                                                                               #
#       #
#     Copyright (C)                                      #
#                                                                               #
#     This program is free software; you can redistribute it and/or modify      #
#     it under the terms of the GNU General Public License as published by      #
#     the Free Software Foundation; either version 2 of the License, or         #
#     (at your option) any later version.                                       #
#                                                                               #
#     This program is distributed in the hope that it will be useful,           #
#     but WITHOUT ANY WARRANTY; without even the implied warranty of            #
#     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             #
#     GNU General Public License for more details.                              #
#                                                                               #
#     You should have received a copy of the GNU General Public License         #
#     along with this program; if not, write to the Free Software               #
#     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA #
#                                                                               #
#                                                                               #
# Also add information on how to contact you by electronic and paper mail.      #
#                                                                               #
# If the program is interactive, make it output a short notice like this        #
# when it starts in an interactive mode:                                        #
#                                                                               #
#     Gnomovision version 69, Copyright (C) year  name of author                #
#     Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. #
#     This is free software, and you are welcome to redistribute it             #
#     under certain conditions; type `show c' for details.                      #
#                                                                               #
# The hypothetical commands `show w' and `show c' should show the appropriate   #
# parts of the General Public License.  Of course, the commands you use may     #
# be called something other than `show w' and `show c'; they could even be      #
# mouse-clicks or menu items--whatever suits your program.                      #
#                                                                               #
# You should also get your employer (if you work as a programmer) or your       #
# school, if any, to sign a "copyright disclaimer" for the program, if          #
# necessary.  Here is a sample; alter the names:                                #
#                                                                               #
#   Yoyodyne, Inc., hereby disclaims all copyright interest in the program      #
#   `Gnomovision' (which makes passes at compilers) written by James Hacker.    #
#                                                                               #
#   , 1 April 1989                                        #
#   Ty Coon, President of Vice                                                  #
#                                                                               #
# This General Public License does not permit incorporating your program into   #
# proprietary programs.  If your program is a subroutine library, you may       #
# consider it more useful to permit linking proprietary applications with the   #
# library.  If this is what you want to do, use the GNU Library General         #
# Public License instead of this License.                                       #
#################################################################################

Comments

Posted in full for posterity. Current downloadable link at:

http://hungrycats.org/~zblaxell/dupemerge/faster-dupemerge
Anonymous said…
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