kernel-source/fdupes_relink

#!/usr/bin/perl
use strict;
use warnings;

$/="";
while (<>) {
	chomp;

	my %dups; # hash: inode -> array of filenames
	foreach (split /\n/) {
		my $inode = (stat)[1];
		push @{$dups{$inode}}, $_;
	}

	my @keys = keys(%dups);

	# all are hardlinks to the same data
	next if (scalar @keys < 2);

	# sort by nlink
	@keys = sort { scalar $dups{$a} <=> scalar $dups{$b} } @keys;
	my $target = $dups{shift @keys}[0];

	foreach (@keys) {
		foreach (@{$dups{$_}}) {
			print "relinking $_ -> $target\n";
			unlink($_);
			link($target, $_) or die "link failed";
		}
	}
}