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#!/usr/bin/perl
open( NEED, ">&=3" ) || die( "Couldn't open output for needed files!?!" );
while( defined($alternative_file = glob("/var/lib/dpkg/alternatives/*")) )
{
$name = "$1" if $alternative_file =~ m{^.*/([^/]*)$};
open( FILE, $alternative_file ) || die( "Couldn't open $alternative_file\n" );
my $mode = <FILE>;
my $winner_name = readlink '/etc/alternatives/'.$name or die "Unable to read symlink $name";
#
# parse the first stanza: the names of the symlinks
#
# @link holds pairs: name of the file in alternatives dir; path of the alternative
# e.g.: editor, /usr/bin/editor
# editor.1.gz, /usr/share/man/man1/editor.1.gz
# ...
# entry number 0 is the master, the rest are slaves
my @link;
$link[0][0] = $name;
$_ = <FILE>; chomp($_);
$link[0][1] = $_;
my $num_files = 1;
while (1) {
$_ = <FILE>; chomp($_);
last unless $_;
$link[$num_files][0] = $_;
$_ = <FILE>; chomp($_);
$link[$num_files][1] = $_;
$num_files++;
}
#
# parse the stanzas with files provided by packages
#
my %alternative;
my $winner = undef;
ALT: while( $master = <FILE> ) {
chomp($master);
last ALT if $master eq "";
die "internal error: duplicate master [$master] in alternatives file $name" if exists $alternative{$master};
my $pri = <FILE>; chomp($pri);
my $this = $alternative{$master} = { prio => $pri, files => [ $master ] };
$winner = $this if $master eq $winner_name;
SLAVE: for ( $i = 1; $i < $num_files; $i++ ) {
$slave = <FILE>; chomp($slave);
$alternative{$master}->{files}->[$i] = $slave;
}
}
warn("Master link \"/etc/alternatives/$name\" points to alternative \"${winner_name}\", but no such alternative is registered, according to \"/var/lib/dpkg/alternatives/$name\". See \"update-alternatives --display $name\"\n"), next unless defined $winner;
# list the symlinks for files the winning alternative provides
for ($i = 0; $i < $num_files; $i++) {
print '/etc/alternatives/', $link[$i][0], "\n", $link[$i][1], "\n" or die $! if $winner->{files}->[$i];
}
}
close STDOUT or die $!;
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