nix/scripts/nix-collect-garbage.in

#! @perl@ -w

use strict;
use IPC::Open2;

my $rootsDir = "@localstatedir@/nix/gcroots";
my $storeDir = "@storedir@";

my %alive;

my $keepSuccessors = 1;
my $invert = 0;

my @roots = ();


# Parse the command line.
foreach my $arg (@ARGV) {
    if ($arg eq "--no-successors") { $keepSuccessors = 0; }
    elsif ($arg eq "--invert") { $invert = 1; }
    else { die "unknown argument `$arg'" };
}


# Read all GC roots from the given file.
sub readRoots {
    my $fileName = shift;
    open ROOT, "<$fileName" or die "cannot open `$fileName': $!";
    while (<ROOT>) {
        chomp;
        foreach my $root (split ' ') {
            die "bad root `$root' in file `$fileName'"
                unless $root =~ /^\S+$/;
            push @roots, $root;
        }
    }
    close ROOT;
}


# Recursively finds all *.gcroot files in the given directory.
sub findRoots;
sub findRoots {
    my $followSymlinks = shift;
    my $dir = shift;

    opendir(DIR, $dir) or die "cannot open directory `$dir': $!";
    my @names = readdir DIR or die "cannot read directory `$dir': $!";
    closedir DIR;

    foreach my $name (@names) {
        next if $name eq "." || $name eq "..";
        $name = $dir . "/" . $name;
        if ($name =~ /.gcroot$/ && -f $name) {
            readRoots $name;
        }
        elsif (-d $name) {
            if ($followSymlinks || !-l $name) {
                findRoots 0, $name;
            }
        }
    }
    
}


# Find GC roots, starting at $rootsDir.
findRoots 1, $rootsDir;


# Determine all store paths reachable from the roots.
my $extraarg = "";
if ($keepSuccessors) { $extraarg = "--include-successors"; };
my $pid = open2(\*READ, \*WRITE, "@bindir@/nix-store --query --requisites $extraarg @roots") 
    or die "determining live paths";
close WRITE;
while (<READ>) {
	chomp;
	$alive{$_} = 1;
	if ($invert) { print "$_\n"; };
}
close READ;

waitpid $pid, 0;
$? == 0 or die "determining live paths";

exit 0 if ($invert);


# Using that information, find all store paths *not* reachable from
# the roots.
opendir(DIR, $storeDir) or die "cannot open directory $storeDir: $!";
foreach my $name (readdir DIR) {
    next if ($name eq "." || $name eq "..");
    $name = "$storeDir/$name";
    if (!$alive{$name}) {
        print "$name\n";
    }
}
closedir DIR;