mirror of
https://github.com/privatevoid-net/nix-super.git
synced 2024-11-14 18:26:16 +02:00
61 lines
1.8 KiB
Perl
Executable file
61 lines
1.8 KiB
Perl
Executable file
#! /usr/bin/perl -w
|
|
|
|
use strict;
|
|
|
|
my $keep = 0;
|
|
|
|
if (scalar @ARGV > 0 && $ARGV[0] eq "--keep") {
|
|
shift @ARGV;
|
|
$keep = 1;
|
|
}
|
|
|
|
my $hash = $ARGV[0];
|
|
$hash || die "no package hash specified";
|
|
|
|
my $linkdir = "@localstatedir@/nix/links";
|
|
|
|
# Build the specified package, and all its dependencies.
|
|
my $pkgdir = `nix -qph $hash`;
|
|
if ($?) { die "`nix -qph' failed"; }
|
|
chomp $pkgdir;
|
|
|
|
# Figure out a generation number.
|
|
my $nr = 0;
|
|
while (-e "$linkdir/$nr") { $nr++; }
|
|
my $link = "$linkdir/$nr";
|
|
|
|
# Create a symlink from $link to $pkgdir.
|
|
symlink($pkgdir, $link) or die "cannot create $link: $!";
|
|
|
|
# Also store the hash of $pkgdir. This is useful for garbage
|
|
# collection and the like.
|
|
my $hashfile = "$linkdir/$nr.hash";
|
|
open HASH, "> $hashfile" or die "cannot create $hashfile";
|
|
print HASH "$hash\n";
|
|
close HASH;
|
|
|
|
my $current = "$linkdir/current";
|
|
|
|
# Read the current generation so that we can delete it (if --keep
|
|
# wasn't specified).
|
|
my $oldlink = readlink($current);
|
|
|
|
# Make $link the current generation by pointing $linkdir/current to
|
|
# it. The rename() system call is supposed to be essentially atomic
|
|
# on Unix. That is, if we have links `current -> X' and `new_current
|
|
# -> Y', and we rename new_current to current, a process accessing
|
|
# current will see X or Y, but never a file-not-found or other error
|
|
# condition. This is sufficient to atomically switch the current link
|
|
# tree.
|
|
|
|
print "switching $current to $link\n";
|
|
|
|
my $tmplink = "$linkdir/new_current";
|
|
symlink($link, $tmplink) or die "cannot create $tmplink";
|
|
rename($tmplink, $current) or die "cannot rename $tmplink";
|
|
|
|
if (!$keep && defined $oldlink) {
|
|
print "deleting old $oldlink\n";
|
|
unlink($oldlink) == 1 || print "cannot delete $oldlink\n";
|
|
unlink("$oldlink.hash") == 1 || print "cannot delete $oldlink.hash\n";
|
|
}
|