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#! /usr/bin/perl -w
use strict;
my $pkglist = $ENV{"NIX_ACTIVATIONS"};
$pkglist or die "NIX_ACTIVATIONS not set";
my $linkdir = $ENV{"NIX_LINKS"};
$linkdir or die "NIX_LINKS not set";
my @dirs = ("bin", "sbin", "lib");
# Figure out a generation number.
my $nr = 1;
while (-e "$linkdir/$nr") { $nr++; }
my $gendir = "$linkdir/$nr";
print "populating $gendir\n";
# Create the subdirectories.
mkdir $gendir;
foreach my $dir (@dirs) {
mkdir "$gendir/$dir";
}
# For each activated package, create symlinks.
sub createLinks {
my $srcdir = shift;
my $dstdir = shift;
my @srcfiles = glob("$srcdir/*");
foreach my $srcfile (@srcfiles) {
my $basename = $srcfile;
$basename =~ s/^.*\///g; # strip directory
my $dstfile = "$dstdir/$basename";
if (-d $srcfile) {
# !!! hack for resolving name clashes
if (!-e $dstfile) {
mkdir($dstfile) or
die "error creating directory $dstfile";
}
-d $dstfile or die "$dstfile is not a directory";
createLinks($srcfile, $dstfile);
} else {
print "linking $dstfile to $srcfile\n";
symlink($srcfile, $dstfile) or
die "error creating link $dstfile";
}
}
}
open PKGS, "< $pkglist";
while (<PKGS>) {
chomp;
my $hash = $_;
my $pkgdir = `nix getpkg $hash`;
if ($?) { die "`nix getpkg' failed"; }
chomp $pkgdir;
print "merging $pkgdir\n";
foreach my $dir (@dirs) {
createLinks("$pkgdir/$dir", "$gendir/$dir");
}
}
close PKGS;
# Make $gendir 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.
my $current = "$linkdir/current";
print "switching $current to $gendir\n";
my $tmplink = "$linkdir/new_current";
symlink($gendir, $tmplink) or die "cannot create $tmplink";
rename($tmplink, $current) or die "cannot rename $tmplink";
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