#!/usr/bin/perl

my $menu = "/boot/grub/menu.lst";
my $once = "/boot/grub/menu.once";

open F, $menu or die "grub is not installed ($menu is missing)\n";
my @entries = map { /\s(\S.*)/ } grep { /^title\s/ } my @l = <F>;

grep { m|^altconfigfile\s.*grub/menu\.once| } @l or die "rebootin is of no use without altconfigfile\n";
@entries > 0 or die "bad menu.lst (no entry found)\n";
@ARGV == 1 or usage();

for (my $i = 0; $i < @entries; $i++) { 
    $ARGV[0] eq $entries[$i] and set($i);
}

print STDERR "$ARGV[0] not found\n";
usage(); # not found

sub set {
    open F, ">$once" or die "can't write rebootin file ($once), verify the rights\n";
    print F "default $_[0]\ntimeout 0\n";
    exec "reboot";
}

sub usage {
    die "usage: rebootin <label>\n  where <label> is one of " . join(", ", @entries) . "\n";
}