#!/usr/bin/perl
#
# Copyright (c) 2011 Mathieu Roy <yeupou@gnu.org>
#
#   This program is free software; you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation; either version 2 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
#   USA
#
# Counter part of both if-up.d/prepmountnfs
# Actually, only clean up /etc/fstab. It won't umount the NFS shares. Yeah
# I know that unmounted NFS shares mess up the system, but that's too much
# work just to figure out if the current if-down relates to the interface
# that provides access to the server. And we would not want to loose NFS
# share each time wlan goes down while eth is still up. 

use strict;

my $debug = 0;

use File::Copy;
use File::Temp qw(tempfile tempdir); 

# Create a (secure) temporary file
my ($tempfilefh, $tempfile) = tempfile(UNLINK => 1);

open(FSTAB, "< /etc/fstab");
my $count = 0;
my $skip_next_line = 0;
while (<FSTAB>) {
    # skip this line the previous was a backup
    if ($skip_next_line > 0) {
	print "DBG: skip: $_" if $debug;
	$skip_next_line = 0;
	next;
    }

    # find previously backed-up lines, revert the changes
    if (s/^#CLEVERNFSS###//g) {
	$count++;
	$skip_next_line = 1 
    }
    print $tempfilefh $_;
}
close(FSTAB);
close($tempfilefh);

print "DBG: $count line(s) modified in /etc/fstab\n" if $debug;
exit if $count < 1;

# replace fstab with the (readable to everybody) temporary file
# (obviously, must be root to do so)
system("chmod", "a+r", $tempfile);
move($tempfile, "/etc/fstab")
    or die "unable to overwrite /etc/fstab, are you root? Exit";
print "DBG: /etc/fstab overwrote by $tempfile\n" if $debug;

# EOF