#!/usr/bin/perl

print "===== Flush DNS Cache =====\n";

# The Premise: use sudoedit and other black magic to clear out the memory-
# based disk cache (which is done by writing the number 3 to a certain
# system file)
print "   - Synching file system... ";
`sync`;
print "Done\n";
print "   - Dropping memory disk cache... ";
# - save our current default editor
my $current_editor = $ENV{'EDITOR'};
# - replace default editor with a script that simply clobbers the contents
#   of any file it's handed with the number "3"
$ENV{'EDITOR'} = 'reset_memcache_editor.sh';
# - we now call sudoedit on the system file. How sudoedit works is that it
#   starts by making a temp copy of the system file with appropriate
#   permissions allowing the user to edit. It then passes the path to the
#   temp file to the default editor - typically this would be an interactive
#   editor like 'vi'. However, we've just replaced the editor with a custom
#   script that just writes '3' as the content of the tmp file. Finally, when
#   the editor exits, sudoedit copies the tmp file over the top of the system
#   file, restoring appropriate root-level permissions
`sudoedit /proc/sys/vm/drop_caches`;
# - restore the default editor, just in case something in Greenstone
#   depends on this being a reasonably value
$ENV{'EDITOR'} = $current_editor;
print "Done\n";

# - short break to give OS time to actually notice the drop_caches command
print "   - Waiting for command to complete... ";
sleep(5);
print "Done\n";

print "Complete!\n\n";

exit;