I like to know when and for how long my ADSL line is down. Sadly, I can't do any SNMP goodness, so I wrote a little perl script which runs every five minutes from a cron job. It tries to ping my ISP's nameserver and records the result. It also emails me whenever the line goes down, when it comes back up, and whenever there's packet loss.

#!/usr/local/bin/perl

use warnings;
use strict;

use GDBM_File;
use Fcntl qw(O_CREAT O_RDWR);
use Mail::Mailer;

tie my %history, 'GDBM_File', "$ENV{HOME}/pinger/history", O_CREAT|O_R
+DWR, 0600;

my $ping=`ping -c 5 195.112.4.4|grep received`;
$ping =~ /(\d+)%/; my $packet_loss = $1;
chomp($packet_loss);

if($packet_loss != 0) { $history{time()} = $packet_loss; }

if(!defined($history{prev_state})) {
        $history{prev_state}=100;
        $history{most_recent} = time;
}

if($packet_loss == 100 && $history{prev_state} != 100) { # connection 
+gone down
        email(
                "Connection died at ".scalar(localtime)
        );
        $history{prev_state} = $packet_loss;
        $history{most_recent} = time;
} elsif($history{prev_state} == 100) {               # previous was 10
+0% loss
        if($packet_loss != 100) {                     # ... and we're 
+back up
                email(
                        "Connection came back up with $packet_loss% pa
+cket\n".
                        "loss at ".scalar(localtime).".\n\n".
                        "It went down at ".
                        scalar(localtime($history{most_recent}))
                );
                $history{prev_state} = $packet_loss;
                $history{most_recent} = time;
        }
} elsif($history{prev_state} == 0) {                 # previous was 0%
+ loss
        if($packet_loss != 0) {                       # ... now we hav
+e lossage
                email("$packet_loss% packet loss on connection at ".sc
+alar(local
time));
                $history{prev_state} = $packet_loss;
                $history{most_recent} = time;
        }
}

sub email {
        my $body=shift;
        my $mailer=new Mail::Mailer;
        $mailer->open({
                To      => 'david@cantrell.org.uk',
                Subject => 'LINEMONITOR report from '.`hostname`
        });
        print $mailer $body;
        $mailer->close;
}
[download]

There's also another script which shows me the log:

#!/usr/local/bin/perl

use warnings;
use strict;

use GDBM_File;
use Fcntl qw(O_CREAT O_RDWR);
use Data::Dumper;

tie my %history, 'GDBM_File', "$ENV{HOME}/pinger/history", O_CREAT|O_R
+DWR, 0600;

print "Loss%\tTime\n";
foreach my $key (sort { $a <=> $b } grep { /^\d+$/ } keys %history) {
        print "$history{$key}\t".scalar(localtime($key))."\n";
}
[download]