Ping or die

So, we've got this computer that we use as a router... and since it probably eats electricity like crazy, compared to an ordinary router, every night when everyone goes off-line somebody has to turn it off. And since programmers are lazy, we've been kicking around the idea of making a program that turns the damn thing off by itself.

But since programmers are lazy, I only did it today, after a year of excuse finding (at which I am highly proficient).

Result: here's a little Perl script to run commands when some computers go off-line. It turned out quite simple. Enjoy!

1 #!/usr/bin/perl 
2 #
3 # Ping or die
4 #
5 # Pings all ip addresses and turns off the machine when 
6 # all of them are dead.
7 # If you need to run other commads, you can do that too. 
8 #
9 # Parameters:
10#   c - command to run,
11#   s - sleep time between pinging (in seconds),
12#   t - ping timeout (in seconds),
13#   IP addresses or hostnames to watch.
14# Example:
15#   Turn on the Rokudan when the router's down for a minute:
16#       ping_or_die -s 60 "mpg321 Rokudan.mp3" 10.0.0.2
17# Author:
18#   Konrad Siek
19
20# Packages
21use Net::Ping;
22use Getopt::Std;
23
24# Defaults
25my $command = "shutdown -h now";
26my $sleep_time = 300;
27my $timeout = 10;
28my $hosts = ();
29
30# Setup options
31my %options = ();
32getopt "cst", \%options;
33$command = @options{c} if defined @options{c};
34$sleep_time = @options{s} if defined @options{s};
35$timeout = @options{t} if defined @options{t};
36@hosts = @ARGV;
37
38# If no hosts were provided print help and exit.
39if (scalar @hosts < 1) {
40    print "Usage: $0 [options] list-of-ips\n";
41    print "\t-c\tcommand to run\n";
42    print "\t-s\tsleep time between pinging (in seconds)\n";
43    print "\t-t\tping timeout (in seconds)\n";    
44    exit -1;
45}
46
47# Setup ping - 30 second timeout
48$ping = Net::Ping->new("tcp", $timeout);
49
50# Main program
51my $again;
52do {
53    $again = 0;
54    # Wait some time before checking
55    sleep $sleep_time;
56    # Ping machines
57    foreach (@hosts) {
58        my $present = $ping->ping($_);
59        $again |= $present;
60    }
61} while ($again);
62
63# Finish up ping
64$ping->close();
65
66# Info
67print "$0: dead hosts: @hosts\n";
68print "$0: running command '$command'\n";
69
70# Run command
71system $command;
72

The code is also available at GitHub as perl/ping_or_die.