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 
21 use Net::Ping;
22 use Getopt::Std;
23  
24 # Defaults 
25 my $command = "shutdown -h now";
26 my $sleep_time = 300;
27 my $timeout = 10;
28 my $hosts = ();
29  
30 # Setup options 
31 my %options = ();
32 getopt "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. 
39 if (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 
51 my $again;
52 do {
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 
67 print "$0: dead hosts: @hosts\n";
68 print "$0: running command '$command'\n";
69  
70 # Run command 
71 system $command;
72  

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