Greetings, Oh Most Monkly of Monks! :-)

My quest to produce a script which will give me a sorted list of hosts pinged is coming along nicely, thanks to some people here who pointed me in the right direction to find the information I needed to get started. All was going along pretty well, until I decided to Get Clever and have it return the hostname of an IP being pinged. That's when it Got Interesting. :-) Now when I try to run the script, I get:

Use of uninitialized value in printf at ./pingit.pl line 33.

Line 33 is the printf line which says the host is alive. Here's the script so far:

#!/usr/bin/perl -w
#
# Ping a range of IP addresses, and list sorted by ping time.
#
# This uses the ICMP echo method instead of UDP echo, as
# some routers don't pass UDP echo.  Also, if the remote host
# doesn't have an appropriate service listening on the UDP
# echo port, it won't answer.
#
# D. Guntner, 21-July-2007
# Ver 1.0, 21-July-2007

use Net::Ping;
use Net::Netmask;

die "I need root privs to run, dude.\n" unless $> == 0;

# Get the IP address(es)
my $netaddr = shift(@ARGV);
usage() unless $netaddr;   # Give usage message if no input

my $hostname="";
my $block = new Net::Netmask($netaddr);
my @hosts = $block->enumerate();

my $p = Net::Ping->new("icmp");
$p->hires();   # Comment out this line if no Time::HiRes installed
               # (Or better yet, install Time::HiRes... :-) )

foreach $host (@hosts) {
  ($ret, $duration, $ip) = $p->ping($host, 5.5);
  if ($ret) {
    printf("%s [ip: $ip] is alive  %.2f ms)\n", gethostbyip($host), 10
+00 * $duration);
  }
}
$p->close();

sub gethostbyip {
  use Socket;
  
  my $hostip = @_ ;
  my $iaddr = inet_aton($hostip);
  my $hostname = gethostbyaddr($iaddr, AF_INET);
  return $hostname;
}

sub usage {
  use File::Basename;
  
  my $progname = basename($0);
  
  print <<"EO_USAGE";
This script will ping scan a range if IP addresses, and return
a list sorted by ping time.  Give address in CIDR format.

   Usage:    $progname {IP/NETMASK}
   Example:  $progname 1.2.3.4/24

You *could* put in only a single IP address, but there wouldn't
be much point to that, now would there? :-)
EO_USAGE
  exit;
}
[download]

No, it's not actually doing the sort yet. :-) I'm still making sure it pings all hosts and returns the right values. I *could* do without the host names if I had to, but it would be nice to have them. I'm at a loss as to what value is uninitialized, however. It doesn't seem to matter if I put "1.2.3.4" as an address or "1.2.3.4/24" (just as an example - I'm not actually using those as input when I run this) as one; the error message keeps coming up. Anyone know what it might be talking about?

--Dave