Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

How I can do the reverse nslookup? I am looking for working code as Net::Nslookup doesn't work as advertised for this purpose. I am on linux box, but I cannot make gethostbyaddr to work either. I also tried Net::DNS::Resolver unsuccessfully.

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Re: Reverse nslookup
by ikegami (Patriarch) on Aug 25, 2009 at 20:12 UTC

    In DNS terms, if the ip address is a.b.c.d, you want to lookup the "PTR" (not "A"!) tag for d.c.b.a.in-addr.arpa. That's what gethostbyaddr does: 

    use Socket qw( AF_INET inet_aton );

my $name = gethostbyaddr(inet_aton('69.147.76.15'), AF_INET);
print "$name\n";

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    f1.www.vip.re1.yahoo.com

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      Thank you. It works fine.

      I am also trying to populate a table. Can I use time out?

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Re: Reverse nslookup
by leighsharpe (Monk) on Aug 25, 2009 at 23:40 UTC
    Net::DNS can do reverse lookups. This was taken almost verbatim from the docs: 
    use strict;
use warnings;
use Net::IP;
use Net::DNS;
my $ip = new Net::IP($ARGV[0],4);
print $ip->reverse_ip()."\n";
print "Resolving ...\n";
my $res = Net::DNS::Resolver->new;
my $answer = $res->query($ip->reverse_ip(),'PTR');
my $namer = $answer->{'answer'}[0];
if ($namer->{'ptrdname'}) {
    print "PTR Name: $namer->{'ptrdname'}\n";
} else {
    print "N/A\n";
}

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    Gives: 
    C:\temp>perl revlookup.pl 66.39.54.27
27.54.39.66.in-addr.arpa.
Resolving ...
PTR Name: ads.perlmonks.org

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