use Net::hostent;
        use Socket;

        @ARGV = ('netscape.com') unless @ARGV;

        for $host ( @ARGV ) {

           unless ($h = gethost($host)) {
               warn "$0: no such host: $host\n";
               next;
           }

           printf "\n%s is %s%s\n",
                   $host,
                   lc($h->name) eq lc($host) ? "" : "*really* ",
                   $h->name;

           print "\taliases are ", join(", ", @{$h->aliases}), "\n"
                       if @{$h->aliases};

           if ( @{$h->addr_list} > 1 ) {
               my $i;
               for $addr ( @{$h->addr_list} ) {
                   printf "\taddr #%d is [%s]\n", $i++, inet_ntoa($add
+r);
               }
           } else {
               printf "\taddress is [%s]\n", inet_ntoa($h->addr);
           }

           if ($h = gethostbyaddr($h->addr)) {
               if (lc($h->name) ne lc($host)) {
                   printf "\tThat addr reverses to host %s!\n", $h->na
+me;
                   $host = $h->name;
                   redo;
               }
           }
        }
[download]

-Mark

And then there are wildcard DNS records. Try the above code (assuming the script is called "resolve") with:

$ perl resolve www.startpagina.nl
[download]

which gives:

www.startpagina.nl is www.startpagina.nl
        addr #0 is [62.69.162.8]
        addr #1 is [62.69.162.6]
        addr #2 is [62.69.162.7]
[download]

All nice and good, you would say. You get 3 IP-numbers and it resolves back correctly. Now you want to find all the aliases to "www.startpagina.nl". Try this by doing:

$ perl resolve anythingyoucanthinkof.startpagina.nl
[download]

which generates this output:

anythingyoucanthinkof.startpagina.nl is anythingyoucanthinkof.startpag
+ina.nl
        addr #0 is [62.69.162.7]
        addr #1 is [62.69.162.8]
        addr #2 is [62.69.162.6]
        That addr reverses to host www.startpagina.nl!

www.startpagina.nl is www.startpagina.nl
        addr #0 is [62.69.162.8]
        addr #1 is [62.69.162.6]
        addr #2 is [62.69.162.7]
[download]

Now replace "anythingyoucanthinkof" with anything else you can think of. Then meditate on the number of aliases "www.startpagina.nl" has. ;-)

Hope this helps.

Liz

Thanks for all the pointers - now understand a lot more about how to properly use Net::hostent. However, my problem still remains. For instance, if I use the code snippet supplied my shenme, I get exactly the output promised. But my problem is that I would like to be able to give 'a562.cd.akamai.net' as the argument and have it return 'www.microsoft.com' as an alias. Alas, this does not happen and it appears that this is indeed the way this module (Net::hostent) is intended to work. So I am still wandering in the dark :( Thanks for all your efforts - Mark

Works for me, along with the original gethostbyname().

use Net::hostent;
    my  $h = gethost( 'www.microsoft.com' );
    #       name  aliases  addrtype  length  addr_list
    my  @aliases = @{ $h->aliases };

    printf "  Name  '%s'\n", $h->name;
    printf "  Aliases are '%s'\n", join("', '", @aliases );
[download]

Output:

  Name  'a562.cd.akamai.net'
  Aliases are 'www.microsoft.com', 'www.microsoft.com.edgesuite.net'

1. A hostname A can give you an IP-number if it resolves.
2. A reverse lookup of the IP-number may give you a hostname B if it resolves.
3. A and B may or may not be the same.

You should think of hostnames as nothing other than a "roadmap" to get to a specific (IP) address. And there are an infinite number of ways to Rome: some of them are described (have a hostname) and some are not described. But you will never be able to find them all, unless someone (else) tells them to you.

Hope this helps.

Liz