when you say "if one exists" does that mean that from the url 'http://peeron.com/inv' you don't want to get anything? Or do you want to get 'peeron.com'? or maybe '66.216.39.12'?

for the simplest case, you just want to get the ip from a url like 'http://66.216.39.12/inv'. A simple regex to do this would be:

$url = "http://66.216.39.12/inv";
$url =~ m!https?://((?:\d{1,3}\.){3}\d{1,3})!i;
$ip = $1;
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of course, this will also match things like "http://999.999.999.999/", but I'm not going to worry about that.

For the more complex case, where you actually want the real ip, given the hostname, I'd use Net::DNS. Shamelessly copied from the Net::DNS manpage

use Net::DNS;

my $url = "http://peeron.com/inv";
$url =~ m!https?://([^/]+)!i;

my $res   = Net::DNS::Resolver->new;
my $query = $res->search($1);
  
if ($query) {
    foreach my $rr ($query->answer) {
        next unless $rr->type eq "A";
        print $rr->address, "\n";
    }
} else {
    print "query failed: ", $res->errorstring, "\n";
}
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Again, the usual warnings - this assumes you have a valid URI, and not something that will buffer overflow your DNS server, for example.

update: or look below at rob_au's reply, for the really clean solution.

-- Dan

Sorry I didn't explain it very well. If I have a URL such as http://www.somedomain.com/this_page.html I don't want to do anything. On the other hand, if I have a URL such as http://10.1.1.1/this_dir/this_page.html I wish to extract the IP address which in this case would be 10.1.1.1.

Looks like your first solution just might do the trick!

Thanks much!

Hrmmm, in light of this clarification, I think something like the following may be best ...

use Socket;
use URI;

my $url = 'http://www.mydomain.com';

my $uri = URI->new( $url );
my $ip_addr = gethostbyname( $uri->host );
$ip_addr = inet_ntoa( $ip_addr );

if ( $uri->host eq $ip_addr ) {

    #... Creatures evolve, code does stuff

}
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The advantage that this method of employing the URI module over a simple regular expression is the correct handling of more complex URLs (which may incorporate username and password authentication details in the form of scheme://username:password@host:port/) and validation of IP addresses.

 

perl -e 'print+unpack("N",pack("B32","00000000000000000000000111001001")),"\n"'

Given a textual URL (protocol://host.dom/dir/file), the first thing you'll need to do is extract the "host.dom" part from the entire URL.   A CPAN search on "url" turns up some hits on modules that may (or may not) help.   Next you'd need to resolve the host names to IP addresses using DNS.   A quick look through Networking Code in Code Catacombs finds (code) Resolve list of DNS names by yours truly that should do nicely.

use Socket;
use URI;

my $url = 'http://www.mydomain.com';

my $uri = URI->new( $url );
my $ip_addr = gethostbyname( $uri->host );

print $url, " -> ", inet_ntoa( $ip_addr ), "\n";
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perl -e 'print+unpack("N",pack("B32","00000000000000000000000111001000")),"\n"'