Learning Perl on Win32 Systems

Chapter 16

1. Here’s one way to do it.

   foreach $host (@ARGV) {
     ($name, $aliases, $addrtype, $length, @addrs) = gethostbyname($host);
     print "$host:\n";
   
     foreach $a (@addrs) {
       print join(".", unpack("C4", $a)), "\n";
     }
   }

   This code just takes a list of machine names, iterates over them, calling get-hostbyname() for each one. We then enumerate each of the addresses, printing them out in dotted decimal notation.

2. Here’s one way to do it:

   use 
                     Win32::Registry;
   $p = shift || die "usage: $0 path";
   # strip leading backslashes
   $p =~ s#^\\##;
   $main::HKEY_LOCAL_MACHINE->Open($p, $key) || 
           die "Open: $!";
   $key->GetValues(\%vals); # get values -hash ref
   foreach $k (keys %vals) {
       $key = $vals{$k};
       print "$$key[0] = $$key[2]\n";
   }

   This code takes a path relative to HKEY_LOCAL_MACHINE (something like SOFTWARE\ActiveWare\Perl5) and strips beginning backslashes, if there are any. It opens the key using the precreated HKEY_LOCAL_MACHINE key. It then calls GetValues (passing it a reference to a hash; see Chapter 18, for more on references). The code then enumerates over the keys of the hash, printing them. Each value consists of a reference to a list with three items, so we assign the list reference to $key. We then have to dereference $key in order to access its values; we do so with the $$key[0] construct.

3. Here’s one way to do it:

   sub CreateKeyPath { my ($subtree, $path) = @_; # break it into components # strip initial path separator, if there is one $path =~ s#^\\##; my (@klist) = split(/\\/, $path); my $key; ...