Net::netent(3)

NNAAMMEE
       Net::netent - by-name interface to Perl's built-in
       getnet*() functions

SSYYNNOOPPSSIISS
        use Net::netent qw(:FIELDS);
        getnetbyname("loopback")               or die "bad net";
        printf "%s is %08X\n", $n_name, $n_net;

        use Net::netent;

        $n = getnetbyname("loopback")          or die "bad net";
        { # there's gotta be a better way, eh?
            @bytes = unpack("C4", pack("N", $n->net));
            shift @bytes while @bytes && $bytes[0] == 0;
        }
        printf "%s is %08X [%d.%d.%d.%d]\n", $n->name, $n->net, @bytes;

DDEESSCCRRIIPPTTIIOONN
       This module's default exports override the core
       getnetbyname() and getnetbyaddr() functions, replacing
       them with versions that return "Net::netent" objects.
       This object has methods that return the similarly named
       structure field name from the C's netent structure from
       netdb.h; namely name, aliases, addrtype, and net.  The
       aliases method returns an array reference, the rest
       scalars.

       You may also import all the structure fields directly into
       your namespace as regular variables using the :FIELDS
       import tag.  (Note that this still overrides your core
       functions.)  Access these fields as variables named with a
       preceding n_.  Thus, $net_obj->name() corresponds to
       $n_name if you import the fields.  Array references are
       available as regular array variables, so for example @{
       $net_obj->aliases() } would be simply @n_aliases.

       The getnet() funtion is a simple front-end that forwards a
       numeric argument to getnetbyaddr(), and the rest to
       getnetbyname().

       To access this functionality without the core overrides,
       pass the use an empty import list, and then access
       function functions with their full qualified names.  On
       the other hand, the built-ins are still available via the
       CORE:: pseudo-package.

EEXXAAMMPPLLEESS
       The getnet() functions do this in the Perl core:

           sv_setiv(sv, (I32)nent->n_net);

       The gethost() functions do this in the Perl core:

           sv_setpvn(sv, hent->h_addr, len);

       That means that the address comes back in binary for the
       host functions, and as a regular perl integer for the net
       ones.  This seems a bug, but here's how to deal with it:

        use strict;
        use Socket;
        use Net::netent;

        @ARGV = ('loopback') unless @ARGV;

        my($n, $net);

        for $net ( @ARGV ) {

            unless ($n = getnetbyname($net)) {
               warn "$0: no such net: $net\n";
               next;
            }

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

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

            # this is stupid; first, why is this not in binary?
            # second, why am i going through these convolutions
            # to make it looks right
            {
               my @a = unpack("C4", pack("N", $n->net));
               shift @a while @a && $a[0] == 0;
               printf "\taddr is %s [%d.%d.%d.%d]\n", $n->net, @a;
            }

            if ($n = getnetbyaddr($n->net)) {
               if (lc($n->name) ne lc($net)) {
                   printf "\tThat addr reverses to net %s!\n", $n->name;
                   $net = $n->name;
                   redo;
               }
            }
        }

NNOOTTEE
       While this class is currently implemented using the
       Class::Struct module to build a struct-like class, you
       shouldn't rely upon this.

AAUUTTHHOORR
       Tom Christiansen