Net::netent(3pm)                                Perl Programmers Reference Guide                                Net::netent(3pm)



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

SYNOPSIS
        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;

DESCRIPTION
       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() function 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.

EXAMPLES
       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;
               }
            }
        }

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

AUTHOR
       Tom Christiansen



perl v5.12.4                                               2011-06-01                                           Net::netent(3pm)