


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


NAME
       Net::netent - by-name interface to Perl's built-in get-
       net*() 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 getnetby-
       name() 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 get-
       netbyname().

       To access this functionality without the core overrides,
       pass the "use" an empty import list, and then access func-
       tion 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:




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


           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.





2000-04-06                 perl v5.6.1                          2





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


AUTHOR
       Tom Christiansen























































2000-04-06                 perl v5.6.1                          3


