MirBSD manpage: Net::netent(3p)

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


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


      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;


     This module's default exports override the core getnet-
     byname() 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 getnet-

     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::"


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

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

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

     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";

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

          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;


     While this class is currently implemented using the
     Class::Struct module to build a struct-like class, you

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

     shouldn't rely upon this.


     Tom Christiansen

perl v5.8.8                2005-02-05                           3

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