Net::netent(3)							Net::netent(3)

NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

      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    [Toc]    [Back]

     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.

EXAMPLES    [Toc]    [Back]

     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,



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Net::netent(3)							Net::netent(3)



     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    [Toc]    [Back]

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







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Net::netent(3)							Net::netent(3)



AUTHOR
     Tom Christiansen


									PPPPaaaaggggeeee 3333