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

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

	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 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.

       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";

	    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	shouldn't rely upon this.

       Tom Christiansen

perl v5.26.0			  2017-02-28			Net::netent(3)


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