Net::netent(3) Perl Programmers Reference Guide Net::netent(3)NAMENet::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 @{
$net_obj->aliases() } would be simply @n_aliases.
The getnet() function is a simple front-end that forwards
a numeric argument to getnetbyaddr(), and the rest to
getnetbyname().
To access this functionality without the core overrides,
pass the use an empty import list, and then access
function functions with their full qualified names. On
the other hand, the built-ins are still available via the
CORE:: pseudo-package.
EXAMPLES
The getnet() functions do this in the Perl core:
sv_setiv(sv, (I32)nent->n_net);
The gethost() functions do this in the Perl core:
16/Sep/1999 perl 5.005, patch 03 1
Net::netent(3) Perl Programmers Reference Guide Net::netent(3)
sv_setpvn(sv, hent->h_addr, len);
That means that the address comes back in binary for the
host functions, and as a regular perl integer for the net
ones. This seems a bug, but here's how to deal with it:
use strict;
use Socket;
use Net::netent;
@ARGV = ('loopback') unless @ARGV;
my($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.
16/Sep/1999 perl 5.005, patch 03 2
Net::netent(3) Perl Programmers Reference Guide Net::netent(3)AUTHOR
Tom Christiansen
16/Sep/1999 perl 5.005, patch 03 3