Net::netent(3p) Perl Programmers Reference Guide Net::netent(3p) #
Net::netent(3p) Perl Programmers Reference Guide Net::netent(3p)
NNAAMMEE #
Net::netent - by-name interface to Perl's built-in getnet*() functions
SSYYNNOOPPSSIISS #
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, $n->net, @bytes;
DDEESSCCRRIIPPTTIIOONN #
This module's default exports override the core ggeettnneettbbyynnaammee(()) and
ggeettnneettbbyyaaddddrr(()) functions, replacing them with versions that return
"Net::netent" objects. This object has methods that return the similarly
named structure field name from the C's netent structure from _n_e_t_d_b_._h;
namely name, aliases, addrtype, and net. The aliases method returns an
array reference, the rest scalars.
You may also import all the structure fields directly into your namespace
as regular variables using the :FIELDS import tag. (Note that this still
overrides your core functions.) Access these fields as variables named
with a preceding "n_". Thus, "$net_obj->name()" corresponds to $n_name
if you import the fields. Array references are available as regular
array variables, so for example "@{ $net_obj->aliases() }" would be
simply @n_aliases.
The ggeettnneett(()) function is a simple front-end that forwards a numeric
argument to ggeettnneettbbyyaaddddrr(()), and the rest to ggeettnneettbbyynnaammee(()).
To access this functionality without the core overrides, pass the "use"
an empty import list, and then access function functions with their full
qualified names. On the other hand, the built-ins are still available
via the "CORE::" pseudo-package.
EEXXAAMMPPLLEESS #
The ggeettnneett(()) functions do this in the Perl core:
sv_setiv(sv, (I32)nent->n_net);
The ggeetthhoosstt(()) functions do this in the Perl core:
sv_setpvn(sv, hent->h_addr, len);
That means that the address comes back in binary for the host functions,
and as a regular perl integer for the net ones. This seems a bug, but
here's how to deal with it:
use strict;
use Socket;
use Net::netent;
@ARGV = ('loopback') unless @ARGV;
my($n, $net);
for $net ( @ARGV ) {
unless ($n = getnetbyname($net)) {
warn "$0: no such net: $net\n";
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;
}
}
}
NNOOTTEE #
While this class is currently implemented using the Class::Struct module
to build a struct-like class, you shouldn't rely upon this.
AAUUTTHHOORR #
Tom Christiansen
perl v5.36.3 2019-02-13 Net::netent(3p)