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