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Net::netent(3perl) Perl Programmers Reference Guide Net::netent(3perl)
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
perl v5.20.2 2014-12-27 Net::netent(3perl)
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