GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  -  NET::NETENT (3)

.ds Aq ’

NAME

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

CONTENTS

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";
 { # theres 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
Search for    or go to Top of page |  Section 3 |  Main Index


perl v5.22.1 NET::NETENT (3) 2015-10-17

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.