Beefy Boxes and Bandwidth Generously Provided by pair Networks
We don't bite newbies here... much


by root (Scribe)
on Dec 23, 1999 at 00:52 UTC ( #1231=perlfunc: print w/replies, xml ) Need Help??


See the current Perl documentation for Net::netent.

Here is our local, out-dated (pre-5.6) version:

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

 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&qu

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() funtion 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.


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: $net\n";
     printf "\n%s is %s%s\n", 
            lc($n->name) eq lc($net) ? "" : "*really* ",
     print "\taliases are ", join(", ", @{$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;


While this class is currently implemented using the Class::Struct module to build a struct-like class, you shouldn't rely upon this.


Tom Christiansen

Log In?

What's my password?
Create A New User
Corion idly wonders about creating a series of HTTP requests. There seems to be no framework to generate a series of HTTP requests, like "try all these requests"
[Corion]: This is vaguely inspired by that list of "nasty" strings, which I'd like to replace among HTTP parameters, just to see whether the application crashes, but also for easy downloading of a list of URLs etc
[Corion]: Maybe I'll just conoct something using Algorithm::Permute to create an (OO) generator for such requests, or a simple function.
[Corion]: For testing I imagine one would want to test a random sampling of such "bad"/"unexpected" requests, while for downloading, one would want to generate them all in order, but not necessarily as a huge list

How do I use this? | Other CB clients
Other Users?
Others drinking their drinks and smoking their pipes about the Monastery: (9)
As of 2017-01-16 15:40 GMT
Find Nodes?
    Voting Booth?
    Do you watch meteor showers?

    Results (151 votes). Check out past polls.