Net::netent(3perl)

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

okay bestie, welcome to Net::netent, straight out of the Perl Programmers Reference Guide ✨ this is the lil module that makes your network lookups return actual objects instead of boring ol' lists. it's giving glow-up, it's giving structure. let's get into it 🫶

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✨ NAME ✨

Net::netent — a by-name interface to Perl's built-in getnet*() functions, no cap 🎀

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🌸 SYNOPSIS 🌸

here's the vibe, two whole ways to do the thing:

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;

like. pick your fighter 💅 either you import the fields and get cute lil variables, or you go full object mode with ->. both eat, honestly 🔥

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💜 DESCRIPTION 💜

so here's the tea, bestie ☕ this module's default exports straight-up override the core getnetbyname() and getnetbyaddr() functions, swapping them out for versions that hand you back "Net::netent" objects instead. iconic behavior tbh 👑

that 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. and listen: the aliases method returns an array reference, while the rest return scalars. one of these things is not like the other 🙈

you can also import all the structure fields directly into your namespace as regular variables using the :FIELDS import tag. (heads up tho — this still overrides your core functions, so don't act surprised 😭)

access these fields as variables named with a preceding n_. so like, "$net_obj->name()" corresponds to $n_name if you import the fields. array references are available as regular array variables too, so for example "@{ $net_obj->aliases() }" would simply be @n_aliases. the way that just works ✨

the getnet() function is a simple front-end that forwards a numeric argument to getnetbyaddr(), and the rest to getnetbyname(). it's basically the receptionist of this whole operation 🎀

and if you wanna access this functionality without the core overrides? pass the "use" an empty import list, and then access function functions with their full qualified names. (yes, "function functions", that's what it says, i don't make the rules 🫠) on the other hand, the built-ins are still available via the "CORE::" pseudo-package. safe and sound 🧚

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🌈 EXAMPLES 🌈

okay so, the getnet() functions do this in the Perl core:

sv_setiv(sv, (I32)nent->n_net);

and the gethost() functions do this in the Perl core:

sv_setpvn(sv, hent->h_addr, len);

which means 👀 the address comes back in binary for the host functions, and as a regular perl integer for the net ones. yeah. that 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;
       }
    }
}

slay. it even reverse-lookups and loops back around with redo, main character energy fr fr 💅

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🦋 NOTE 🦋

while this class is currently implemented using the Class::Struct module to build a struct-like class, you shouldn't rely upon this. it's giving "internal implementation detail", so don't go building your whole personality on it bestie 😭

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👑 AUTHOR 👑

Tom Christiansen — the icon, the legend, the moment ⭐

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and that's the whole page, pookie 🫶 this was Net::netent(3perl) from perl v5.44.0, dated 2026-10-17 — write that down, cite it in your notes, be that girl 💖✨🎀