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The POSIX network-database calls, returning Perl's four-field record of name, aliases, address type and network number.

Version

0.0.9 zef:lizmat

Depends

none beyond the core

License

Artistic-2.0

Its own test suite

2 files, green

Checked

2026-09-15 against Raku++ 3.28.0 and Rakudo 2026.08

Where it lives

raku.land · source

Install it #

$ rakupp install P5getnetbyname

zef install P5getnetbyname writes the same store; either installer leaves the module usable by both engines.

What it is for #

/etc/networks maps names to network numbers the way /etc/hosts maps them to addresses — loopback to 127, and whatever local names an administrator has added. getnetbyname(3) is how a program reads it.

This distribution binds it, along with the reverse lookup and the enumeration, in the shape Perl's getnet* built-ins use.

Reading the database #

/etc/networks is empty or absent on a great many current machines, so an example has to drive off the enumeration and assert shape:

use P5getnetbyname;

setnetent(0);
my @first = getnetent();
endnetent();

if @first {
    say 'record fields  : ', @first.elems;
    say 'name is a Str  : ', @first[0] ~~ Str;
    say 'aliases are a  : ', @first[1].^name;
    say 'addrtype is 2 (AF_INET) : ', @first[2] == 2;
    say 'net is an Int  : ', @first[3] ~~ Int;
}
else {
    say 'this machine has no network database entries';
}
say '';
say 'setnetent : ', setnetent(0);
say 'endnetent : ', endnetent();

record fields  : 4
name is a Str  : True
aliases are a  : Array
addrtype is 2 (AF_INET) : True
net is an Int  : True

setnetent : 1
endnetent : 1

The record is ($name, $aliases, $addrtype, $net). addrtype 2 is AF_INET on both darwin and Linux.

Misses #

use P5getnetbyname;

say 'unknown name   -> ', getnetbyname('nosuchnet-xyzzy').elems, ' fields';
say 'unknown scalar -> ', getnetbyname(Scalar, 'nosuchnet-xyzzy').defined;
say 'bad address    -> ', getnetbyaddr(4294967295, 2).elems, ' fields';
say 'bad addrtype   -> ', getnetbyaddr(127, 99).elems, ' fields';

unknown name   -> 0 fields
unknown scalar -> False
bad address    -> 0 fields
bad addrtype   -> 0 fields

An empty list, never an exception — the convention across the whole P5get* family, and one that makes a miss indistinguishable from the end of an enumeration.

The one thing to know #

The aliases field breaks the family's convention: it is an Array, not a space-joined Str.

use P5getnetbyname;
use P5getprotobyname;
use P5getservbyname;

say 'the same slot, across three siblings:';
say '  P5getprotobyname aliases : ', getprotobyname('tcp')[1].^name;
say '  P5getservbyname  aliases : ', getservbyname('http', 'tcp')[1].^name;

setnetent(0);
my @net = getnetent();
endnetent();
say '  P5getnetbyname   aliases : ', @net ?? @net[1].^name !! 'no entries here';
say '';
say 'so .words — which is right for the other two — silently produces';
say 'an Array\'s gist here rather than the alias names. Use .list.';

the same slot, across three siblings:
  P5getprotobyname aliases : Str
  P5getservbyname  aliases : Str
  P5getnetbyname   aliases : Array

so .words — which is right for the other two — silently produces
an Array's gist here rather than the alias names. Use .list.

P5getgrnam, P5getservbyname and P5getprotobyname all call .join(" ") before putting aliases into the record; this one does not. Code written against a sibling and reused here gets an Array where it expected a string, and the record arity stays 4 either way, so nothing looks wrong.

The scalar forms break the convention too: both of them return the name, where every sibling's scalar-by-name gives an id.

Where the two engines differ #

Nowhere. Every lookup, both scalar forms, the enumeration and all four misses produced identical output on Raku++ and Rakudo.

The thing that will vary is the machine, not the engine. /etc/networks held loopback here, and getnetbyname('localnet') and ('arpanet') — two names that used to be conventional — both returned empty lists. Many current Linux distributions ship the file empty or leave it out entirely, so any code that looks a network up by name needs a fallback for "not present at all".