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# Net::Domain.pm
#
# Copyright (C) 1995-1998 Graham Barr. All rights reserved.
# Copyright (C) 2013-2014, 2020 Steve Hay. All rights reserved.
# This module is free software; you can redistribute it and/or modify it under
# the same terms as Perl itself, i.e. under the terms of either the GNU General
# Public License or the Artistic License, as specified in the F<LICENCE> file.
package Net::Domain;
use 5.008001;
use strict;
use warnings;
use Carp;
use Exporter;
use Net::Config;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw(hostname hostdomain hostfqdn domainname);
our $VERSION = "3.15";
my ($host, $domain, $fqdn) = (undef, undef, undef);
# Try every conceivable way to get hostname.
sub _hostname {
# we already know it
return $host
if (defined $host);
if ($^O eq 'MSWin32') {
require Socket;
my ($name, $alias, $type, $len, @addr) = gethostbyname($ENV{'COMPUTERNAME'} || 'localhost');
while (@addr) {
my $a = shift(@addr);
$host = gethostbyaddr($a, Socket::AF_INET());
last if defined $host;
}
if (defined($host) && index($host, '.') > 0) {
$fqdn = $host;
($host, $domain) = $fqdn =~ /^([^.]+)\.(.*)$/;
}
return $host;
}
elsif ($^O eq 'MacOS') {
chomp($host = `hostname`);
}
elsif ($^O eq 'VMS') { ## multiple varieties of net s/w makes this hard
$host = $ENV{'UCX$INET_HOST'} if defined($ENV{'UCX$INET_HOST'});
$host = $ENV{'MULTINET_HOST_NAME'} if defined($ENV{'MULTINET_HOST_NAME'});
if (index($host, '.') > 0) {
$fqdn = $host;
($host, $domain) = $fqdn =~ /^([^.]+)\.(.*)$/;
}
return $host;
}
else {
local $SIG{'__DIE__'};
# syscall is preferred since it avoids tainting problems
eval {
my $tmp = "\0" x 256; ## preload scalar
eval {
package main;
require "syscall.ph"; ## no critic (Modules::RequireBarewordIncludes)
defined(&main::SYS_gethostname);
}
|| eval {
package main;
require "sys/syscall.ph"; ## no critic (Modules::RequireBarewordIncludes)
defined(&main::SYS_gethostname);
}
and $host =
(syscall(&main::SYS_gethostname, $tmp, 256) == 0)
? $tmp
: undef;
}
# POSIX
|| eval {
require POSIX;
$host = (POSIX::uname())[1];
}
# trusty old hostname command
|| eval {
chop($host = `(hostname) 2>/dev/null`); # BSD'ish
}
# sysV/POSIX uname command (may truncate)
|| eval {
chop($host = `uname -n 2>/dev/null`); ## SYSV'ish && POSIX'ish
}
# Apollo pre-SR10
|| eval { $host = (split(/[:. ]/, `/com/host`, 6))[0]; }
|| eval { $host = ""; };
}
# remove garbage
$host =~ s/[\0\r\n]+//go;
$host =~ s/(\A\.+|\.+\Z)//go;
$host =~ s/\.\.+/\./go;
$host;
}
sub _hostdomain {
# we already know it
return $domain
if (defined $domain);
local $SIG{'__DIE__'};
return $domain = $NetConfig{'inet_domain'}
if defined $NetConfig{'inet_domain'};
# try looking in /etc/resolv.conf
# putting this here and assuming that it is correct, eliminates
# calls to gethostbyname, and therefore DNS lookups. This helps
# those on dialup systems.
local ($_);
if (open(my $res, '<', "/etc/resolv.conf")) {
while (<$res>) {
$domain = $1
if (/\A\s*(?:domain|search)\s+(\S+)/);
}
close($res);
return $domain
if (defined $domain);
}
# just try hostname and system calls
my $host = _hostname();
my (@hosts);
@hosts = ($host, "localhost");
unless (defined($host) && $host =~ /\./) {
my $dom = undef;
eval {
my $tmp = "\0" x 256; ## preload scalar
eval {
package main;
require "syscall.ph"; ## no critic (Modules::RequireBarewordIncludes)
}
|| eval {
package main;
require "sys/syscall.ph"; ## no critic (Modules::RequireBarewordIncludes)
}
and $dom =
(syscall(&main::SYS_getdomainname, $tmp, 256) == 0)
? $tmp
: undef;
};
if ($^O eq 'VMS') {
$dom ||= $ENV{'TCPIP$INET_DOMAIN'}
|| $ENV{'UCX$INET_DOMAIN'};
}
chop($dom = `domainname 2>/dev/null`)
unless (defined $dom || $^O =~ /^(?:cygwin|MSWin32|android)/);
if (defined $dom) {
my @h = ();
$dom =~ s/^\.+//;
while (length($dom)) {
push(@h, "$host.$dom");
$dom =~ s/^[^.]+.+// or last;
}
unshift(@hosts, @h);
}
}
# Attempt to locate FQDN
foreach (grep { defined $_ } @hosts) {
my @info = gethostbyname($_);
next unless @info;
# look at real name & aliases
foreach my $site ($info[0], split(/ /, $info[1])) {
if (rindex($site, ".") > 0) {
# Extract domain from FQDN
($domain = $site) =~ s/\A[^.]+\.//;
return $domain;
}
}
}
# Look for environment variable
$domain ||= $ENV{LOCALDOMAIN} || $ENV{DOMAIN};
if (defined $domain) {
$domain =~ s/[\r\n\0]+//g;
$domain =~ s/(\A\.+|\.+\Z)//g;
$domain =~ s/\.\.+/\./g;
}
$domain;
}
sub domainname {
return $fqdn
if (defined $fqdn);
_hostname();
# *.local names are special on darwin. If we call gethostbyname below, it
# may hang while waiting for another, non-existent computer to respond.
if($^O eq 'darwin' && $host =~ /\.local$/) {
return $host;
}
_hostdomain();
# Assumption: If the host name does not contain a period
# and the domain name does, then assume that they are correct
# this helps to eliminate calls to gethostbyname, and therefore
# eliminate DNS lookups
return $fqdn = $host . "." . $domain
if (defined $host
and defined $domain
and $host !~ /\./
and $domain =~ /\./);
# For hosts that have no name, just an IP address
return $fqdn = $host if defined $host and $host =~ /^\d+(\.\d+){3}$/;
my @host = defined $host ? split(/\./, $host) : ('localhost');
my @domain = defined $domain ? split(/\./, $domain) : ();
my @fqdn = ();
# Determine from @host & @domain the FQDN
my @d = @domain;
LOOP:
while (1) {
my @h = @host;
while (@h) {
my $tmp = join(".", @h, @d);
if ((gethostbyname($tmp))[0]) {
@fqdn = (@h, @d);
$fqdn = $tmp;
last LOOP;
}
pop @h;
}
last unless shift @d;
}
if (@fqdn) {
$host = shift @fqdn;
until ((gethostbyname($host))[0]) {
$host .= "." . shift @fqdn;
}
$domain = join(".", @fqdn);
}
else {
undef $host;
undef $domain;
undef $fqdn;
}
$fqdn;
}
sub hostfqdn { domainname() }
sub hostname {
domainname()
unless (defined $host);
return $host;
}
sub hostdomain {
domainname()
unless (defined $domain);
return $domain;
}
1; # Keep require happy
__END__
=head1 NAME
Net::Domain - Attempt to evaluate the current host's internet name and domain
=head1 SYNOPSIS
use Net::Domain qw(hostname hostfqdn hostdomain domainname);
=head1 DESCRIPTION
Using various methods B<attempt> to find the Fully Qualified Domain Name (FQDN)
of the current host. From this determine the host-name and the host-domain.
Each of the functions will return I<undef> if the FQDN cannot be determined.
=head2 Functions
=over 4
=item C<hostfqdn()>
Identify and return the FQDN of the current host.
=item C<domainname()>
An alias for hostfqdn().
=item C<hostname()>
Returns the smallest part of the FQDN which can be used to identify the host.
=item C<hostdomain()>
Returns the remainder of the FQDN after the I<hostname> has been removed.
=back
=head1 EXPORTS
The following symbols are, or can be, exported by this module:
=over 4
=item Default Exports
I<None>.
=item Optional Exports
C<hostname>,
C<hostdomain>,
C<hostfqdn>,
C<domainname>.
=item Export Tags
I<None>.
=back
=head1 KNOWN BUGS
See L<https://rt.cpan.org/Dist/Display.html?Status=Active&Queue=libnet>.
=head1 AUTHOR
Graham Barr E<lt>L<gbarr@pobox.com|mailto:gbarr@pobox.com>E<gt>.
Adapted from Sys::Hostname by David Sundstrom
E<lt>L<sunds@asictest.sc.ti.com|mailto:sunds@asictest.sc.ti.com>E<gt>.
Steve Hay E<lt>L<shay@cpan.org|mailto:shay@cpan.org>E<gt> is now maintaining
libnet as of version 1.22_02.
=head1 COPYRIGHT
Copyright (C) 1995-1998 Graham Barr. All rights reserved.
Copyright (C) 2013-2014, 2020 Steve Hay. All rights reserved.
=head1 LICENCE
This module is free software; you can redistribute it and/or modify it under the
same terms as Perl itself, i.e. under the terms of either the GNU General Public
License or the Artistic License, as specified in the F<LICENCE> file.
=head1 VERSION
Version 3.15
=head1 DATE
20 March 2023
=head1 HISTORY
See the F<Changes> file.
=cut