# 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 $VERSION = "3.13"; my ($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 3.13 =head1 DATE 23 Dec 2020 =head1 HISTORY See the F<Changes> file. =cut