package Sys::Hostname;

use strict;

use Carp;

require Exporter;

our @ISA = qw/ Exporter /;
our @EXPORT = qw/ hostname /;

our $VERSION;

our $host;

BEGIN {
$VERSION = '1.17';
{
local $SIG{__DIE__};
eval {
require XSLoader;
XSLoader::load();
};
warn $@ if $@;
}
}


sub hostname {

# method 1 - we already know it
return $host if defined $host;

# method 1' - try to ask the system
$host = ghname() if defined &ghname;
return $host if defined $host;

if ($^O eq 'VMS') {

# method 2 - no sockets ==> return DECnet node name
eval { local $SIG{__DIE__}; $host = (gethostbyname('me'))[0] };
if ($@) { return $host = $ENV{'SYS$NODE'}; }

# method 3 - has someone else done the job already? It's common for the
# TCP/IP stack to advertise the hostname via a logical name. (Are
# there any other logicals which TCP/IP stacks use for the host name?)
$host = $ENV{'ARPANET_HOST_NAME'} || $ENV{'INTERNET_HOST_NAME'} ||
$ENV{'MULTINET_HOST_NAME'} || $ENV{'UCX$INET_HOST'} ||
$ENV{'TCPWARE_DOMAINNAME'} || $ENV{'NEWS_ADDRESS'};
return $host if $host;

# method 4 - does hostname happen to work?
my($rslt) = `hostname`;
if ($rslt !~ /IVVERB/) { ($host) = $rslt =~ /^(\S+)/; }
return $host if $host;

# rats!
$host = '';
croak "Cannot get host name of local machine";

}
elsif ($^O eq 'MSWin32') {
($host) = gethostbyname('localhost');
chomp($host = `hostname 2> NUL`) unless defined $host;
return $host;
}
else { # Unix
# is anyone going to make it here?

local $ENV{PATH} = '/usr/bin:/bin:/usr/sbin:/sbin'; # Paranoia.

# method 2 - syscall is preferred since it avoids tainting problems
# XXX: is it such a good idea to return hostname untainted?
eval {
local $SIG{__DIE__};
require "syscall.ph";
$host = "\0" x 65; ## preload scalar
syscall(&SYS_gethostname, $host, 65) == 0;
}

# method 2a - syscall using systeminfo instead of gethostname
# -- needed on systems like Solaris
|| eval {
local $SIG{__DIE__};
require "sys/syscall.ph";
require "sys/systeminfo.ph";
$host = "\0" x 65; ## preload scalar
syscall(&SYS_systeminfo, &SI_HOSTNAME, $host, 65) != -1;
}

# method 3 - trusty old hostname command
|| eval {
local $SIG{__DIE__};
local $SIG{CHLD};
$host = `(hostname) 2>/dev/null`; # bsdish
}

# method 4 - use POSIX::uname(), which strictly can't be expected to be
# correct
|| eval {
local $SIG{__DIE__};
require POSIX;
$host = (POSIX::uname())[1];
}

# method 5 - sysV uname command (may truncate)
|| eval {
local $SIG{__DIE__};
$host = `uname -n 2>/dev/null`; ## sysVish
}

# bummer
|| croak "Cannot get host name of local machine";

# remove garbage
$host =~ tr/\0\r\n//d;
$host;
}
}

1;

__END__

=head1 NAME

Sys::Hostname - Try every conceivable way to get hostname

=head1 SYNOPSIS

use Sys::Hostname;
$host = hostname;

=head1 DESCRIPTION

Attempts several methods of getting the system hostname and
then caches the result. It tries the first available of the C
library's gethostname(), C<`$Config{aphostname}`>, uname(2),
C<syscall(SYS_gethostname)>, C<`hostname`>, C<`uname -n`>,
and the file F</com/host>. If all that fails it C<croak>s.

All NULs, returns, and newlines are removed from the result.

=head1 AUTHOR

David Sundstrom E<lt>F<[email protected]>E<gt>

Texas Instruments

XS code added by Greg Bacon E<lt>F<[email protected]>E<gt>

=cut