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package Sys::Hostname;
use Carp;
require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(hostname);
=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 C<syscall(SYS_gethostname)>,
C<`hostname`>, C<`uname -n`>, and the file F</com/host>.
If all that fails it C<croak>s.
All nulls, returns, and newlines are removed from the result.
=head1 AUTHOR
David Sundstrom E<lt>F<sunds@asictest.sc.ti.com>E<gt>
Texas Instruments
=cut
sub hostname {
# method 1 - we already know it
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!
$host = '';
Carp::croak "Cannot get host name of local machine";
}
elsif ($^O eq 'MSWin32') {
($host) = gethostbyname('localhost');
chomp($host = `hostname 2> NUL`) unless defined $host;
return $host;
}
else { # Unix
# method 2 - syscall is preferred since it avoids tainting problems
eval {
local $SIG{__DIE__};
{
package main;
require "syscall.ph";
}
$host = "\0" x 65; ## preload scalar
syscall(&main::SYS_gethostname, $host, 65) == 0;
}
# method 3 - trusty old hostname command
|| eval {
local $SIG{__DIE__};
$host = `(hostname) 2>/dev/null`; # bsdish
}
# method 4 - sysV uname command (may truncate)
|| eval {
local $SIG{__DIE__};
$host = `uname -n 2>/dev/null`; ## sysVish
}
# method 5 - Apollo pre-SR10
|| eval {
local $SIG{__DIE__};
($host,$a,$b,$c,$d)=split(/[:\. ]/,`/com/host`,6);
}
# bummer
|| Carp::croak "Cannot get host name of local machine";
# remove garbage
$host =~ tr/\0\r\n//d;
$host;
}
}
1;
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