Path: utzoo!attcan!uunet!cs.utexas.edu!mailrus!uflorida!usfvax2!tct!chip
From: chip@tct.uucp (Chip Salzenberg)
Newsgroups: comp.lang.perl
Subject: Re: gethostname() in perl
Message-ID: <25D02290.62B4@tct.uucp>
Date: 7 Feb 90 13:28:48 GMT
References: <1018@frankland-river.aaii.oz.au>
Organization: ComDev/TCT, Sarasota, FL
Lines: 43

According to pem@frankland-river.aaii.oz.au (Paul E. Maisano):
>This is how I find the hostname of the machine I am running on.
>
>    do 'syscall.pl' || die "syscall.pl: $@\n";
>
>    $host = "\0" x 100;		# pre-nulled buffer for hostname
>    syscall($SYS_GETHOSTNAME, $host, length($host));
>
>syscall.pl is just of file of system call numbers.

A comparable method could be used under SysV, with $SYS_UNAME.
Unfortunately, a portable definition of "struct utsname" is not
possible -- every vendor does it differently.  Sigh.

It's worth noting that Xenix systems have uname(), but the "real"
(UUCP) hostname is actually in a file: /etc/systemid.  So the Perl
version of gethostname() for Xenix looks like:

	sub gethostname() {
		local(*id);
		return "unknown" unless open(id, "/etc/systemid");
		$id = <id>;
		close(id);
		chop($id);
		$id;
	}

I can't think of a portable definition of gethostname() that would be
meaningful.  Something close [:-)] would be:

	if Xenix, then
		read /etc/systemid;
	else if gethostname() is available, then
		gethostname();
	else if uname() is available, then
		use nodename from utsname structure;
	else
		"";

Would anything be broken with this algorithm?
-- 
Chip Salzenberg at ComDev/TCT   <chip%tct@ateng.com>, <uunet!ateng!tct!chip>
          "The Usenet, in a very real sense, does not exist."