Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!mcsun!ukc!stl!robobar!ronald
From: ronald@robobar.co.uk (Ronald S H Khoo)
Newsgroups: comp.lang.perl
Subject: Re: While learning PERL... a suggestion
Message-ID: <1991Jan22.080310.5582@robobar.co.uk>
Date: 22 Jan 91 08:03:10 GMT
References: <118879@uunet.UU.NET> <1991Jan21.092204.11944@ux1.cso.uiuc.edu> <119430@uunet.UU.NET>
Organization: Robobar Ltd., Perivale, Middx., ENGLAND.
Lines: 36

rbj@uunet.UU.NET (Root Boy Jim) writes:

> Another thing perl needs is the ability to create lock files. Sysopen?

Eh ?  You're not advocating the use of O_CREAT|O_EXCL for lockfiles are
you ?  That's not portable.  It doesn't work on my machine for one :-)
Why not do lockfiles like C News does them ?

[ Question: did I get the $SIG{} = stuff right ? it's a little hard to test ..]

# =()<$NEWSCTL = "@<NEWSCTL>@";>()=
$NEWSCTL = "/usr/lib/news";

$ltmp	= "$NEWSCTL/LTMP.$$";
$lock	= "$NEWSCTL/LOCK";

sub Handler	{  unlink($lock, $ltmp) if $locked; exit 1;   }
sub Lock {
	open (LTMP, ">$ltmp") || die "cannot write to $ltmp: $!\n";
	print LTMP "$$\n"; close(LTMP);
	until ($locked) {
		if (link($ltmp, $lock)) {
			$locked = 1;
		} else {
			sleep 30;
		}
	}
	$SIG{'HUP'} = $SIG{'INT'} = $SIG{'TERM'} = 'Handler';
}

sub UnLock {
	unlink ($lock, $ltmp) if $locked;
	$locked = 0;
}
-- 
Ronald Khoo <ronald@robobar.co.uk> +44 81 991 1142 (O) +44 71 229 7741 (H)