?RCS: $Id: d_pidcheck.U 167 2013-05-08 17:58:00Z rmanfredi $
?RCS:
?RCS: Copyright (c) 1991-1997, 2004-2006, Raphael Manfredi
?RCS: 
?RCS: You may redistribute only under the terms of the Artistic License,
?RCS: as specified in the README file that comes with the distribution.
?RCS: You may reuse parts of this distribution only within the terms of
?RCS: that same Artistic License; a copy of which may be found at the root
?RCS: of the source tree for dist 4.0.
?RCS:
?RCS: $Log: d_pidcheck.U,v $
?RCS: Revision 3.0.1.1  1997/02/28  15:37:55  ram
?RCS: patch61: replaced .o with $_o all over the place
?RCS: patch61: added ?F: metalint hint
?RCS:
?RCS: Revision 3.0  1993/08/18  12:06:46  ram
?RCS: Baseline for dist 3.0 netwide release.
?RCS:
?MAKE:d_pidcheck: cat rm +cc _o
?MAKE:	-pick add $@ %<
?S:d_pidcheck:
?S:	This variable conditionally defines the variable PIDCHECK
?S:	which indicates that kill(pid, 0) will check for an active pid.
?S:.
?C:PIDCHECK:
?C:	This symbol, if defined, means that the kill(pid, 0) will
?C:	check for an active pid (i.e. the kernel will run all the
?C:	necessary pid checks, but no signal is actually sent).
?C:.
?H:#$d_pidcheck PIDCHECK		/**/
?H:.
?F:!try
: check for "kill(pid, 0)"
echo " "
case "$d_pidcheck" in
"$define")
echo "I already know your system supports kill(pid, 0) for pid checks." >&4
	;;
"$undef")
echo "We both know your system does not support signal #0 for pid checks." >&4
	;;
*)
	echo "Checking to see if kill(pid, 0) works..." >&4
	$cat >try.c <<'EOCP'
int main()
	{
	int	pid, status0, status9;

	if ((pid = fork()) == 0)
		{
		sleep(30);
		exit(1);
		}
	status0 = kill(pid, 0);
	status9 = kill(pid, 9);
	exit(status0 == status9);
	}
EOCP
	if $cc -o try try.c >/dev/null 2>&1 ; then
		if ./try >/dev/null 2>&1 ; then
			echo "Yes, it does marvels."
			d_pidcheck="$undef"
		else
			d_pidcheck="$define"
			echo "No, it doesn't."
		fi
	else
		echo "(I was unable to compile the test program.)"
		echo "Your system does not appear to support kill(pid, 0)."
		d_pidcheck="$undef"
	fi
	$rm -f try.c try$_o try
	;;
esac