Path: utzoo!mnetor!uunet!mcvax!unido!pcsbst!jh
From: jh@pcsbst
Newsgroups: comp.unix.questions
Subject: Re: wait3 emulation in SYSTEMV ?? - (nf)
Message-ID: <4200004@pcsbst.UUCP>
Date: 18 Jan 88 09:20:00 GMT
References: <360@rruxa.UUCP>
Lines: 37
Nf-ID: #R:rruxa:-36000:pcsbst:4200004:000:863
Nf-From: pcsbst!jh    Jan 18 10:20:00 1988

The newer versions of System V provide the possibilty to check
the existence of a process by sending a signal 0 to the process
in question and checking for an error return. This would allow
you to write a write a pseudo wait3() function for terminated
processes:

int wait3_for_sysV (testpid, status, options, rusage)
int testpid;
union wait * status;
int options;
struct rusage * rusage;         /* not used */
{
	....
	if (options & WNOHANG) {
		if (kill (testpid, 0) == -1) {
			if (errno != EPERM)
				return (wait (status));
			else
				return (BUG);
		} else {
			return (STILLRUNNING);
		}

	} else {
		return (wait (status));
	}
}


This is only an example. Check for possible different error
returns of the kill() system call. For a better implementation
you should poll all pids in question.

I hope this did help you.

	Johannes Heuft
	unido!pcsbst!jh