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From: rml@hpfcdc.HP.COM (Bob Lenk)
Newsgroups: comp.sys.hp
Subject: Re: UNIX WAIT3 function
Message-ID: <5570011@hpfcdc.HP.COM>
Date: Thu, 20-Aug-87 11:59:47 EDT
Article-I.D.: hpfcdc.5570011
Posted: Thu Aug 20 11:59:47 1987
Date-Received: Sun, 23-Aug-87 14:38:14 EDT
References: <1467@mit-amt.MEDIA.MIT.EDU>
Organization: HP Ft. Collins, Co.
Lines: 23

While wait3(2) is indeed documented on the wait(2) manual page, it is
currently supported only on the series 800.  Since the question was on
the series 300 ("Bobcat") the answer is that wait3 is not available.
Wait3 is a BSD-derived call; there are two ways in the System V world to
get similar functionality (to a nonblocking wait):

	1) Set a timeout with alarm(2) (or for a shorter timeout
	   setitimer(2) - a BSD feature that is supported on the 300).

	2) Only call wait(2) in response to a SIGCLD signal.  Because of
	   the semantics of SIGCLD (different from BSD SIGCHLD), you can
	   be guaranteed exactly one signal per terminated child, and
	   thus a wait(2) that will not block.  Note that the SIGCLD
	   signal handler must be coded to call wait(2) and to
	   re-install the signal handler with signal(2) or sigvector(2)
	   after the call to wait(2).

The latter is probably a better way to structure code intended for
System V, but may require more modification to code originally written
for BSD.  A timeout can be used to directly emulate non-blocking wait3.

		Bob Lenk
		{ihnp4, hplabs}!hpfcla!rml