Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!ukma!tut.cis.ohio-state.edu!osu-cis!att!chinet!les
From: les@chinet.chi.il.us (Leslie Mikesell)
Newsgroups: comp.unix.questions
Subject: Re: Getting rid of a <defunct> process
Message-ID: <7702@chinet.chi.il.us>
Date: 13 Feb 89 05:10:36 GMT
References: <102@avatar.UUCP> <27866@bu-cs.BU.EDU>
Reply-To: les@chinet.chi.il.us (Leslie Mikesell)
Distribution: usa
Organization: Chinet - Public Access Unix
Lines: 27

In article <27866@bu-cs.BU.EDU> madd@bu-it.bu.edu (Jim Frost) writes:
>In article <102@avatar.UUCP> kory@avatar.UUCP (Kory Hamzeh) writes:
>|The main process (the parent which does all of the forks) can not
>|do a wait() because I can't get blocked for anything. 

 >What I usually do is:

 >	fireman() /* catches falling children */
 >	{ union wait wstatus;
 >	  while (wait3(&wstatus, WNOHANG, NULL) >= 0)
 >	    ;
 >	}
 
 >	main()
 >	{
 >	  signal(SIGCHLD, fireman);
 >          /*...*/
 >        }

SysV only has wait(), and signals are not queued or deferred inside the
handlers.  However, SIGCHLD is a little different (otherwise init would
not work).  If a defunct process exists when the signal(SIGCHLD,...)
call is made, the signal happens immediately.  Putting a
signal(SIGCHLD,fireman) as the last statement in the fireman() function
will give the effect of queued signals.

Les Mikesell