Getting rid of a <defunct> process

[Leslie Mikesell]

In article <27866 at bu-cs.BU.EDU> madd at bu-it.bu.edu (Jim Frost) writes:
>In article <102 at avatar.UUCP> kory at 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