Path: utzoo!utgpu!watserv1!watmath!att!cbnews!jrl
From: jrl@cbnews.att.com (john.lupien)
Newsgroups: comp.unix.wizards
Subject: Re: How can a parent find out if one of its children is still alive
Message-ID: <1990Jun5.201351.27357@cbnews.att.com>
Date: 5 Jun 90 20:13:51 GMT
References: <30408@cup.portal.com> <6334@ozdaltx.UUCP>
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 29

In article <6334@ozdaltx.UUCP> toma@ozdaltx.UUCP (Tom Armistead) writes:
>In article <30408@cup.portal.com>, DeadHead@cup.portal.com (Bruce M Ong) writes:
>> I am sure there is a very easy way to do this, but I just havent
>> figured this one out:
>> 	How can a parent find out if one of its children is still alive
>> or not without
>If you have the process id of the child you can use kill(2) to find out if
>it is still there.
>i.e.:   if( kill( child_pid, 0 ) == -1 )
>            puts( "The child is dead" );
>Signal 0 is called the NULL signal and is used to validate a process id, no 
>signal is actually sent to the destination process.

This is nice in that, with a small 
change, you can use it to find
out if processes belonging to
other uid's are alive, provided
you know their pid. If kill(child_pid, 0)
returns other than -1, the process exists
and you have permission to kill (007?)
If it returns -1 and an errno of ESRCH,
the pid does not exist, otherwise you
typically get errno of EPERM.


-- 
	-John Lupien
	mvuxr!jrl
	jrl@mvuxr.att.com