Path: utzoo!attcan!uunet!vsedev!logan
From: logan@vsedev.VSE.COM (James Logan III)
Newsgroups: comp.unix.questions
Subject: Re: Subprocess lives on..........
Keywords: Bourne shell loop
Message-ID: <1237@vsedev.VSE.COM>
Date: 15 Nov 88 16:33:43 GMT
References: <167@heart-of-gold>
Reply-To: logan@vsedev.VSE.COM (James Logan III)
Organization: VSE Software Development Lab
Lines: 40

In article <167@heart-of-gold> jc@heart-of-gold (John M Chambers) writes:
>Can anyone figure out how to make the while-loop exit when graf terminates
>and the script exits?  I've tried playing arount with $? and traps, but I 
>clearly don't know what I'm doing.  I even tried a "kill -HUP 0", and it
>worked.  But all my windows also exited and I got a login prompt.  Sorta
>overkill, if you ask me.

The shell really should exit without leaving the while loop
running (at least under Sys V) because the while loop will be
writing on a pipe with no one to read it.  This SHOULD cause a
SIGPIPE signal to kill the subshell that's running the while
loop.  Even if the subshell was ignoring the SIGPIPE signal, I
can't see how it would start writing to your terminal!  My first
guess at a fix is this:  

#!/bin/sh
#   GrafRoute host
# This generates a graph of the "netstat -r" Use data for host, 
# which may be the destination or the gateway.
# 
(
	trap "exit 0" 1 13 15;
	while true; do
		netstat -r |
		grep $1 |
		cut -c49-59;
		sleep 6;
	done;
) |
graf -PD +H +V -a -T'Route "'$1'" packet rate';

I don't know what SunView does to terminate the process.  Maybe
it sends a SIGHUP or a SIGTERM?  Anyway, this script will exit
when it receives either signal. (Theoretically!) 

			-Jim
-- 
Jim Logan		logan@vsedev.vse.com
(703) 892-0002		uucp:	..!uunet!vsedev!logan
			inet:	logan%vsedev.vse.com@uunet.uu.net