Subject: Re: serial line ideas
To: Curt Sampson <>
From: Phil Knaack <>
List: current-users
Date: 11/15/1996 14:05:53
>On Wed, 13 Nov 1996, Greg A. Woods wrote:

>> [ On Sat, November 9, 1996 at 18:25:49 (-0800), Don Lewis wrote: ]

>> Hopefully the process doing the killing is running as "uucp" or
>> something similar and can't kill your average innocent process.

>I'm not sure where the killing comes in here; in my proposal (and
>in all implemenations of LCK..ttyXX files I'm aware of) nothing
>gets killed. There's just a check to see if a process with that
>PID is currently running, and if there is, the lock is assumed to
>be valid.

	Just a minor clarification here .. not that this contributes 
in any way to the real target of the discussion .. :)

	One of the common ways to determine if a PID exists is to send
it a signal 0 .. signal 0 just bounces off the process without any effect;
if the process doesn't exist, you get ESRCH.

	However, even sending a signal 0 is subject to the process's 
credentials, and a UUCP-owned process sending signal 0 to a non-UUCP 
process will return EPERM.

Phillip F Knaack
Database Programmer, Information Development for Extension Audiences (IDEA)
Iowa State University Extension