Subject: Re: serial line ideas
To: Phil Knaack <>
From: Curt Sampson <>
List: current-users
Date: 11/15/1996 12:07:06
On Fri, 15 Nov 1996, Phil Knaack wrote:

> 	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.

Which is fine, BTW. If you get ESRCH, you know the process doesn't
exist; if you get EPERM or no error, you know it does exist. This
is how I coded it, and uucp has to trouble determining whether the
lock is `alive' or not.


Curt Sampson		Info at
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