easy question about kill command

[Roman Gorohov.]

Hi, Oliver.

> roma.a.g <roma.a.g at gmail.com> wrote:
 >> Is there anyone who can explain me, why when i say 'kill -HUP id',
 >> and its failed to restart, kill say nothing?

> Because the kill command has no way to know about it.

> The kill command only instructs the kernel to deliver
> a signal to a process (or to a process group).  The only
> feedback it gets from the kernel is whether the target
> process exists or not.  (The latter is often used to
> check for the existence of a particular process ID, by
> trying to send it a "zero" signal which does nothing.)

> There is no way for the kill command to know what the
> target process is going to do with the signal.  This is
> entirely and only the business of the target process,
> which might chose to take the default action (in the case
> of SIGHUP it's to terminate the process), to ignore the
> signal alltogether, or to take some special action.
> Some programs use SIGHUP traditionally to rotate their
> logfiles, re-read configuration files, re-open network
> sockets, restart themselves, or other things.  But that's
> entirely up to the program in question, and there is no
> way the kill command could know about it, let alone
> whether it was successful or not.

Thanks for your reply. My question was about standard bsd daemons, not
about some apps with unpredictable behaviour.

 >> It is such an easy to implement...

> I don't think so, as explained above.

Yeah right, I see now.


> Best regards
>    Oliver




-- 
Best regards,
Roman Gorohov                         mailto:roma.a.g at gmail.com