topic Re: Terminate -0 terminates process in Operating System - HP-UX

Kill -0 kills process

Vincent Farrugia — Tue, 21 May 2002 07:50:12 GMT

Hello,

How can the above happen? We have a process whereby we wish to check whether it is alive using kill -0 (SIGNULL). Instead, it is killed like a kill -9. How can this be? All other processes are not killed by kill -0, as usual.

Thanks,
Vince

Re: Kill -0 kills process

Steven Sim Kok Leong — Tue, 21 May 2002 07:57:43 GMT

Hi,

This is indeed unusual. You may like to update your system patches in the hope that this is a system bug.

Hope this helps. Regards.

Steven Sim Kok Leong

Re: Kill -0 kills process

Ruediger Noack — Tue, 21 May 2002 08:01:13 GMT

It depends of the programmers code how to handle a signal. Seems in your case the SIGNULL performs an exit.

Ruediger

Re: Kill -0 kills process

Rainer von Bongartz — Tue, 21 May 2002 08:07:41 GMT

The application has it's own signal handler installed.

In an application you can define what to do upon receiving a signal. (using call sigset).

The application has the exit() function installed in its signal handler as a reaction to receiving signal 0.

Regards
Rainer

Re: Kill -0 kills process

Duncan Edmonstone — Thu, 30 Jun 2022 10:36:09 GMT

I don't think it can be the signal handler in the process, as according to the man page for terminate, it never gets a signal:

SIGNULL (0), the null signal, invokes error checking but no signal is
actually sent. This can be used to test the validity or existence of
pid.

Very strange... what is the process in question?

Duncan

Re: Kill -0 kills process

Carlos Fernandez Riera — Tue, 21 May 2002 08:34:45 GMT

If the process is a shell sig 0 is ERR (syntax error) , and then execute exit from the function ( if any) or script.

See man sh (trap).

HTH

Re: Kill -0 kills process

Vincent Farrugia — Tue, 21 May 2002 09:07:14 GMT

The process is one used by a database software. The machine is new (rp5450) and contains the latest March 2002 patches.

Re: Kill -0 kills process

Deepak Extross — Tue, 21 May 2002 09:33:05 GMT

Hi,

Can you just confirm that a "kill -0" is being used, and not a "kill 0".

Re: Kill -0 kills process

harry d brown jr — Tue, 21 May 2002 10:54:57 GMT

Vince,

You don't have "kill" aliased do you?

Have you tried this manually from the command line on the process, because I'm assuming you have a script that is checking to see if the process is running?

Also, what shell are you using for your script?

live free or die
harry

Re: Kill -0 kills process

Vincent Farrugia — Tue, 21 May 2002 12:15:44 GMT

Hello,

I'm using kill -s 0. Only this process is being killed, the others aren't, so no alias. I tried it on a script and also on the command line. I'm using the normal sh shell.

Vince

Re: Terminate -0 terminates process

Duncan Edmonstone — Thu, 30 Jun 2022 08:13:19 GMT

Isn't terminate a built-in in the standard HP-UX POSIX shell? WHat happens if you explicitly specify /usr/bin/terminate instead?

HTH

Duncan

Re: Kill -0 kills process

Ruediger Noack — Tue, 21 May 2002 12:35:58 GMT

May be tusc (an aquivalent to truss) will help you to find out what happens.
Look in this thread where tusc is to download:
http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x3d9fee3e323bd5118fef0090279cd0f9,00.html

Good luck
Ruediger

Re: Kill -0 kills process

Wodisch — Tue, 21 May 2002 13:59:15 GMT

Hi,

actually it might be more about your shell, than about the signal handler: in the past it was a kind of custom to send kill to pseudo-pid 0 in order to kill all processes of your *session* (ascii-terminal session, remind you).
So the kill command was implemented differently (might have been a "built-in" command, i.e. built-into the shell, like "cd").

FWIW,
Wodisch