How to know if a process is zombie?

Ruby
1

Hi, after some forks I need to know if a process still is alive or not,
but in
case it’s alive I also need to know if it’s a zombie process (it died
without
Process.wait or Process.detach).

Unfortunatelly I couln’t find how to know it using Process module:
module Process - RDoc Documentation
class Process::Status - RDoc Documentation

Is there any other way to determine if a given PID is zombie?
Thanks.

2

On 26.12.2009 17:53, Iñaki Baz C. wrote:

Hi, after some forks I need to know if a process still is alive or not, but in
case it’s alive I also need to know if it’s a zombie process (it died without
Process.wait or Process.detach).

Unfortunatelly I couln’t find how to know it using Process module:
module Process - RDoc Documentation
class Process::Status - RDoc Documentation

Is there any other way to determine if a given PID is zombie?

I believe you can use Process.kill(0, suspicious_pid) and if you get
“Errno::ESRCH: No such process” it does not exist any more or is a
zombie. Then you can use Process.waitpid(suspicious_pid,
Process::WNOHANG) to end his martyrdom and get the exit code.

It’s probably better to set up a signal handler though. But that
totally depends on your use case.

Kind regards

robert

3

El Sábado, 26 de Diciembre de 2009, Robert K.
escribió:>

I believe you can use Process.kill(0, suspicious_pid) and if you get
“Errno::ESRCH: No such process” it does not exist any more or is a
zombie.

Unfortunatelly I’ve already checked it and doesn’t work since a zombie
process
does exist and does receive signals, so Process.kill(0, suspicious_pid)
returns true.

Anyhow I found a better approach so now I don’t need need to know if a
process
is zombie.

Thanks a lot.

4

On 26.12.2009 19:13, Iñaki Baz C. wrote:

I believe you can use Process.kill(0, suspicious_pid) and if you get
Thanks a lot.
Thank you for the heads up!

Kind regards

robert

5

Hi,

Am Sonntag, 27. Dez 2009, 01:53:42 +0900 schrieb Iñaki Baz C.:

Hi, after some forks I need to know if a process still is alive
or not, but in case it’s alive I also need to know if it’s a
zombie process (it died without Process.wait or Process.detach).

Unfortunatelly I couln’t find how to know it using Process module:

Is there any other way to determine if a given PID is zombie?

trap “SIGCHLD” do |sig| puts “A child became a zombie.” end

This tells you when it happened. As far as I know there is no way
to find out which process it was. I recommend waiting
(Process.waitpid) for every pid you forked.

Bertram

6

El Sábado, 26 de Diciembre de 2009, Bertram S.
escribió:>

trap “SIGCHLD” do |sig| puts “A child became a zombie.” end

This tells you when it happened. As far as I know there is no way
to find out which process it was. I recommend waiting
(Process.waitpid) for every pid you forked.

Thanks a lot.