How to know if a process is zombie?

ruby-talk
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:
  http://ruby-doc.org/core/classes/Process.html
  http://ruby-doc.org/core/classes/Process/Status.html

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

···

--
Iñaki Baz Castillo <ibc@aliax.net>

2

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

···

On 26.12.2009 17:53, Iñaki Baz Castillo 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?

--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

3

Hi,

···

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

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

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
*
Discover String#notempty? at <http://raa.ruby-lang.org/project/step&gt;\.

4

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.

···

El Sábado, 26 de Diciembre de 2009, Robert Klemme escribió:

On 26.12.2009 17:53, Iñaki Baz Castillo 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.

--
Iñaki Baz Castillo <ibc@aliax.net>

5

Thanks a lot.

···

El Sábado, 26 de Diciembre de 2009, Bertram Scharpf escribió:

Hi,

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

--
Iñaki Baz Castillo <ibc@aliax.net>

6

Thank you for the heads up!

Kind regards

  robert

···

On 26.12.2009 19:13, Iñaki Baz Castillo wrote:

El Sábado, 26 de Diciembre de 2009, Robert Klemme escribió:

On 26.12.2009 17:53, Iñaki Baz Castillo 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.

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.

--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/