Newbie - Process Management

[Chris Gonnerman]

----- Original Message -----
From: "Dan Scholey" <scholeyd at logica.com>


> Hi,
>
> I am hoping you can help me, I am fairly new to python (and Unix) but am
> trying to solve the following problem...
>
> I want to be able to check if a parent process has died.
>
> At the moment I can check that a child process has died using...
>
>         status = (os.waitpid(child, os.WNOHANG))[0]
>         if status!=0:
>
> I've looked at several manuals and can't find a similar function for
parent
> processes.
> Obviously I know both the parent and child process id ( get_pid() /
> get_ppid() ).

Here is a partial screen-capture from my Linux system.  If you are using any
standard Unixoid OS this should work:

<< partial ps listing >>

15321 pts/1    S      0:00 -bash
15377 ?        S      0:00 /usr/sbin/httpd -f /etc/httpd/httpd.conf
15521 pts/1    R      0:00 ps ax

office:~ $ python
Python 2.1.2 (#1, Jan 16 2002, 17:04:23)
[GCC egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)] on linux2
Type "copyright", "credits" or "license" for more information.
>>> import os
>>> os.kill(15321,0)
>>> os.kill(15322,0)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
OSError: [Errno 3] No such process
>>>

In other words, PID 15321 exists (I knew it did, it's my shell) but 15322
doesn't.  So:

    def parentcheck():
        try:
            os.kill(os.get_ppid(), 0)
            return 1
        except OSError:
            return 0


> I have a workaround of....
>
>         ps_line=string.split(commands.getoutput("ps -lp
%s"%my_pid),"\012")
>         if string.atoi(string.split(ps_line[1])[4])!=daddy:
>
> ... but I would rather not use ps.
>
> Any ideas?

Hope this helps.

> Cheers
> Dan

Chris Gonnerman -- chris.gonnerman at newcenturycomputers.net
http://newcenturycomputers.net