Given PID, make sure a process is running on Unix?

[Jarkko Torppa]

In article <3D2770A8.7070900 at ob_scure.dk>, Thomas Jensen wrote:
> VanL wrote:
>> Hello,
>> 
>> I am trying to get write a python script that  on Unix reads a PID from 
>> a file and, if that process is still running, exits.  If the process is 
>> not running, the process would be started.
>> 
>> I have everything written except the part that makes sure the process is 
>> running.  I have poked through the os module, but I can only seem to 
>> find information about the current process or child processes, not just 
>> some arbitrary process.
> 
> If your system has a 'proc' device, you could do something like this:
>      os.path.isdir('/proc/%d' % pid)
> Most Unix flavours have a proc device AFAIK.

All(?) unix flawors have kill(2)
>>> import os
>>> os.kill(12331,0)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
OSError: [Errno 3] No such process
>>> os.kill(os.getpid(),0)
>>> 

-- 
Jarkko Torppa, Elisa Internet