Running status of a process

Running status of a process

[Prasanta Sadhukhan]

Hi,

Can anyone point as to how can I obtain the information whether a 
non-child process is still running?

I tried waitpid(pid, &status, WNOHANG) but always receive return value 
as -1 with errno as ECHILD.
Since the processes I am waiting for is not the child of this process 
from where I am calling waitpid() (ie, they are independant processes), 
it might be a valid error but what is the other alternative?

Regards
Prasanta

Re: Running status of a process

[Steve Graegert]

Prasanta,

On 3/21/07, Prasanta Sadhukhan <Prasanta.Sadhukhan@sun.com> wrote:
> Hi,
>
> Can anyone point as to how can I obtain the information whether a
> non-child process is still running?

If you know the PID of the process you want to obtain the status of
use the kill(2) system call.  The second argument should be 0 (zero)
to prevent a signal from being sent to the process.  If the process
exists kill(2) returns zero, or -1 otherwise.

kill(2) can indicate various errors, but an error or EPERM usually is
an indicator that the process exists, while all others indicate that
it does not.

If you're writing for systems supporting the /proc filesystem,
checking for existence of /proc/{pid} is an alternative.

If you don't know the PID you're out of luck, unless you make use of
the /proc filesystem again, which is not portable per se.

	\Steve

--

Steve Grägert <steve@graegert.com>
Jabber    xmpp://graegerts@jabber.org
Internet  http://eth0.graegert.com, http://blog.graegert.com
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Re: Running status of a process

[Prasanta Sadhukhan]

Steve Graegert wrote:

> Prasanta,
>
> On 3/21/07, Prasanta Sadhukhan <Prasanta.Sadhukhan@sun.com> wrote:
>
>> Hi,
>>
>> Can anyone point as to how can I obtain the information whether a
>> non-child process is still running?
>
>
> If you know the PID of the process you want to obtain the status of
> use the kill(2) system call.  The second argument should be 0 (zero)
> to prevent a signal from being sent to the process.  If the process
> exists kill(2) returns zero, or -1 otherwise.
>
> kill(2) can indicate various errors, but an error or EPERM usually is
> an indicator that the process exists, while all others indicate that
> it does not.
>
> If you're writing for systems supporting the /proc filesystem,
> checking for existence of /proc/{pid} is an alternative.
>
> If you don't know the PID you're out of luck, unless you make use of
> the /proc filesystem again, which is not portable per se.

thanks steve, found the solution.. I guess my mail crossed yours in the path

Prasanta

>
>     \Steve
>
> -- 
>
> Steve Grägert <steve@graegert.com>
> Jabber    xmpp://graegerts@jabber.org
> Internet  http://eth0.graegert.com, http://blog.graegert.co
> m



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Re: Running status of a process

[Prasanta Sadhukhan]

Prasanta Sadhukhan wrote:

> Hi,
>
> Can anyone point as to how can I obtain the information whether a 
> non-child process is still running?
>
> I tried waitpid(pid, &status, WNOHANG) but always receive return value 
> as -1 with errno as ECHILD.
> Since the processes I am waiting for is not the child of this process 
> from where I am calling waitpid() (ie, they are independant 
> processes), it might be a valid error but what is the other alternative?
>
> Regards
> Prasanta

Got it...Should have called kill(pid, 0)
Thanks anyways

>
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