Re: kill doesn't work correctly

Hi Jan,

I have tried for too many times with wrong results, so I doubt that exactly 
that process ID gets used each time.

But I have tried the following program which always work:

use Win32::Process::Info;

my $pid = 3272;

my @pids = Win32::Process::Info->new->ListPids;

print grep($_ == $pid, @pids) ? 'yes' : 'no';

Thanks.

--
Octavian

----- Original Message ----- 
From: "Jan Dubois" <[email protected]>
To: "'Octavian Rasnita'" <[email protected]>; 
<[email protected]>
Sent: Tuesday, April 06, 2010 1:21 AM
Subject: RE: kill doesn't work correctly


> On Mon, 05 Apr 2010, Octavian Rasnita wrote:
>>
>> C:\Documents and Settings\Octavian>taskkill /pid 1980
>> ERROR: The process "1980" not found.
>> C:\Documents and Settings\Octavian>perl -v
>> This is perl, v5.10.1 built for MSWin32-x86-multi-thread
>> (with 2 registered patches, see perl -V for more detail)
>> C:\Documents and Settings\Octavian>perl -e "print kill(0, 1980);"
>> 1
>>
>> So the process with the PID 1980 doesn't exist, but kill(0) reports that 
>> it exists.
>> Am I doing something wrong or there is a bug in this version of Perl?
>
> I can't reproduce the problem with either build 1006 nor 1007
> (the only 5.10.1 builds of ActivePerl released so far), so I have
> no idea why this is failing for you.
>
> I checked both Windows XP and Windows 7, FWIW.
>
> The only 2 explanations I can come up with are:
>
> 1) The perl process above gets the pid 1980.  Windows reuses pids quite 
> rapidly,
>   so you should print out $$ in your sample script to make sure you are 
> not
>   using this supposedly non-existing pid.
>
> 2) Something else spawns a new process between the time you run 
> taskkill.exe
>   and perl.exe, and that new process gets pid 1980.
>
> kill(0, $pid) on Perl essentially just calls
>
>    handle = OpenProcess(PROCESS_TERMINATE, FALSE, pid);
>
> and if the handle is not NULL then it returns '1', otherwise it returns
> '0'.  I don't see how OpenProcess() could return a valid process handle
> if the PID is not valid at the time of the call.  The OpenProcess
> documentation is here:
>
>    http://msdn.microsoft.com/en-us/library/ms684320%28VS.85%29.aspx
>
> Cheers,
> -Jan
>
>
>
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