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Wiebe Vos
Guest
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 Posted: Sun Apr 09, 2006 9:03 pm Post subject: OpenProcess() returns different handles |
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BCB6 + WinXP(Pro)
//
PROCESS_INFORMATION processInfo;
//
I sucessfully launch an app with CreateProcess(...)
However thereafter OpenProcess ( PROCESS_ALL_ACCESS, true,
processInfo.dwProcessId)
returns a handle that differs from processInfo.hProcess
(In fact it returns a different handle each time when called.)
Why?
Thanks in advance,
Wiebe |
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Eric Noel
Guest
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| Posted: Sun Apr 09, 2006 10:03 pm Post subject: Re: OpenProcess() returns different handles |
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Wiebe Vos wrote:
| Quote: | I sucessfully launch an app with CreateProcess(...)
However thereafter OpenProcess ( PROCESS_ALL_ACCESS, true,
processInfo.dwProcessId)
returns a handle that differs from processInfo.hProcess
(In fact it returns a different handle each time when called.)
Why?
|
WAD. Think of it as if you were opening a file handle - you can open the
same file multiple times, each handle can have different access, and be
used independently. Same idea in this case for your process handle.
- Eric |
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Wiebe Vos
Guest
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| Posted: Mon Apr 10, 2006 9:03 am Post subject: Re: OpenProcess() returns different handles |
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Thanks,
I want to use the returned handle to check if the program is (still) alive
and be able to kill it.
However GetExitCodeProcess ( returnedHandle, &exitCode) gives exitCode=0.
How can I get the appropriate handle to do so, when I have the processId?
Wiebe |
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Wiebe Vos
Guest
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| Posted: Mon Apr 10, 2006 9:03 am Post subject: Re: OpenProcess() returns different handles |
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BTW. It is a console program. (no window)
Wiebe |
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Wiebe Vos
Guest
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| Posted: Mon Apr 10, 2006 10:03 am Post subject: Re: OpenProcess() returns different handles |
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Never mind.
The dwDesiredAccess parameter in OpenProcess() deals with that.
FWIW:
PROCESS_QUERY_INFORMATION gives the handle to determine the program status.
PROCESS_TERMINATE gives the license to kill.
Wiebe |
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Bob Gonder
Guest
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| Posted: Mon Apr 10, 2006 5:03 pm Post subject: Re: OpenProcess() returns different handles |
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Wiebe Vos wrote:
| Quote: | I want to use the returned handle to check if the program is (still) alive
and be able to kill it.
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The hProcess member of the PROCESS_INFORMATION structure you passed to
CreateProcess() should give you that handle.
{Note: I am not recommending this code. It is for illustration
purposes only}
if( CreateProcess( 0, command, 0, 0, FALSE, NORMAL_PRIORITY_CLASS,
0, 0, &si, &pi ) )
{
CloseHandle( pi.hThread );
do{
WaitForSingleObject( pi.hProcess, 100);
GetExitCodeProcess ( pi.hProcess, &exitCode);
}while( exitCode == STILL_ACTIVE );
CloseHandle( pi.hProcess );
};
| Quote: | However GetExitCodeProcess ( returnedHandle, &exitCode) gives exitCode=0.
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Did you check the return value of the function itself?
if( ! GetExitCodeProcess ( pi.hProcess, &exitCode) )
ReportError( "GetExitCodeProcess", GetLastError() );
One also wonders why you ask for the handle to be inheritable (true)?
> OpenProcess ( PROCESS_ALL_ACCESS, true, processInfo.dwProcessId) |
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Wiebe Vos
Guest
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| Posted: Mon Apr 10, 2006 7:03 pm Post subject: Re: OpenProcess() returns different handles |
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Hi Bob,
| Quote: | The hProcess member of the PROCESS_INFORMATION structure you passed to
CreateProcess() should give you that handle. |
Correct. However thereafter the launched app is bound to be terminated
and/or
"replaced".
| Quote: | ...why you ask for the handle to be inheritable (true)?
No specific reason. Taken from an example. |
As indicated in my earlier response, I managed to find a solution.
Thanks for your help,
Wiebe |
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