Tprocess - how to force close of child process

[jaz2014]

I have a Tprocess running fine and everything works.
The process runs a cmd.exe shell which in turn runs ffmpeg

Iwant to be able to force closure of the child shell (killing ffmpeg obviously) but cant seem
to see how to do that.
Ideally I want to do it whether I have a console window open or not.

I've tried windows messaging and everything else I can find here but nothing seems
to reference killing a child program.

Can anyone tell me the simplest way to do his ?

thanks

[Roland57]

Hello. Here is a procedure that I use:

Code: Pascal  [Select][+][-]

1. procedure TForm1.AbortProcess(const AExeName: string);
2. var
3.   LStr: string;
4. begin
5.   DebugLn(Format('AbortProcess(%s)', [AExeName]));
6. {$IFDEF MSWINDOWS}
7.   DebugLn(Format('RunCommand=%d', [Ord(RunCommand('taskkill', ['/f', '/im', AExeName], LStr))]));
8. {$ELSE}
9. {$IFDEF LINUX}
10.   DebugLn(Format('RunCommand=%d', [Ord(RunCommand('killall', [AExeName], LStr))]));
11. {$ELSE}
12. {$ENDIF}
13. {$ENDIF}
14. end;
15.  

Maybe there are better solutions, but... it works. 

[balazsszekely]

@jaz2014

Iwant to be able to force closure of the child shell (killing ffmpeg obviously) but cant seem
to see how to do that.
Ideally I want to do it whether I have a console window open or not.

I've tried windows messaging and everything else I can find here but nothing seems
to reference killing a child program.

Can anyone tell me the simplest way to do his ?

Your application is the parent process. Iterate through all processes, compare each process parent id with your application process id. If there is a match, you found cmd.ex.  Do the same for cmd to find ffmpeg. Something like this(not tested):

Code: Pascal  [Select][+][-]

1. function FindProcessByParentID(const AParentID: DWORD): DWORD;
2. var
3.   Proc: TPROCESSENTRY32;
4.   hSnap: HWND;
5.   Looper: BOOL;
6. begin
7.   Result := 0;
8.   Proc.dwSize := SizeOf(Proc);
9.   hSnap := CreateToolhelp32Snapshot(TH32CS_SNAPALL, 0);
10.   Looper := Process32First(hSnap, Proc);
11.   while Integer(Looper) <> 0 do
12.   begin
13.     if Proc.th32ParentProcessID = AParentID then
14.     begin
15.       Result := Proc.th32ProcessID;
16.       Break;
17.     end;
18.     Looper := Process32Next(hSnap, Proc);
19.   end;
20.   CloseHandle(hSnap);
21. end;
22.  
23. function KillProcess(const AProcessID: DWORD): Boolean;
24. var
25.   ProcHandle: THandle;
26. begin
27.   Result := False;
28.   ProcHandle := OpenProcess(PROCESS_TERMINATE, False, AProcessID);
29.   if ProcHandle > 0 then
30.   try
31.     Result := TerminateProcess(ProcHandle, 0);
32.   finally
33.     CloseHandle(ProcHandle);
34.   end;
35. end;
36.  
37. procedure TForm1.Button1Click(Sender: TObject);
38. var
39.   CmdID: DWord;
40.   FfmpegID: DWord;
41. begin
42.   CmdID := FindProcessByParentID(GetCurrentProcessId);
43.   if CmdID > 0 then
44.   begin
45.     FfmpegID := FindProcessByParentID(CmdID);
46.     if FfmpegID > 0 then
47.       KillProcess(FfmpegID);
48.     KillProcess(CmdID); //if needed
49.   end;
50. end;  

[jaz2014]

I have to say those are the 2 most pleasing responses I think I've had in any forum for a long time.
Thank you both.

I'm going with GetMem's functions as they are probably safer and more comprehensive
for use in my application (which is getting a bit complex)

I'd never heard of createtoolhelp32snapshot or (as I've discovered) jwaTLHelp32 before and thought
they were some sort of commercial tools I couldnt find anywhere when I saw them in the wiki !
Lazarus docs cripple me once again...

GetMem you'll be pleased to know I did a simple cut and paste to relevant places
and it all worked first time - no changes needed.
(Impressive given the issue)

A double thanks for taking the trouble to use my program names  - a very nice helpful touch.
I'm guessing I can find more uses for this - it's a shame it coldn't be built into TProcess
to do other things with child situations

Anyway thats got me out of that hole - now to go dig another ...

Thank you both
jaz