Synchronously-launching-an-application


            Title: Synchronously launching an application
Question: How to run a program and wait for it to terminate ?
Answer:
 Here two methods of running another application and waiting for it to terminate (as opposed to ShellExecute, which only starts the specified program, and returns immediately).
{the code speaks for itself, but try to look up API functions you don't recognize}
{the first example, based on WaitForSingleObject}
function WinExecAndWait32_v1(FileName: string; Visibility: integer):
Cardinal; {integer}
var
 zAppName: array[0..512] of char;
 zCurDir: array[0..255] of char;
 WorkDir: string;
 StartupInfo: TStartupInfo;
 ProcessInfo: TProcessInformation;
begin
 StrPCopy(zAppName, FileName);
 GetDir(0, WorkDir);
 StrPCopy(zCurDir, WorkDir);
 FillChar(StartupInfo, Sizeof(StartupInfo), #0);
 StartupInfo.cb := Sizeof(StartupInfo);
 StartupInfo.dwFlags := STARTF_USESHOWWINDOW;
 StartupInfo.wShowWindow := Visibility;
 if not CreateProcess(nil,
 zAppName, { pointer to command line string }
 nil, { pointer to process security attributes }
 nil, { pointer to thread security attributes }
 true, { handle inheritance flag }
 CREATE_NEW_CONSOLE or { creation flags }
 NORMAL_PRIORITY_CLASS,
 nil, { pointer to new environment block }
 nil, { pointer to current directory name, PChar}
 StartupInfo, { pointer to STARTUPINFO }
 ProcessInfo) { pointer to PROCESS_INF }
 then Result := INFINITE {-1} else
 begin
 WaitforSingleObject(ProcessInfo.hProcess, INFINITE);
 GetExitCodeProcess(ProcessInfo.hProcess, Result);
 CloseHandle(ProcessInfo.hProcess); { to prevent memory leaks }
 CloseHandle(ProcessInfo.hThread);
 end;
end;
 
{the second example, based on PeekMessage(msg,,,,PM_REMOVE)-DispatchMessage(msg)}
function WinExecAndWait32_v2(FileName: string; Visibility: integer):
Cardinal; {integer}
var
 zAppName: array[0..512] of char;
 zCurDir: array[0..255] of char;
 WorkDir: string;
 StartupInfo: TStartupInfo;
 ProcessInfo: TProcessInformation;
 Msg: TagMsg;
 ExitCode: cardinal;
begin
 StrPCopy(zAppName, FileName);
 GetDir(0, WorkDir);
 StrPCopy(zCurDir, WorkDir);
 FillChar(StartupInfo, Sizeof(StartupInfo), #0);
 StartupInfo.cb := Sizeof(StartupInfo);
 StartupInfo.dwFlags := STARTF_USESHOWWINDOW; // STARTF_FORCEONFEEDBACK;
 StartupInfo.wShowWindow := Visibility;
 if CreateProcess(nil, { and once more: }
 zAppName, { pointer to command line string }
 nil, { pointer to process security attributes }
 nil, { pointer to thread security attributes }
 false, { handle inheritance flag }
 NORMAL_PRIORITY_CLASS, { creation flags }
 nil, { pointer to the new environment block }
 nil, { current directory name }
 StartupInfo, { pointer to STARTUPINFO }
 ProcessInfo) then { pointer to PROCESS_INF }
 begin
 repeat
 while PeekMessage(Msg, 0, 0, 0, PM_REMOVE) do
 begin
 if (Msg.message = WM_QUIT) then
 Result := Msg.wParam;
 TranslateMessage(msg);
 Dispatchmessage(msg);
 Sleep(100); {your choice}
 end;
 GetExitCodeProcess(ProcessInfo.hProcess, ExitCode);
 until (ExitCode STILL_ACTIVE);
 CloseHandle(ProcessInfo.hThread);
 CloseHandle(ProcessInfo.hProcess);
 Result := 0;
 end
 else begin
 Result := GetLastError;
 end;
end;
 
Bogdan Grigorescu - BogdanG@gmail.com
BG Remote Programming Group
Examples Delphi
