uses
  Controls, Windows, SysUtils, Forms;

{---------------------------CreateDOSProcessRedirected--------------------------
 Description    : executes a (DOS!) app defined in the CommandLine parameter
                  redirected to take input from InputFile (optional) and give
                  output to OutputFile
 Result         : True on success
 Parameters     : CommandLine : the command line for app, including full path
                  InputFile   : the ascii file where from the app takes input,
                                 empty if no input needed/required.
                  OutputFile  : the ascii file to which the output is redirected
                  ErrMsg      : additional error message string. Can be empty
 Error checking : YES
 Target         : Delphi 2, 3, 4
 Author         : Theodoros Bebekis, email bebekis@otenet.gr
 Notes          :
 Example call   : CreateDOSProcessRedirected('C:\MyDOSApp.exe',
                                             'C:\InputPut.txt',
                                             'C:\OutPut.txt',
                                             'Please, record this message')
-------------------------------------------------------------------------------}
function CreateDOSProcessRedirected(const CommandLine, InputFile, OutputFile,
   ErrMsg :string): boolean;
const
  ROUTINE_ID = '[function: CreateDOSProcessRedirected]';
var
  OldCursor     : TCursor;
  pCommandLine  : array[0..MAX_PATH] of char;
  pInputFile,
  pOutPutFile   : array[0..MAX_PATH] of char;
  StartupInfo   : TStartupInfo;
  ProcessInfo   : TProcessInformation;
  SecAtrrs      : TSecurityAttributes;
  hAppProcess,
  hAppThread,
  hInputFile,
  hOutputFile   : THandle;
begin
  Result := FALSE;

  { check for InputFile existence }
  if (InputFile <> '') and (not FileExists(InputFile)) then
    raise Exception.CreateFmt(ROUTINE_ID + #10 + #10 +
       'Input file * %s *' + #10 +
       'does not exist' + #10 + #10 +
       ErrMsg, [InputFile]);

  hAppProcess := 0;
  hAppThread := 0;
  hInputFile := 0;
  hOutputFile := 0;

  { save the cursor }
  OldCursor     := Screen.Cursor;
  Screen.Cursor := crHourglass;

  try
    { copy the parameter Pascal strings to null terminated strings }
    StrPCopy(pCommandLine, CommandLine);
    StrPCopy(pInputFile, InputFile);
    StrPCopy(pOutPutFile, OutputFile);

    { prepare SecAtrrs structure for the CreateFile calls.  This SecAttrs
      structure is needed in this case because we want the returned handle to
      be inherited by child process. This is true when running under WinNT.
      As for Win95, the parameter is ignored. }
    FillChar(SecAtrrs, SizeOf(SecAtrrs), #0);
    SecAtrrs.nLength              := SizeOf(SecAtrrs);
    SecAtrrs.lpSecurityDescriptor := nil;
    SecAtrrs.bInheritHandle       := TRUE;

    if InputFile <> '' then
    begin
      { create the appropriate handle for the input file }
      hInputFile := CreateFile(
         pInputFile,                          { pointer to name of the file }
         GENERIC_READ or GENERIC_WRITE,       { access (read-write) mode }
         FILE_SHARE_READ or FILE_SHARE_WRITE, { share mode }
         @SecAtrrs,                           { pointer to security attributes }
         OPEN_ALWAYS,                         { how to create }
         FILE_ATTRIBUTE_NORMAL
         or FILE_FLAG_WRITE_THROUGH,          { file attributes }
         0);                                 { handle to file with attrs to copy }

      { is hInputFile a valid handle? }
      if hInputFile = INVALID_HANDLE_VALUE then
        raise Exception.CreateFmt(ROUTINE_ID + #10 +  #10 +
           'WinApi function CreateFile returned an invalid handle value' + #10 +
           'for the input file * %s *' + #10 + #10 +
            ErrMsg, [InputFile]);
    end else
      { we aren't using an input file }
      hInputFile := 0;

    { create the appropriate handle for the output file }
    hOutputFile := CreateFile(
       pOutPutFile,                         { pointer to name of the file }
       GENERIC_READ or GENERIC_WRITE,       { access (read-write) mode }
       FILE_SHARE_READ or FILE_SHARE_WRITE, { share mode }
       @SecAtrrs,                           { pointer to security attributes }
       CREATE_ALWAYS,                       { how to create }
       FILE_ATTRIBUTE_NORMAL
       or FILE_FLAG_WRITE_THROUGH,          { file attributes }
       0 );                                 { handle to file with attrs to copy }

    { is hOutputFile a valid handle? }
    if hOutputFile = INVALID_HANDLE_VALUE then
      raise Exception.CreateFmt(ROUTINE_ID + #10 +  #10 +
         'WinApi function CreateFile returned an invalid handle value'  + #10 +
         'for the output file * %s *' + #10 + #10 +
         ErrMsg, [OutputFile]);

    { prepare StartupInfo structure }
    FillChar(StartupInfo, SizeOf(StartupInfo), #0);
    StartupInfo.cb          := SizeOf(StartupInfo);
    StartupInfo.dwFlags     := STARTF_USESHOWWINDOW or STARTF_USESTDHANDLES;
    StartupInfo.wShowWindow := SW_HIDE;
    StartupInfo.hStdOutput  := hOutputFile;
    StartupInfo.hStdInput   := hInputFile;

    { create the app }
    Result := CreateProcess(
       NIL,                           { pointer to name of executable module }
       pCommandLine,                  { pointer to command line string }
       NIL,                           { pointer to process security attributes }
       NIL,                           { pointer to thread security attributes }
       TRUE,                          { handle inheritance flag }
       HIGH_PRIORITY_CLASS,           { creation flags }
       NIL,                           { pointer to new environment block }
       NIL,                           { pointer to current directory name }
       StartupInfo,                   { pointer to STARTUPINFO }
       ProcessInfo);                  { pointer to PROCESS_INF }

    { wait for the app to finish its job and take the handles to free them later }
    if Result then
    begin
      WaitforSingleObject(ProcessInfo.hProcess, INFINITE);
      hAppProcess  := ProcessInfo.hProcess;
      hAppThread   := ProcessInfo.hThread;
    end else
      raise Exception.Create(ROUTINE_ID + #10 +  #10 +
         'Function failure'  + #10 +  #10 + ErrMsg);

  finally
    { close the handles
      Kernel objects, like the process and the files we created in this case,
      are maintained by a usage count.
      So, for cleaning up purposes we have to close the handles
      to inform the system that we don't need the objects anymore }
    if hOutputFile <> 0 then
      CloseHandle(hOutputFile);
    if hInputFile <> 0 then
      CloseHandle(hInputFile);
    if hAppThread <> 0 then
      CloseHandle(hAppThread);
    if hAppProcess <> 0 then
      CloseHandle(hAppProcess);
    { restore the old cursor }
    Screen.Cursor:= OldCursor;
  end;
end;    { CreateDOSProcessRedirected }