Delphi procedure execute program with more than 512 chars

Question

I need to call an external program from Delphi 2006 code with a long list of arguments, specifically to concatenate mutiple PDFs into one file using PDFTK. The full string to be executed has over 512 characters, but both WinExec and ShellExecute have a 512 character limit.

Are there any alternatives to these procedures that have much larger limits?

Answer 1

Just found this @SwissDelphiCentre, which seems to work nicely:

procedure ShellExecute_AndWait(FileName: string; Params: string);
var
  exInfo: TShellExecuteInfo;
  Ph: DWORD;
begin
  FillChar(exInfo, SizeOf(exInfo), 0);
  with exInfo do
  begin
    cbSize := SizeOf(exInfo);
    fMask := SEE_MASK_NOCLOSEPROCESS or SEE_MASK_FLAG_DDEWAIT;
    Wnd := GetActiveWindow();
    ExInfo.lpVerb := 'open';
    ExInfo.lpParameters := PChar(Params);
    lpFile := PChar(FileName);
    nShow := SW_SHOWNORMAL;
  end;
  if ShellExecuteEx(@exInfo) then
    Ph := exInfo.HProcess
  else
  begin
    ShowMessage(SysErrorMessage(GetLastError));
    Exit;
  end;
  while WaitForSingleObject(ExInfo.hProcess, 50) <> WAIT_OBJECT_0 do
    Application.ProcessMessages;
  CloseHandle(Ph);
end;

Answer 2

Just use a temporary BATCH file, containing the commands to be executed.

This will allow also some enhanced features, like calling several PDFTK instance in a row, add backup or copy of files, just in the same process.

Run the batch as SW_SHOWMINIMIZED to have no black console window pop up.

Answer 3

There are some limits on the length of the names passed to ShellExecute, but these are typically greater than 512 characters. It seems you just need to dynamically allocate the names rather than using a static char array.

If you want to go to the ultimate command line length then you can use CreateProcess which has a limit of 32,768 characters.

As another option you could consider writing the list of arguments to a temporary file. Then you would modify the external program so that it is capable of being passed the path to that file as its command line argument. You would obviously need to also modify the external program so that it could read the file and obtain the long list of files from the temporary file.