delphi 问题~~~winexec 想了好久想不明白

Question

procedure TForm1.Button3Click(Sender: TObject);
begin 
 str1:='cmd.exe /c dir/b/a '+Combobox1.Text+'>c:\dir.txt'  ;
  winexec(pchar(str1),SW_HIDE);
  listbox1.Clear;
  listbox1.Items.LoadFromFile('c:\dir.txt');
end;为什么要单击按钮两下，列表框内的内容才能正确显示？？？

Answer 1

因为winexec不等待cmd执行完就返回了

Answer 2

function WinExecAndWait32(FileName : PChar; CommandLine : PChar;
                          Visibility : Integer) : Integer;
 { returns -1 if the Exec failed, otherwise returns the process' exit
   code when the process terminates }
var
  zAppName:array[0..512] of char;
  zCurDir:array[0..255] of char;
  WorkDir:ShortString;
  StartupInfo:TStartupInfo;
  ProcessInfo:TProcessInformation;
  Temp : DWORD;
begin
  StrCopy(zAppName, FileName);
  StrCat(zAppName, CommandLine);
  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 }
      false,                         { handle inheritance flag }
      CREATE_NEW_CONSOLE or          { creation flags }
      NORMAL_PRIORITY_CLASS,
      nil,                           { pointer to new environment block }
      nil,                           { pointer to current directory name }
      StartupInfo,                   { pointer to STARTUPINFO }
      ProcessInfo) then              { pointer to PROCESS_INF }
    Result := -1
  else begin
    WaitforSingleObject(ProcessInfo.hProcess,INFINITE);
    GetExitCodeProcess(ProcessInfo.hProcess,Temp);
    Result := Integer(Temp);                                      
  end;
end;
///////////////
WinExecAndWait32(pchar(str1),nil,SW_HIDE);