取得目錄變更通知

應用程式可以使用變更通知來監視目錄及其子目錄的內容。 等候變更通知類似於對目錄進行擱置的讀取作業，並視需要等候其子目錄。 當目錄內發生變更時，讀取作業就會完成。 例如，每當受監視目錄內的檔名變更時，應用程式就可以使用這些函式來更新目錄清單。

應用程式可以使用 FindFirstChangeNotification 函式來指定觸發變更通知的一組條件。 這些條件包括檔名、目錄名稱、屬性、檔案大小、上次寫入時間和安全性的變更。 此函式也會傳回可以使用等候函式等候的句柄。 如果滿足等候條件， FindNextChangeNotification 可用來提供通知句柄，以等候後續的變更。 不過，這些函式不會指出符合等候條件的實際變更。

使用 FindCloseChangeNotification 關閉通知句柄。

若要擷取通知中特定變更的相關信息，請使用 ReadDirectoryChangesW 函式。 此函式也可讓您提供完成例程。

若要追蹤磁碟區上的變更，請參閱 變更日誌。

下列範例會監視目錄樹狀目錄的名稱變更。 它也會監視目錄的檔名變更。 此範例會使用 FindFirstChangeNotification 函式來建立兩個通知句柄，以及 WaitForMultipleObjects 函式在句柄上等候。 每當樹狀結構中建立或刪除目錄時，範例應該更新整個目錄樹狀結構。 每當目錄中建立或刪除檔案時，範例應該會重新整理目錄。

#include <windows.h>
#include <stdlib.h>
#include <stdio.h>
#include <tchar.h>

void RefreshDirectory(LPTSTR);
void RefreshTree(LPTSTR);
void WatchDirectory(LPTSTR);

void _tmain(int argc, TCHAR *argv[])
{
    if(argc != 2)
    {
        _tprintf(TEXT("Usage: %s <dir>\n"), argv[0]);
        return;
    }

    WatchDirectory(argv[1]);
}

void WatchDirectory(LPTSTR lpDir)
{
   DWORD dwWaitStatus; 
   HANDLE dwChangeHandles[2]; 
   TCHAR lpDrive[4];
   TCHAR lpFile[_MAX_FNAME];
   TCHAR lpExt[_MAX_EXT];

   _tsplitpath_s(lpDir, lpDrive, 4, NULL, 0, lpFile, _MAX_FNAME, lpExt, _MAX_EXT);

   lpDrive[2] = (TCHAR)'\\';
   lpDrive[3] = (TCHAR)'\0';
 
// Watch the directory for file creation and deletion. 
 
   dwChangeHandles[0] = FindFirstChangeNotification( 
      lpDir,                         // directory to watch 
      FALSE,                         // do not watch subtree 
      FILE_NOTIFY_CHANGE_FILE_NAME); // watch file name changes 
 
   if (dwChangeHandles[0] == INVALID_HANDLE_VALUE) 
   {
     printf("\n ERROR: FindFirstChangeNotification function failed.\n");
     ExitProcess(GetLastError()); 
   }
 
// Watch the subtree for directory creation and deletion. 
 
   dwChangeHandles[1] = FindFirstChangeNotification( 
      lpDrive,                       // directory to watch 
      TRUE,                          // watch the subtree 
      FILE_NOTIFY_CHANGE_DIR_NAME);  // watch dir name changes 
 
   if (dwChangeHandles[1] == INVALID_HANDLE_VALUE) 
   {
     printf("\n ERROR: FindFirstChangeNotification function failed.\n");
     ExitProcess(GetLastError()); 
   }
 

// Make a final validation check on our handles.

   if ((dwChangeHandles[0] == NULL) || (dwChangeHandles[1] == NULL))
   {
     printf("\n ERROR: Unexpected NULL from FindFirstChangeNotification.\n");
     ExitProcess(GetLastError()); 
   }

// Change notification is set. Now wait on both notification 
// handles and refresh accordingly. 
 
   while (TRUE) 
   { 
   // Wait for notification.
 
      printf("\nWaiting for notification...\n");

      dwWaitStatus = WaitForMultipleObjects(2, dwChangeHandles, 
         FALSE, INFINITE); 
 
      switch (dwWaitStatus) 
      { 
         case WAIT_OBJECT_0: 
 
         // A file was created, renamed, or deleted in the directory.
         // Refresh this directory and restart the notification.
 
             RefreshDirectory(lpDir); 
             if ( FindNextChangeNotification(dwChangeHandles[0]) == FALSE )
             {
               printf("\n ERROR: FindNextChangeNotification function failed.\n");
               ExitProcess(GetLastError()); 
             }
             break; 
 
         case WAIT_OBJECT_0 + 1: 
 
         // A directory was created, renamed, or deleted.
         // Refresh the tree and restart the notification.
 
             RefreshTree(lpDrive); 
             if (FindNextChangeNotification(dwChangeHandles[1]) == FALSE )
             {
               printf("\n ERROR: FindNextChangeNotification function failed.\n");
               ExitProcess(GetLastError()); 
             }
             break; 
 
         case WAIT_TIMEOUT:

         // A timeout occurred, this would happen if some value other 
         // than INFINITE is used in the Wait call and no changes occur.
         // In a single-threaded environment you might not want an
         // INFINITE wait.
 
            printf("\nNo changes in the timeout period.\n");
            break;

         default: 
            printf("\n ERROR: Unhandled dwWaitStatus.\n");
            ExitProcess(GetLastError());
            break;
      }
   }
}

void RefreshDirectory(LPTSTR lpDir)
{
   // This is where you might place code to refresh your
   // directory listing, but not the subtree because it
   // would not be necessary.

   _tprintf(TEXT("Directory (%s) changed.\n"), lpDir);
}

void RefreshTree(LPTSTR lpDrive)
{
   // This is where you might place code to refresh your
   // directory listing, including the subtree.

   _tprintf(TEXT("Directory tree (%s) changed.\n"), lpDrive);
}