c++ - How to see if a subfile of a directory has changed

Question

In Windows, is there an easy way to tell if a folder has a subfile that has changed?

I verified, and the last modified date on the folder does not get updated when a subfile changes.

Is there a registry entry I can set that will modify this behavior?

If it matters, I am using an NTFS volume.

I would ultimately like to have this ability from a C++ program.

Scanning an entire directory recursively will not work for me because the folder is much too large.

Update: I really need a way to do this without a process running while the change occurs. So installing a file system watcher is not optimal for me.

Update2: The archive bit will also not work because it has the same problem as the last modification date. The file's archive bit will be set, but the folders will not.

Answer 1

This article should help. Basically, you create one or more notification object such as:

HANDLE dwChangeHandles[2]; 
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("
 ERROR: FindFirstChangeNotification function failed.
");
     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("
 ERROR: FindFirstChangeNotification function failed.
");
     ExitProcess(GetLastError()); 
   }

and then you wait for a notification:

 while (TRUE) 
   { 
   // Wait for notification. 
      printf("
Waiting for notification...
");

      DWORD dwWaitStatus = WaitForMultipleObjects(2, dwChangeHandles, 
         FALSE, INFINITE); 

      switch (dwWaitStatus) 
      { 
         case WAIT_OBJECT_0: 

         // A file was created, renamed, or deleted in the directory.
         // Restart the notification. 
             if ( FindNextChangeNotification(dwChangeHandles[0]) == FALSE )
             {
               printf("
 ERROR: FindNextChangeNotification function failed.
");
               ExitProcess(GetLastError()); 
             }
             break; 

         case WAIT_OBJECT_0 + 1: 

         // Restart the notification. 
             if (FindNextChangeNotification(dwChangeHandles[1]) == FALSE )
             {
               printf("
 ERROR: FindNextChangeNotification function failed.
");
               ExitProcess(GetLastError()); 
             }
             break; 

         case WAIT_TIMEOUT:

         // A time-out 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("
No changes in the time-out period.
");
            break;

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