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关于C ++：如何查看目录的子文件是否已更改

2023-04-14 23:41:00

How to see if a subfile of a directory has changed

在Windows中，是否有一种简单的方法来判断文件夹是否具有已更改的子文件？

我已验证，并且子文件更改时，文件夹上的上次修改日期不会更新。

我可以设置一个注册表项来修改此行为吗？

如果有关系，我正在使用NTFS卷。

我最终希望在C ++程序中具有此功能。

由于文件夹太大，因此无法递归扫描整个目录。

更新：我真的需要一种方法来在更改发生时不运行任何进程来执行此操作。因此，安装文件系统监视程序对我而言不是最佳选择。

Update2：存档位也将不起作用，因为它与上次修改日期存在相同的问题。将设置文件的存档位，但不会设置文件夹。

本文应该有所帮助。基本上，您创建一个或多个通知对象，例如：

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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());
}

然后您等待通知：

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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;
}
}
}

也许这是矫kill过正，但MS的IFS套件或OSR的FDDK可能是替代方案。通过简单监视文件系统的所有更改来创建自己的文件系统过滤器驱动程序。

ReadDirectoryChangesW

此CodeProject文章中的一些出色的示例代码

也许您可以将NTFS 5 Change Journal与DeviceIoControl结合使用，如此处所述

如果更改发生后您无法运行某个进程，那么除了扫描文件系统并检查修改日期/时间之外，您无能为力。但是，这需要您存储每个文件的最后日期/时间并进行比较。

您可以使用存档位来加快速度(尽管它可能会使备份软件混乱，因此请谨慎操作)。

An archive bit is a file attribute
present in many computer file systems,
notably FAT, FAT32, and NTFS. The
purpose of an archive bit is to track
incremental changes to files for the
purpose of backup, also called
archiving.

As the archive bit is a binary bit, it
is either 1 or 0, or in this case more
frequently called set (1) and clear
(0). The operating system sets the
archive bit any time a file is
created, moved, renamed, or otherwise
modified in any way. The archive bit
therefore represents one of two
states:"changed" and"not changed"
since the last backup.

Archive bits are not affected by
simply reading a file. When a file is
copied, the original file's archive
bit is unaffected, however the copy's
archive bit will be set at the time
the copy is made.