Checking for open files in a given directory tree

Question

Is there a way to determine with C+++ if any file is open in a given directory tree?

Cmd.exe knows instantly if I attempt to rename a folder and a file within that directory tree is currently open. I've used API Monitor to determine that cmd.exe uses NtOpenFile() followed by NtSetInformationFile with FileRenameInformation and that returns STATUS_ACCESS_DENIED when a file is open but I've not been able to determine what's happening at a lower level.

I'm trying to ensure no files are open before beginning a batch process without having to check each file individually as there could be hundreds of thousands of files in the directory tree.

Can anyone expand on this?

Thanks, Steve Thresher.

Answer 1

You will have to check each file individually, I think. That said, this should do it:

HANDLE hFile = CreateFile
    (my_filename, GENERIC_READ, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

if (hFile == INVALID_HANDLE_VALUE)
{
    DWORD err = GetLastError ();
    if (err == ERROR_SHARING_VIOLATION)
    {
        // File is already open
    }
}
else
    CloseHandle (hFile);

Note that dwShareMode is passed as 0, which prevents Windows opening the file if it is already opened elsewhere.