ReadDirectoryChangesW (windows)

Ognen Duzlevski maketo at
Mon Jan 26 04:29:39 CET 2004

Hi all,

I am new to win32 programming and was wondring if anyone can enlighten me on a question I have:

there is a win32file function I would like to use - ReadDirectoryChangesW() and its parameters are, according to

ReadDirectoryChangesW(handle, size, bWatchSubtree, dwNotifyFilter, overlapped)

retrieves information describing the changes occurring within a directory.


handle : int
Handle to the directory to be monitored. This directory must be opened with the FILE_LIST_DIRECTORY access right.

size : int
Size of the buffer to allocate for the results.

bWatchSubtree : int
Specifies whether the ReadDirectoryChangesW function will monitor the directory or the directory tree. If TRUE is 
specified, the function monitors the directory tree rooted at the specified directory. If FALSE is specified, the 
function monitors only the directory specified by the hDirectory parameter.

dwNotifyFilter : int
Specifies filter criteria the function checks to determine if the wait operation has completed. This parameter can be 
one or more of the FILE_NOTIFY_CHANGE_* values.

overlapped=None : PyOVERLAPPED
Must be None

I would like to use this function asynchronously to open a directory using the FILE_FLAG_OVERLAPPED flag so that I can 
later on wait for a change to be signalled and so that I can use this in a service waiting with e.g. 

I don't have much experience using pywin32 and I am puzzled by the last line "Must be None". Does this mean 
asynchronous access is not supported? Or am I ready to actually RTFM if someone can politely point me to one? :)


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