Retrieves the reparse point data associated with the file or directory identified by the specified handle.

To perform this operation, call the DeviceIoControl function with the following parameters.

BOOL DeviceIoControl(
  (HANDLE) hDevice,            // handle to file or directory
  FSCTL_GET_REPARSE_POINT,     // dwIoControlCode
  NULL,                        // lpInBuffer
  0,                           // nInBufferSize
  (LPVOID) lpOutBuffer,        // output buffer
  (DWORD) nOutBufferSize,      // size of output buffer
  (LPDWORD) lpBytesReturned,   // number of bytes returned
  (LPOVERLAPPED) lpOverlapped  // OVERLAPPED structure



A handle to the file or directory from which to retrieve the reparse point data. To retrieve a handle, use the CreateFile function.


The control code for the operation. Use FSCTL_GET_REPARSE_POINT for this operation.


Not used with this operation; set to NULL.


Not used with this operation; set to zero.


A pointer to a buffer that receives the reparse point data. If the reparse tag is a Microsoft reparse tag, the data is a REPARSE_DATA_BUFFER structure. Otherwise, the data is a REPARSE_GUID_DATA_BUFFER structure.


The size of the output buffer, in bytes. This value must be at least the size indicated by REPARSE_GUID_DATA_BUFFER_HEADER_SIZE, plus the size of the expected user-defined data.


A pointer to a variable that receives the size of the data stored in the output buffer, in bytes.

If the output buffer is too small, the call fails, GetLastError returns ERROR_INSUFFICIENT_BUFFER, and lpBytesReturned is zero.

If lpOverlapped is NULL, lpBytesReturned cannot be NULL. Even when an operation returns no output data and lpOutBuffer is NULL, DeviceIoControl makes use of lpBytesReturned. After such an operation, the value of lpBytesReturned is meaningless.

If lpOverlapped is not NULL, lpBytesReturned can be NULL. If this parameter is not NULL and the operation returns data, lpBytesReturned is meaningless until the overlapped operation has completed. To retrieve the number of bytes returned, call GetOverlappedResult. If hDevice is associated with an I/O completion port, you can retrieve the number of bytes returned by calling GetQueuedCompletionStatus.


A pointer to an OVERLAPPED structure.

If hDevice was opened without specifying FILE_FLAG_OVERLAPPED, lpOverlapped is ignored.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, the operation is performed as an overlapped (asynchronous) operation. In this case, lpOverlapped must point to a valid OVERLAPPED structure that contains a handle to an event object. Otherwise, the function fails in unpredictable ways.

For overlapped operations, DeviceIoControl returns immediately, and the event object is signaled when the operation has been completed. Otherwise, the function does not return until the operation has been completed or an error occurs.

Return value

If the operation completes successfully, DeviceIoControl returns a nonzero value, and the output buffer pointed to by lpOutBuffer contains a valid REPARSE_GUID_DATA_BUFFER structure, or a portion thereof, depending on the value of nOutBufferSize.

If the operation fails or is pending, DeviceIoControl returns zero. The contents of the output buffer pointed to by lpOutBuffer are meaningless. For extended error information, call GetLastError.


For the implications of overlapped I/O on this operation, see the Remarks section of DeviceIoControl.

In Windows 8 and Windows Server 2012, this code is supported by the following technologies.


Server Message Block (SMB) 3.0 protocol


SMB 3.0 Transparent Failover (TFO)


SMB 3.0 with Scale-out File Shares (SO)


Cluster Shared Volume File System (CsvFS)


Resilient File System (ReFS)



CsvFs does not support reparse points.


Minimum supported client

Windows XP [desktop apps only]

Minimum supported server

Windows Server 2003 [desktop apps only]


WinIoCtl.h (include Windows.h)

See also

Reparse Points