FSCTL_FILESYSTEM_GET_STATISTICS control code

Retrieves the information from various file system performance counters.

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

BOOL DeviceIoControl(
  (HANDLE) hDevice,                 // handle to device
  FSCTL_FILESYSTEM_GET_STATISTICS,  // 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
);

Parameters

hDevice

A handle to the file or directory from which the object identifier is to be retrieved. To retrieve a device handle, call the CreateFile function.

dwIoControlCode

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

lpInBuffer

Not used with this operation; set to NULL.

nInBufferSize

Not used with this operation; set to zero.

lpOutBuffer

A pointer to the output buffer, a FILESYSTEM_STATISTICS structure.

nOutBufferSize

The size of the output buffer, in bytes.

lpBytesReturned

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.

lpOverlapped

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.

If the operation fails or is pending, DeviceIoControl returns zero. To get extended error information, call GetLastError.

A return value from GetLastError of ERROR_MORE_DATA indicates to the caller that the buffer was not large enough to accommodate all the requested data. In this event, you can make subsequent FSCTL_FILESYSTEM_GET_STATISTICS calls to retrieve the remaining data.

Remarks

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

Requirements

See also

CreateFile

DeviceIoControl

File Management Control Codes

FILESYSTEM_STATISTICS

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Build date: 4/16/2013