Retrieves the length of the specified disk, volume, or partition.

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

BOOL DeviceIoControl(
  (HANDLE) hDevice,             // handle to device
  IOCTL_DISK_GET_LENGTH_INFO,   // 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


Volume handles do not have access to the full volume. To read or write to the last few sectors of a volume, you must call FSCTL_ALLOW_EXTENDED_DASD_IO, which instructs the file system to not perform any boundary checks.

This operation should be used instead of IOCTL_DISK_GET_PARTITION_INFO_EX for volumes that do not have partition info—such as partition type or number of hidden sectors.


Requirement Value
Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Header winioctl.h (include Windows.h)

See also