Getting the cluster size of a hard drive (through code)

Question

I need to find the cluster size of the users hard drive, through C or C++. The hard drive uses NTFS (though I'd appreciate knowing how it's done on other file systems as well).

I guess what I need is some combination of win32 API calls, but I don't know which.

For instance, typing "fsutil fsinfo ntfsinfo c:" in the windows console gives you "Bytes per cluster", which is what I need. (Though for obvious reasons, I don't want to run that command and parse it's output.)

Keep in mind that this doesn't tell you a whole lot. Small files can be stored in the directory node itself. — MSalters, Jul 02 '09 at 15:25
FWIW, a file system's cluster size is sometimes also referred to as its "allocation unit" size, e.g.: http://msdn.microsoft.com/en-us/library/aa383356(VS.85).aspx. — reuben, Jul 05 '09 at 08:17

score 17 · Accepted Answer · answered Jul 02 '09 at 10:39

Use the GetDiskFreeSpace

BOOL WINAPI GetDiskFreeSpace(
  __in   LPCTSTR lpRootPathName,
  __out  LPDWORD lpSectorsPerCluster, // <--
  __out  LPDWORD lpBytesPerSector, // <--
  __out  LPDWORD lpNumberOfFreeClusters,
  __out  LPDWORD lpTotalNumberOfClusters
);

Getting the cluster size of a hard drive (through code)

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