Question

Given an absolute file system path, how would I detect whether it’s on an NTFS partition or not? I would prefer a helping hand in C#, but Win32/C would do. The system which the software will run on, is Windows Vista or later.

Answer 1

You can use FSCTL_FILESYSTEM_GET_STATISTICS to determine the file system type.

Here’s some sample code. I’ve checked that this handles mount points properly, i.e., it detects the type of the target volume, not the source volume. You don’t need to specify the mount point itself (although you can) but the file or directory you specify must exist.

#define _WIN32_WINNT 0x0502

#include <windows.h>

#include <stdio.h>

int wmain(int argc, wchar_t ** argv)
{
    HANDLE h;
    FILESYSTEM_STATISTICS * fs;
    BYTE buffer[32768];
    DWORD dw;

    h = CreateFile(argv[1], 0, 
        FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, 
        NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);

    if (h == INVALID_HANDLE_VALUE)
    {
        printf("CreateFile: %u\n", GetLastError());
        return 1;
    }

    if (!DeviceIoControl(h, FSCTL_FILESYSTEM_GET_STATISTICS, NULL, 0, buffer, sizeof(buffer), &dw, NULL))
    {
        dw = GetLastError();
        CloseHandle(h);
        printf("DeviceIoControl: %u\n", dw);
        if (dw == ERROR_INVALID_FUNCTION)
        {
            printf("This probably means the specified file or directory is not on an NTFS volume.\n");
            printf("For example, this happens if you specify a file on a CD-ROM.\n");
        }
        return 1;
    }

    CloseHandle(h);

    fs = (FILESYSTEM_STATISTICS *)buffer;
    printf("Filesystem type: %u\n", fs->FileSystemType);

    if (fs->FileSystemType == FILESYSTEM_STATISTICS_TYPE_NTFS)
    {
        printf("The file or directory is on an NTFS volume.\n");
    }
    else
    {
        printf("The file or directory is not on an NTFS volume.\n");
    }
    return 0;
}