Header: Dir Entry

struct msdos_dir_entry {
        __u8    name[MSDOS_NAME];/* name and extension */
        __u8    attr;           /* attribute bits */
        __u8    lcase;          /* Case for base and extension */
        __u8    ctime_cs;       /* Creation time, centiseconds (0-199) */
        __le16  ctime;          /* Creation time */
        __le16  cdate;          /* Creation date */
        __le16  adate;          /* Last access date */
        __le16  starthi;        /* High 16 bits of cluster in FAT32 */
        __le16  time,date,start;/* time, date and first cluster */
        __le32  size;           /* file size (in bytes) */
};

This is the predefined structure for each directory entry. Once you reach the beginning of that cluster,freadthe size of the structure, and you can get all the parameters in the variables respectively.

Attributes

In the structure, we can locate 1 byte of data storing the attribute of the file. Actually this tells us a lot:

Bit	Mask	Description
0	0x01	Read-Only
1	0x02	Hidden
2	0x04	System Files
3	0x08	Volume Label
4	0x10	Subdirectory
5	0x20	Archive
6	0x40	Device
7	0x80	Reserved
8	0x0F	Long File Name (LFN)

In C programming, we can apply bitwise AND (&) to check a particular attribute, e.g.,

if((dir_entry.attr & 0x10) != 0) {
  /* It is a subdirectory */
 }