usr/sys/inode.h

/*
 * The I node is the focus of all
 * file activity in unix. There is a unique
 * inode allocated for each active file,
 * each current directory, each mounted-on
 * file, text file, and the root. An inode is 'named'
 * by its dev/inumber pair. (iget/iget.c)
 * Data, from mode on, is read in
 * from permanent inode on volume.
 */
struct  inode
{
        char    i_flag;
        char    i_count;        /* reference count */
        int     i_dev;          /* device where inode resides */
        int     i_number;       /* i number, 1-to-1 with device address */
        int     i_mode;
        char    i_nlink;        /* directory entries */
        char    i_uid;          /* owner */
        char    i_gid;          /* group of owner */
        char    i_size0;        /* most significant of size */
        char    *i_size1;       /* least sig */
        int     i_addr[8];      /* device addresses constituting file */
        int     i_lastr;        /* last logical block read (for read-ahead) */
} inode[NINODE];

/* flags */
#define ILOCK   01              /* inode is locked */
#define IUPD    02              /* inode has been modified */
#define IACC    04              /* inode access time to be updated */
#define IMOUNT  010             /* inode is mounted on */
#define IWANT   020             /* some process waiting on lock */
#define ITEXT   040             /* inode is pure text prototype */

/* modes */
#define IALLOC  0100000         /* file is used */
#define IFMT    060000          /* type of file */
#define         IFDIR   040000  /* directory */
#define         IFCHR   020000  /* character special */
#define         IFBLK   060000  /* block special, 0 is regular */
#define ILARG   010000          /* large addressing algorithm */
#define ISUID   04000           /* set user id on execution */
#define ISGID   02000           /* set group id on execution */
#define ISVTX   01000           /* save swapped text even after use */
#define IREAD   0400            /* read, write, execute permissions */
#define IWRITE  0200
#define IEXEC   0100