DIR(5) BSD Reference Manual DIR(5)
dir, dirent - directory file format
#include <sys/types.h>
#include <dirent.h>
Directories provide a convenient hierarchical method of grouping files
while obscuring the underlying details of the storage medium. A directory
file is differentiated from a plain file by a flag in its inode(5) entry.
It consists of records (directory entries) each of which contains infor-
mation about a file and a pointer to the file itself. Directory entries
may contain other directories as well as plain files; such nested direc-
tories are referred to as subdirectories. A hierarchy of directories and
files is formed in this manner and is called a filesystem (or referred to
as a filesystem tree).
Each directory file contains two special directory entries; one is a
pointer to the directory itself called dot (".") and the other a pointer
to its parent directory called dot-dot (".."). Dot and dot-dot are valid
pathnames, however, the system root directory ("/"), has no parent and
dot-dot points to itself like dot.
Filesystem nodes are ordinary directory files on which has been grafted a
filesystem object, such as a physical disk or a partitioned area of such
a disk (see mount(8)).
The directory entry format is defined in the file <dirent.h>:
/*
* A directory entry has a struct dirent at the front of it, containing
* its inode number, the length of the entry, and the length of the name
* contained in the entry. These are followed by the name padded to a 4
* byte boundary with null bytes. All names are guaranteed NUL terminated.
* The maximum length of a name in a directory is MAXNAMLEN.
*/
struct dirent {
u_int32_t d_fileno; /* file number of entry */
u_int16_t d_reclen; /* length of this record */
u_int8_t d_type; /* file type, see below */
u_int8_t d_namlen; /* length of string in d_name */
#define MAXNAMLEN 255
char d_name[MAXNAMLEN + 1]; /* maximum name length */
};
/*
* File types
*/
#define DT_UNKNOWN 0
#define DT_FIFO 1
#define DT_CHR 2
#define DT_DIR 4
#define DT_BLK 6
#define DT_REG 8
#define DT_LNK 10
#define DT_SOCK 12
/*
* Convert between stat structure types and directory types.
*/
#define IFTODT(mode) (((mode) & 0170000) >> 12)
#define DTTOIF(dirtype) ((dirtype) << 12)
#ifdef _POSIX_SOURCE
typedef void * DIR;
#else
#define d_ino d_fileno /* backward compatibility */
/* definitions for library routines operating on directories. */
#define DIRBLKSIZ 1024
/* structure describing an open directory. */
typedef struct _dirdesc {
int dd_fd; /* file descriptor associated with directory */
long dd_loc; /* offset in current buffer */
long dd_size; /* amount of data returned by getdirentries */
char *dd_buf; /* data buffer */
int dd_len; /* size of data buffer */
long dd_seek; /* magic cookie returned by getdirentries */
long dd_rewind; /* magic cookie for rewinding */
int dd_flags; /* flags for readdir */
} DIR;
#define dirfd(dirp) ((dirp)->dd_fd)
/* flags for opendir2 */
#define DTF_NODUP 0x0002 /* don't return duplicate names */
#define __DTF_READALL 0x0008 /* everything has been read */
#endif /* _POSIX_SOURCE */
getdirentries(2), fs(5), inode(5)
A dir file format appeared in Version 7 AT&T UNIX.
MirBSD #10-current May 3, 1995 1