.\" $NetBSD: dir.5,v 1.5 1995/03/28 17:30:20 jtc Exp $
.\"
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.\" @(#)dir.5 8.3 (Berkeley) 4/19/94
.\"
.Dd April 19, 1994
.Dt DIR 5
.Os BSD 4.2
.Sh NAME
.Nm dir ,
.Nm dirent
.Nd directory file format
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/dir.h>
.Sh DESCRIPTION
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
.Xr inode 5
entry.
It consists of records (directory entries) each of which contains
information about a file and a pointer to the file itself.
Directory entries may contain other directories
as well as plain files; such nested directories are refered to as
subdirectories.
A hierarchy of directories and files is formed in this manner
and is called a file system (or referred to as a file system tree).
.\" An entry in this tree,
.\" nested or not nested,
.\" is a pathname.
.Pp
Each directory file contains two special directory entries; one is a pointer
to the directory itself
called dot
.Ql \&.
and the other a pointer to its parent directory called dot-dot
.Ql \&.. .
Dot and dot-dot
are valid pathnames, however,
the system root directory
.Ql / ,
has no parent and dot-dot points to itself like dot.
.Pp
File system nodes are ordinary directory files on which has
been grafted a file system object, such as a physical disk or a
partitioned area of such a disk.
(See
.Xr mount 1
and
.Xr mount 8 . )
.Pp
The directory entry format is defined in the file
.Aq sys/dirent.h
and further in the file
.Aq dirent.h .
When the macro
.Dv _DARWIN_FEATURE_64_BIT_INODE
is not defined (see
.Xr stat 2
for more information on this macro), the
.Fa dirent
structure is defined as:
.Bd -literal
/*** Excerpt from <sys/dirent.h> ***/
/*
* The dirent structure defines the format of directory entries.
*
* 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 null terminated.
* The maximum length of a name in a directory is 255.
*/
struct dirent { /* when _DARWIN_FEATURE_64_BIT_INODE is NOT defined */
ino_t d_ino; /* file number of entry */
__uint16_t d_reclen; /* length of this record */
__uint8_t d_type; /* file type, see below */
__uint8_t d_namlen; /* length of string in d_name */
char d_name[255 + 1]; /* name must be no longer than this */
};
.Ed
.Pp
However, when the macro
.Dv _DARWIN_FEATURE_64_BIT_INODE
is defined, the
.Fa dirent
structure is defined as:
.Bd -literal
/*
* The dirent structure defines the format of directory entries.
*
* 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 null terminated.
* The maximum length of a name in a directory is 1023.
*/
struct dirent { /* when _DARWIN_FEATURE_64_BIT_INODE is defined */
ino_t d_fileno; /* file number of entry */
__uint16_t d_seekoff; /* seek offset (optional, used by servers) */
__uint16_t d_reclen; /* length of this record */
__uint16_t d_namlen; /* length of string in d_name */
__uint8_t d_type; /* file type, see below */
char d_name[1024]; /* name must be no longer than this */
};
.Ed
.Pp
In addition:
.Bd -literal
/*
* 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
#define DT_WHT 14
.Ed
-----------------------------------------
.Bd -literal
/*** Excerpt from <dirent.h> ***/
#define d_fileno d_ino /* backward compatibility */
/* definitions for library routines operating on directories. */
#define DIRBLKSIZ 1024
struct _telldir; /* see telldir.h */
/* 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 */
pthread_mutex_t __dd_lock; /* for thread locking */
struct _telldir *__dd_td; /* telldir position recording */
} DIR;
#define dirfd(dirp) ((dirp)->dd_fd)
/* flags for opendir2 */
#define DTF_HIDEW 0x0001 /* hide whiteout entries */
#define DTF_NODUP 0x0002 /* don't return duplicate names */
#define DTF_REWIND 0x0004 /* rewind after reading union stack */
#define __DTF_READALL 0x0008 /* everything has been read */
.Ed
.Sh SEE ALSO
.Xr fs 5 ,
.Xr inode 5
.Sh HISTORY
A
.Nm
file format appeared in
.At v7 .