.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\" %sccs.include.redist.man%
.\" @(#)dir.5 8.2 (Berkeley) %G%
.Nd directory file format
.Fd #include <sys/types.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
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
A hierarchy of directories and files is formed in this manner
and is called a file system (or refered to as a file system tree).
.\" An entry in this tree,
.\" nested or not nested,
Each directory file contains two special directory entries; one is a pointer
and the other a pointer to its parent directory called dot-dot
are valid pathnames, however,
the system root directory
has no parent and dot-dot points to itself like dot.
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.
The directory entry format is defined in the file
* 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 MAXNAMLEN.
u_long d_fileno; /* file number of entry */
u_short d_reclen; /* length of this record */
u_short d_namlen; /* length of string in d_name */
char d_name[MAXNAMLEN + 1]; /* maximum name length */
char d_name[MAXNAMLEN + 1]; /* maximum name length */
#define d_ino d_fileno /* backward compatibility */
/* definitions for library routines operating on directories. */
/* 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 */
#define dirfd(dirp) ((dirp)->dd_fd)
#endif /* _POSIX_SOURCE */