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.\"     @(#)dir.5	8.3 (Berkeley) 4/19/94
.\" $FreeBSD: src/share/man/man5/dir.5,v 1.12.2.5 2001/12/17 11:30:13 ru Exp $
.\" $DragonFly: src/share/man/man5/dir.5,v 1.6 2006/02/17 19:37:10 swildner Exp $
.\"
.Dd March 5, 2005
.Dt DIR 5
.Os
.Sh NAME
.Nm dir ,
.Nm dirent
.Nd directory file format
.Sh SYNOPSIS
.In dirent.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 referred 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 2
and
.Xr mount 8 . )
.Pp
The directory entry format is defined in
.Aq Pa sys/dirent.h .
This file should not be included directly by applications.
.Sh SEE ALSO
.Xr fs 5 ,
.Xr inode 5
.Sh HISTORY
A
.Nm
file format appeared in
.At v7 .
.Sh BUGS
The usage of the member d_type of struct dirent is unportable as it is
.Dx Ns / Ns Fx Ns -specific .
It also may fail on certain filesystems, for example the cd9660 filesystem.