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.\" $OpenBSD: dir.5,v 1.9 2003/06/02 23:30:14 millert Exp $
.\" $NetBSD: dir.5,v 1.5 1995/03/28 17:30:20 jtc Exp $
.\"
.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)dir.5 8.3 (Berkeley) 4/19/94
.\"
.Dd April 19, 1994
.Dt DIR 5
.Os
.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 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
.Pq Dq \&.
and the other a pointer to its parent directory called dot-dot
.Pq Dq \&.. .
Dot and dot-dot are valid pathnames, however, the system root directory
.Pq Dq / ,
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 8 ) .
.Pp
The directory entry format is defined in the file
.Aq Pa dirent.h :
.Bd -literal
#ifndef _DIRENT_H_
#define _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 null terminated.
* The maximum length of a name in a directory is MAXNAMLEN.
*/
struct dirent {
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 */
#ifdef _POSIX_SOURCE
char d_name[MAXNAMLEN + 1]; /* maximum name length */
#else
#define MAXNAMLEN 255
char d_name[MAXNAMLEN + 1]; /* maximum name length */
#endif
};
#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 */
} DIR;
#define dirfd(dirp) ((dirp)->dd_fd)
#ifndef NULL
#define NULL 0
#endif
#endif /* _POSIX_SOURCE */
#ifndef _KERNEL
#include <sys/cdefs.h>
#endif /* !_KERNEL */
#endif /* !_DIRENT_H_ */
.Ed
.Sh SEE ALSO
.Xr fs 5 ,
.Xr inode 5
.Sh HISTORY
A
.Nm dir
file format appeared in
.At v7 .
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