1.\" Copyright (c) 1983, 1991 Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)dir.5 6.2 (Berkeley) 4/29/91 33.\" 34.Dd April 29, 1991 35.Dt DIR 5 36.Os BSD 4.2 37.Sh NAME 38.Nm dir , 39.Nm dirent 40.Nd directory file format 41.Sh SYNOPSIS 42.Fd #include <sys/types.h> 43.Fd #include <sys/dir.h> 44.Sh DESCRIPTION 45Directories provide a convienent hierarchical method of grouping 46files while obscuring the underlying details of the storage medium. 47A directory file is differentiated from a plain file 48by a flag in its 49.Xr inode 5 50entry. 51It consists of records (directory entries) each of which contain 52information about a file and a pointer to the file itself. 53Directory entries may contain other directories 54as well as plain files; such nested directories are refered to as 55subdirectories. 56A hierarchy of directories and files is formed in this manner 57and is called a file system (or refered to as a file system tree). 58.\" An entry in this tree, 59.\" nested or not nested, 60.\" is a pathname. 61.Pp 62Each directory file contains two special directory entries; one is a pointer 63to the directory itself 64called dot 65.Ql \&. 66and the other a pointer to its parent directory called dot-dot 67.Ql \&.. . 68Dot and dot-dot 69are valid pathnames, however, 70the system root directory 71.Ql / , 72has no parent and dot-dot points to itself like dot. 73.Pp 74File system nodes are ordinary directory files on which has 75been grafted a file system object, such as a physical disk or a 76partitioned area of such a disk. 77(See 78.Xr mount 1 79and 80.Xr mount 8 . ) 81.Pp 82The directory entry format is defined in the file 83.Aq dirent.h : 84.Bd -literal 85#ifndef _DIRENT_H_ 86#define _DIRENT_H_ 87 88/* 89* A directory entry has a struct dirent at the front of it, containing its 90* inode number, the length of the entry, and the length of the name 91* contained in the entry. These are followed by the name padded to a 4 92* byte boundary with null bytes. All names are guaranteed null terminated. 93* The maximum length of a name in a directory is MAXNAMLEN. 94*/ 95 96struct dirent { 97 u_long d_fileno; /* file number of entry */ 98 u_short d_reclen; /* length of this record */ 99 u_short d_namlen; /* length of string in d_name */ 100#ifdef _POSIX_SOURCE 101 char d_name[MAXNAMLEN + 1]; /* maximum name length */ 102#else 103#define MAXNAMLEN 255 104 char d_name[MAXNAMLEN + 1]; /* maximum name length */ 105#endif 106 107}; 108 109#ifdef _POSIX_SOURCE 110typedef void * DIR; 111#else 112 113#define d_ino d_fileno /* backward compatibility */ 114 115/* definitions for library routines operating on directories. */ 116#define DIRBLKSIZ 1024 117 118/* structure describing an open directory. */ 119typedef struct _dirdesc { 120 int dd_fd; /* file descriptor associated with directory */ 121 long dd_loc; /* offset in current buffer */ 122 long dd_size; /* amount of data returned by getdirentries */ 123 char *dd_buf; /* data buffer */ 124 int dd_len; /* size of data buffer */ 125 long dd_seek; /* magic cookie returned by getdirentries */ 126} DIR; 127 128#define dirfd(dirp) ((dirp)->dd_fd) 129 130#ifndef NULL 131#define NULL 0 132#endif 133 134#endif /* _POSIX_SOURCE */ 135 136#ifndef KERNEL 137 138#include <sys/cdefs.h> 139 140#endif /* !KERNEL */ 141 142#endif /* !_DIRENT_H_ */ 143.Ed 144.Sh SEE ALSO 145.Xr fs 5 146.Xr inode 5 147.Sh HISTORY 148A 149.Nm 150file format appeared in 151.At v7 . 152