1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. 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 8.3 (Berkeley) 4/19/94 33.\" $FreeBSD$ 34.\" 35.Dd April 19, 1994 36.Dt DIR 5 37.Os 38.Sh NAME 39.Nm dir , 40.Nm dirent 41.Nd directory file format 42.Sh SYNOPSIS 43.In dirent.h 44.Sh DESCRIPTION 45Directories provide a convenient 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 contains 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 referred to as 55subdirectories. 56A hierarchy of directories and files is formed in this manner 57and is called a file system (or referred 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 2 79and 80.Xr mount 8 . ) 81.Pp 82The directory entry format is defined in the file 83.In sys/dirent.h 84(which should not be included directly by applications): 85.Bd -literal 86#ifndef _SYS_DIRENT_H_ 87#define _SYS_DIRENT_H_ 88 89#include <machine/ansi.h> 90 91/* 92 * The dirent structure defines the format of directory entries returned by 93 * the getdirentries(2) system call. 94 * 95 * A directory entry has a struct dirent at the front of it, containing its 96 * inode number, the length of the entry, and the length of the name 97 * contained in the entry. These are followed by the name padded to a 4 98 * byte boundary with null bytes. All names are guaranteed null terminated. 99 * The maximum length of a name in a directory is MAXNAMLEN. 100 */ 101 102struct dirent { 103 __uint32_t d_fileno; /* file number of entry */ 104 __uint16_t d_reclen; /* length of this record */ 105 __uint8_t d_type; /* file type, see below */ 106 __uint8_t d_namlen; /* length of string in d_name */ 107#ifdef _POSIX_SOURCE 108 char d_name[255 + 1]; /* name must be no longer than this */ 109#else 110#define MAXNAMLEN 255 111 char d_name[MAXNAMLEN + 1]; /* name must be no longer than this */ 112#endif 113}; 114 115/* 116 * File types 117 */ 118#define DT_UNKNOWN 0 119#define DT_FIFO 1 120#define DT_CHR 2 121#define DT_DIR 4 122#define DT_BLK 6 123#define DT_REG 8 124#define DT_LNK 10 125#define DT_SOCK 12 126#define DT_WHT 14 127 128/* 129 * Convert between stat structure types and directory types. 130 */ 131#define IFTODT(mode) (((mode) & 0170000) >> 12) 132#define DTTOIF(dirtype) ((dirtype) << 12) 133 134/* 135 * The _GENERIC_DIRSIZ macro gives the minimum record length which will hold 136 * the directory entry. This requires the amount of space in struct direct 137 * without the d_name field, plus enough space for the name with a terminating 138 * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary. 139 */ 140#define _GENERIC_DIRSIZ(dp) \ 141 ((sizeof (struct dirent) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3)) 142 143#ifdef _KERNEL 144#define GENERIC_DIRSIZ(dp) _GENERIC_DIRSIZ(dp) 145#endif 146 147#endif /* !_SYS_DIRENT_H_ */ 148.Ed 149.Sh SEE ALSO 150.Xr fs 5 , 151.Xr inode 5 152.Sh HISTORY 153A 154.Nm 155file format appeared in 156.At v7 . 157.Sh BUGS 158The usage of the member d_type of struct dirent is unportable as it is 159.Fx Ns -specific . 160It also may fail on certain file systems, for example the cd9660 file system. 161