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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)dir.5 8.3 (Berkeley) 4/19/94 29.\" $FreeBSD$ 30.\" 31.Dd November 14, 2018 32.Dt DIR 5 33.Os 34.Sh NAME 35.Nm dir , 36.Nm dirent 37.Nd directory file format 38.Sh SYNOPSIS 39.In dirent.h 40.Sh DESCRIPTION 41Directories provide a convenient hierarchical method of grouping 42files while obscuring the underlying details of the storage medium. 43A directory file is differentiated from a plain file 44by a flag in its 45.Xr inode 5 46entry. 47It consists of records (directory entries) each of which contains 48information about a file and a pointer to the file itself. 49Directory entries may contain other directories 50as well as plain files; such nested directories are referred to as 51subdirectories. 52A hierarchy of directories and files is formed in this manner 53and is called a file system (or referred to as a file system tree). 54.\" An entry in this tree, 55.\" nested or not nested, 56.\" is a pathname. 57.Pp 58Each directory file contains two special directory entries; one is a pointer 59to the directory itself 60called dot 61.Ql .\& 62and the other a pointer to its parent directory called dot-dot 63.Ql \&.. . 64Dot and dot-dot 65are valid pathnames, however, 66the system root directory 67.Ql / , 68has no parent and dot-dot points to itself like dot. 69.Pp 70File system nodes are ordinary directory files on which has 71been grafted a file system object, such as a physical disk or a 72partitioned area of such a disk. 73(See 74.Xr mount 2 75and 76.Xr mount 8 . ) 77.Pp 78The directory entry format is defined in the file 79.In sys/dirent.h 80(which should not be included directly by applications): 81.Bd -literal 82#ifndef _SYS_DIRENT_H_ 83#define _SYS_DIRENT_H_ 84 85#include <machine/ansi.h> 86 87/* 88 * The dirent structure defines the format of directory entries returned by 89 * the getdirentries(2) system call. 90 * 91 * A directory entry has a struct dirent at the front of it, containing its 92 * inode number, the length of the entry, and the length of the name 93 * contained in the entry. These are followed by the name padded to a 8 94 * byte boundary with null bytes. All names are guaranteed null terminated. 95 * The maximum length of a name in a directory is MAXNAMLEN. 96 * Explicit pad is added between the last member of the header and 97 * d_name, to avoid having the ABI padding in the end of dirent on 98 * LP64 arches. There is code depending on d_name being last. Also, 99 * keeping this pad for ILP32 architectures simplifies compat32 layer. 100 */ 101 102struct dirent { 103 ino_t d_fileno; /* file number of entry */ 104 off_t d_off; /* directory offset of the next entry */ 105 __uint16_t d_reclen; /* length of this record */ 106 __uint8_t d_type; /* file type, see below */ 107 __uint8_t d_namlen; /* length of string in d_name */ 108 __uint32_t d_pad0; 109#if __BSD_VISIBLE 110#define MAXNAMLEN 255 111 char d_name[MAXNAMLEN + 1]; /* name must be no longer than this */ 112#else 113 char d_name[255 + 1]; /* name must be no longer than this */ 114#endif 115}; 116 117/* 118 * File types 119 */ 120#define DT_UNKNOWN 0 121#define DT_FIFO 1 122#define DT_CHR 2 123#define DT_DIR 4 124#define DT_BLK 6 125#define DT_REG 8 126#define DT_LNK 10 127#define DT_SOCK 12 128#define DT_WHT 14 129 130/* 131 * Convert between stat structure types and directory types. 132 */ 133#define IFTODT(mode) (((mode) & 0170000) >> 12) 134#define DTTOIF(dirtype) ((dirtype) << 12) 135 136/* 137 * The _GENERIC_DIRSIZ macro gives the minimum record length which will hold 138 * the directory entry. This returns the amount of space in struct direct 139 * without the d_name field, plus enough space for the name with a terminating 140 * null byte (dp->d_namlen+1), rounded up to a 8 byte boundary. 141 * 142 * XXX although this macro is in the implementation namespace, it requires 143 * a manifest constant that is not. 144 */ 145#define _GENERIC_DIRLEN(namlen) \ 146 ((__offsetof(struct dirent, d_name) + (namlen) + 1 + 7) & ~7) 147#define _GENERIC_DIRSIZ(dp) _GENERIC_DIRLEN((dp)->d_namlen) 148#endif /* __BSD_VISIBLE */ 149 150#ifdef _KERNEL 151#define GENERIC_DIRSIZ(dp) _GENERIC_DIRSIZ(dp) 152#endif 153 154#endif /* !_SYS_DIRENT_H_ */ 155.Ed 156.Sh SEE ALSO 157.Xr fs 5 , 158.Xr inode 5 159.Sh HISTORY 160A 161.Nm 162file format appeared in 163.At v7 . 164.Sh BUGS 165The usage of the member d_type of struct dirent is unportable as it is 166.Fx Ns -specific . 167It also may fail on certain file systems, for example the cd9660 file system. 168