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.\" 30.Dd November 14, 2018 31.Dt DIR 5 32.Os 33.Sh NAME 34.Nm dir , 35.Nm dirent 36.Nd directory file format 37.Sh SYNOPSIS 38.In dirent.h 39.Sh DESCRIPTION 40Directories provide a convenient hierarchical method of grouping 41files while obscuring the underlying details of the storage medium. 42A directory file is differentiated from a plain file 43by a flag in its 44.Xr inode 5 45entry. 46It consists of records (directory entries) each of which contains 47information about a file and a pointer to the file itself. 48Directory entries may contain other directories 49as well as plain files; such nested directories are referred to as 50subdirectories. 51A hierarchy of directories and files is formed in this manner 52and is called a file system (or referred to as a file system tree). 53.\" An entry in this tree, 54.\" nested or not nested, 55.\" is a pathname. 56.Pp 57Each directory file contains two special directory entries; one is a pointer 58to the directory itself 59called dot 60.Ql .\& 61and the other a pointer to its parent directory called dot-dot 62.Ql \&.. . 63Dot and dot-dot 64are valid pathnames, however, 65the system root directory 66.Ql / , 67has no parent and dot-dot points to itself like dot. 68.Pp 69File system nodes are ordinary directory files on which has 70been grafted a file system object, such as a physical disk or a 71partitioned area of such a disk. 72(See 73.Xr mount 2 74and 75.Xr mount 8 . ) 76.Pp 77The directory entry format is defined in the file 78.In sys/dirent.h 79(which should not be included directly by applications): 80.Bd -literal 81#ifndef _SYS_DIRENT_H_ 82#define _SYS_DIRENT_H_ 83 84#include <machine/ansi.h> 85 86/* 87 * The dirent structure defines the format of directory entries returned by 88 * the getdirentries(2) system call. 89 * 90 * A directory entry has a struct dirent at the front of it, containing its 91 * inode number, the length of the entry, and the length of the name 92 * contained in the entry. These are followed by the name padded to a 8 93 * byte boundary with null bytes. All names are guaranteed null terminated. 94 * The maximum length of a name in a directory is MAXNAMLEN. 95 * Explicit pad is added between the last member of the header and 96 * d_name, to avoid having the ABI padding in the end of dirent on 97 * LP64 arches. There is code depending on d_name being last. Also, 98 * keeping this pad for ILP32 architectures simplifies compat32 layer. 99 */ 100 101struct dirent { 102 ino_t d_fileno; /* file number of entry */ 103 off_t d_off; /* directory offset of the next 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 __uint32_t d_pad0; 108#if __BSD_VISIBLE 109#define MAXNAMLEN 255 110 char d_name[MAXNAMLEN + 1]; /* name must be no longer than this */ 111#else 112 char d_name[255 + 1]; /* name must be no longer than this */ 113#endif 114}; 115 116/* 117 * File types 118 */ 119#define DT_UNKNOWN 0 120#define DT_FIFO 1 121#define DT_CHR 2 122#define DT_DIR 4 123#define DT_BLK 6 124#define DT_REG 8 125#define DT_LNK 10 126#define DT_SOCK 12 127#define DT_WHT 14 128 129/* 130 * Convert between stat structure types and directory types. 131 */ 132#define IFTODT(mode) (((mode) & 0170000) >> 12) 133#define DTTOIF(dirtype) ((dirtype) << 12) 134 135/* 136 * The _GENERIC_DIRSIZ macro gives the minimum record length which will hold 137 * the directory entry. This returns the amount of space in struct direct 138 * without the d_name field, plus enough space for the name with a terminating 139 * null byte (dp->d_namlen+1), rounded up to a 8 byte boundary. 140 * 141 * XXX although this macro is in the implementation namespace, it requires 142 * a manifest constant that is not. 143 */ 144#define _GENERIC_DIRLEN(namlen) \ 145 ((__offsetof(struct dirent, d_name) + (namlen) + 1 + 7) & ~7) 146#define _GENERIC_DIRSIZ(dp) _GENERIC_DIRLEN((dp)->d_namlen) 147#endif /* __BSD_VISIBLE */ 148 149#ifdef _KERNEL 150#define GENERIC_DIRSIZ(dp) _GENERIC_DIRSIZ(dp) 151#endif 152 153#endif /* !_SYS_DIRENT_H_ */ 154.Ed 155.Sh SEE ALSO 156.Xr fs 5 , 157.Xr inode 5 158.Sh HISTORY 159A 160.Nm 161file format appeared in 162.At v7 . 163.Sh BUGS 164The usage of the member d_type of struct dirent is unportable as it is 165.Fx Ns -specific . 166It also may fail on certain file systems, for example the cd9660 file system. 167