1.\" $OpenBSD: dir.5,v 1.10 2003/07/04 23:06:01 millert Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)dir.5 8.4 (Berkeley) 5/3/95 31.\" 32.Dd May 3, 1995 33.Dt DIR 5 34.Os 35.Sh NAME 36.Nm dir , 37.Nm dirent 38.Nd directory file format 39.Sh SYNOPSIS 40.Fd #include <sys/types.h> 41.Fd #include <dirent.h> 42.Sh DESCRIPTION 43Directories provide a convenient hierarchical method of grouping 44files while obscuring the underlying details of the storage medium. 45A directory file is differentiated from a plain file by a flag in its 46.Xr inode 5 47entry. 48It consists of records (directory entries) each of which contains 49information about a file and a pointer to the file itself. 50Directory entries may contain other directories as well as plain files; 51such nested directories are referred to as subdirectories. 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 called dot 60.Pq Dq \&. 61and the other a pointer to its parent directory called dot-dot 62.Pq Dq \&.. . 63Dot and dot-dot are valid pathnames, however, the system root directory 64.Pq Dq / , 65has no parent and dot-dot points to itself like dot. 66.Pp 67File system nodes are ordinary directory files on which has 68been grafted a file system object, such as a physical disk or a 69partitioned area of such a disk (see 70.Xr mount 8 ) . 71.Pp 72The directory entry format is defined in the file 73.Aq Pa dirent.h : 74.Bd -literal 75/* 76 * A directory entry has a struct dirent at the front of it, containing 77 * its inode number, the length of the entry, and the length of the name 78 * contained in the entry. These are followed by the name padded to a 4 79 * byte boundary with null bytes. All names are guaranteed NUL terminated. 80 * The maximum length of a name in a directory is MAXNAMLEN. 81 */ 82 83struct dirent { 84 u_int32_t d_fileno; /* file number of entry */ 85 u_int16_t d_reclen; /* length of this record */ 86 u_int8_t d_type; /* file type, see below */ 87 u_int8_t d_namlen; /* length of string in d_name */ 88#define MAXNAMLEN 255 89 char d_name[MAXNAMLEN + 1]; /* maximum name length */ 90}; 91 92/* 93 * File types 94 */ 95#define DT_UNKNOWN 0 96#define DT_FIFO 1 97#define DT_CHR 2 98#define DT_DIR 4 99#define DT_BLK 6 100#define DT_REG 8 101#define DT_LNK 10 102#define DT_SOCK 12 103#define DT_WHT 14 104 105/* 106 * Convert between stat structure types and directory types. 107 */ 108#define IFTODT(mode) (((mode) & 0170000) >> 12) 109#define DTTOIF(dirtype) ((dirtype) << 12) 110 111#ifdef _POSIX_SOURCE 112typedef void * DIR; 113#else 114 115#define d_ino d_fileno /* backward compatibility */ 116 117/* definitions for library routines operating on directories. */ 118#define DIRBLKSIZ 1024 119 120/* structure describing an open directory. */ 121typedef struct _dirdesc { 122 int dd_fd; /* file descriptor associated with directory */ 123 long dd_loc; /* offset in current buffer */ 124 long dd_size; /* amount of data returned by getdirentries */ 125 char *dd_buf; /* data buffer */ 126 int dd_len; /* size of data buffer */ 127 long dd_seek; /* magic cookie returned by getdirentries */ 128 long dd_rewind; /* magic cookie for rewinding */ 129 int dd_flags; /* flags for readdir */ 130} DIR; 131 132#define dirfd(dirp) ((dirp)->dd_fd) 133 134/* flags for opendir2 */ 135#define DTF_HIDEW 0x0001 /* hide whiteout entries */ 136#define DTF_NODUP 0x0002 /* don't return duplicate names */ 137#define DTF_REWIND 0x0004 /* rewind after reading union stack */ 138#define __DTF_READALL 0x0008 /* everything has been read */ 139 140#endif /* _POSIX_SOURCE */ 141.Ed 142.Sh SEE ALSO 143.Xr getdirentries 2 , 144.Xr fs 5 , 145.Xr inode 5 146.Sh HISTORY 147A 148.Nm dir 149file format appeared in 150.At v7 . 151