bsd/man/man5/dir.5

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  34 .\"     @(#)dir.5       8.3 (Berkeley) 4/19/94
  35 .\"
  36 .Dd April 19, 1994
  37 .Dt DIR 5
  38 .Os BSD 4.2
  39 .Sh NAME
  40 .Nm dir ,
  41 .Nm dirent
  42 .Nd directory file format
  43 .Sh SYNOPSIS
  44 .Fd #include <sys/types.h>
  45 .Fd #include <sys/dir.h>
  46 .Sh DESCRIPTION
  47 Directories provide a convenient hierarchical method of grouping
  48 files while obscuring the underlying details of the storage medium.
  49 A directory file is differentiated from a plain file
  50 by a flag in its
  51 .Xr inode 5
  52 entry.
  53 It consists of records (directory entries) each of which contains
  54 information about a file and a pointer to the file itself.
  55 Directory entries may contain other directories
  56 as well as plain files; such nested directories are refered to as
  57 subdirectories.
  58 A hierarchy of directories and files is formed in this manner
  59 and is called a file system (or referred to as a file system tree).
  60 .\" An entry in this tree,
  61 .\" nested or not nested,
  62 .\" is a pathname.
  63 .Pp
  64 Each directory file contains two special directory entries; one is a pointer
  65 to the directory itself
  66 called dot
  67 .Ql \&.
  68 and the other a pointer to its parent directory called dot-dot
  69 .Ql \&.. .
  70 Dot and dot-dot
  71 are valid pathnames, however,
  72 the system root directory
  73 .Ql / ,
  74 has no parent and dot-dot points to itself like dot.
  75 .Pp
  76 File system nodes are ordinary directory files on which has
  77 been grafted a file system object, such as a physical disk or a
  78 partitioned area of such a disk.
  79 (See
  80 .Xr mount 1
  81 and
  82 .Xr mount 8 . )
  83 .Pp
  84 The directory entry format is defined in the file
  85 .Aq sys/dirent.h
  86 and further in the file
  87 .Aq dirent.h :
  88 .Bd -literal
  89 /*** Excerpt from <sys/dirent.h> ***/
  90 /*
  91  * The dirent structure defines the format of directory entries returned by
  92  * the getdirentries(2) system call.
  93  *
  94  * A directory entry has a struct dirent at the front of it, containing its
  95  * inode number, the length of the entry, and the length of the name
  96  * contained in the entry.  These are followed by the name padded to a 4
  97  * byte boundary with null bytes.  All names are guaranteed null terminated.
  98  * The maximum length of a name in a directory is MAXNAMLEN.
  99  * The dirent structure defines the format of directory entries returned by
 100  * the getdirentries(2) system call.
 101  */
 102
 103 #ifndef _SYS_DIRENT_H
 104 #define _SYS_DIRENT_H
 105
 106 struct dirent {
 107         u_int32_t d_fileno;             /* file number of entry */
 108         u_int16_t d_reclen;             /* length of this record */
 109         u_int8_t  d_type;               /* file type, see below */
 110         u_int8_t  d_namlen;             /* length of string in d_name */
 111 #ifdef _POSIX_SOURCE
 112         char    d_name[255 + 1];        /* name must be no longer than this */
 113 #else
 114 #define MAXNAMLEN       255
 115         char    d_name[MAXNAMLEN + 1];  /* name must be no longer than this */
 116 #endif
 117 };
 118
 119 /*
 120  * File types
 121  */
 122 #define DT_UNKNOWN       0
 123 #define DT_FIFO          1
 124 #define DT_CHR           2
 125 #define DT_DIR           4
 126 #define DT_BLK           6
 127 #define DT_REG           8
 128 #define DT_LNK          10
 129 #define DT_SOCK         12
 130 #define DT_WHT          14
 131
 132 #endif /* !_SYS_DIRENT_H_ */
 133
 134 .Ed
 135 -----------------------------------------
 136 .Bd -literal
 137 /*** Excerpt from <dirent.h> ***/
 138
 139 #ifndef _DIRENT_H
 140 #define _DIRENT_H
 141
 142 #ifdef _POSIX_SOURCE
 143 typedef void *  DIR;
 144 #else
 145
 146 #define d_ino           d_fileno        /* backward compatibility */
 147
 148 /* definitions for library routines operating on directories. */
 149 #define DIRBLKSIZ       1024
 150
 151 struct _telldir;                /* see telldir.h */
 152
 153 /* structure describing an open directory. */
 154 typedef struct _dirdesc {
 155         int     dd_fd;          /* file descriptor associated with directory */
 156         long    dd_loc;         /* offset in current buffer */
 157         long    dd_size;        /* amount of data returned by getdirentries */
 158         char    *dd_buf;        /* data buffer */
 159         int     dd_len;         /* size of data buffer */
 160         long    dd_seek;        /* magic cookie returned by getdirentries */
 161         long    dd_rewind;      /* magic cookie for rewinding */
 162         int     dd_flags;       /* flags for readdir */
 163         pthread_mutex_t dd_lock; /* for thread locking */
 164         struct _telldir *dd_td; /* telldir position recording */
 165 } DIR;
 166
 167 #define dirfd(dirp)     ((dirp)->dd_fd)
 168
 169 /* flags for opendir2 */
 170 #define DTF_HIDEW       0x0001  /* hide whiteout entries */
 171 #define DTF_NODUP       0x0002  /* don't return duplicate names */
 172 /* structure describing an open directory. */
 173 typedef struct _dirdesc {
 174         int     dd_fd;          /* file descriptor associated with directory */
 175         long    dd_loc;         /* offset in current buffer */
 176         long    dd_size;        /* amount of data returned by getdirentries */
 177         char    *dd_buf;        /* data buffer */
 178         int     dd_len;         /* size of data buffer */
 179         long    dd_seek;        /* magic cookie returned by getdirentries */
 180         long    dd_rewind;      /* magic cookie for rewinding */
 181         int     dd_flags;       /* flags for readdir */
 182         pthread_mutex_t dd_lock; /* for thread locking */
 183         struct _telldir *dd_td; /* telldir position recording */
 184 } DIR;
 185
 186 #define dirfd(dirp)     ((dirp)->dd_fd)
 187
 188 /* flags for opendir2 */
 189 #define DTF_HIDEW       0x0001  /* hide whiteout entries */
 190 #define DTF_NODUP       0x0002  /* don't return duplicate names */
 191 #define DTF_REWIND      0x0004  /* rewind after reading union stack */
 192 #define __DTF_READALL   0x0008  /* everything has been read */
 193
 194 #ifndef NULL
 195 #define NULL    0
 196 #endif
 197
 198 #endif /* _POSIX_SOURCE */
 199
 200 #endif /* !_DIRENT_H_ */
 201 .Ed
 202 .Sh SEE ALSO
 203 .Xr fs 5 ,
 204 .Xr inode 5
 205 .Sh HISTORY
 206 A
 207 .Nm
 208 file format appeared in
 209 .At v7 .