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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 When the macro

89 .Dv _DARWIN_FEATURE_64_BIT_INODE

90 is not defined (see

91 .Xr stat 2

92 for more information on this macro), the

93 .Fa dirent

94 structure is defined as:

95 .Bd -literal

96 /*** Excerpt from <sys/dirent.h> ***/

97 /*

98 * The dirent structure defines the format of directory entries.

99 *

100 * A directory entry has a struct dirent at the front of it, containing its

101 * inode number, the length of the entry, and the length of the name

102 * contained in the entry. These are followed by the name padded to a 4

103 * byte boundary with null bytes. All names are guaranteed null terminated.

104 * The maximum length of a name in a directory is 255.

105 */

106

107 struct dirent { /* when _DARWIN_FEATURE_64_BIT_INODE is NOT defined */

108 ino_t d_ino; /* file number of entry */

109 __uint16_t d_reclen; /* length of this record */

110 __uint8_t d_type; /* file type, see below */

111 __uint8_t d_namlen; /* length of string in d_name */

112 char d_name[255 + 1]; /* name must be no longer than this */

113 };

114 .Ed

115 .Pp

116 However, when the macro

117 .Dv _DARWIN_FEATURE_64_BIT_INODE

118 is defined, the

119 .Fa dirent

120 structure is defined as:

121 .Bd -literal

122 /*

123 * The dirent structure defines the format of directory entries.

124 *

125 * A directory entry has a struct dirent at the front of it, containing its

126 * inode number, the length of the entry, and the length of the name

127 * contained in the entry. These are followed by the name padded to a 4

128 * byte boundary with null bytes. All names are guaranteed null terminated.

129 * The maximum length of a name in a directory is 1023.

130 */

131

132 struct dirent { /* when _DARWIN_FEATURE_64_BIT_INODE is defined */

133 ino_t d_fileno; /* file number of entry */

134 __uint64_t d_seekoff; /* seek offset (optional, used by servers) */

135 __uint16_t d_reclen; /* length of this record */

136 __uint16_t d_namlen; /* length of string in d_name */

137 __uint8_t d_type; /* file type, see below */

138 char d_name[1024]; /* name must be no longer than this */

139 };

140 .Ed

141 .Pp

142 In addition:

143 .Bd -literal

144 /*

145 * File types

146 */

147 #define DT_UNKNOWN 0

148 #define DT_FIFO 1

149 #define DT_CHR 2

150 #define DT_DIR 4

151 #define DT_BLK 6

152 #define DT_REG 8

153 #define DT_LNK 10

154 #define DT_SOCK 12

155 #define DT_WHT 14

156

157 .Ed

158 -----------------------------------------

159 .Bd -literal

160 /*** Excerpt from <dirent.h> ***/

161

162 #define d_fileno d_ino /* backward compatibility */

163

164 /* definitions for library routines operating on directories. */

165 #define DIRBLKSIZ 1024

166

167 struct _telldir; /* see telldir.h */

168

169 /* structure describing an open directory. */

170 typedef struct _dirdesc {

171 int __dd_fd; /* file descriptor associated with directory */

172 long __dd_loc; /* offset in current buffer */

173 long __dd_size; /* amount of data returned by getdirentries */

174 char *__dd_buf; /* data buffer */

175 int __dd_len; /* size of data buffer */

176 long __dd_seek; /* magic cookie returned by getdirentries */

177 long __dd_rewind; /* magic cookie for rewinding */

178 int __dd_flags; /* flags for readdir */

179 pthread_mutex_t __dd_lock; /* for thread locking */

180 struct _telldir *__dd_td; /* telldir position recording */

181 } DIR;

182

183 #define dirfd(dirp) ((dirp)->dd_fd)

184

185 /* flags for opendir2 */

186 #define DTF_HIDEW 0x0001 /* hide whiteout entries */

187 #define DTF_NODUP 0x0002 /* don't return duplicate names */

188 #define DTF_REWIND 0x0004 /* rewind after reading union stack */

189 #define __DTF_READALL 0x0008 /* everything has been read */

190 .Ed

191 .Sh SEE ALSO

192 .Xr fs 5 ,

193 .Xr inode 5

194 .Sh HISTORY

195 A

196 .Nm

197 file format appeared in

198 .At v7 .