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32 .\" @(#)dir.5 8.3 (Berkeley) 4/19/94
41 .Nd directory file format
45 Directories provide a convenient hierarchical method of grouping
46 files while obscuring the underlying details of the storage medium.
47 A directory file is differentiated from a plain file
51 It consists of records (directory entries) each of which contains
52 information about a file and a pointer to the file itself.
53 Directory entries may contain other directories
54 as well as plain files; such nested directories are referred to as
56 A hierarchy of directories and files is formed in this manner
57 and is called a file system (or referred to as a file system tree).
58 .\" An entry in this tree,
59 .\" nested or not nested,
62 Each directory file contains two special directory entries; one is a pointer
63 to the directory itself
66 and the other a pointer to its parent directory called dot-dot
69 are valid pathnames, however,
70 the system root directory
72 has no parent and dot-dot points to itself like dot.
74 File system nodes are ordinary directory files on which has
75 been grafted a file system object, such as a physical disk or a
76 partitioned area of such a disk.
82 The directory entry format is defined in the file
84 (which should not be included directly by applications):
86 #ifndef _SYS_DIRENT_H_
87 #define _SYS_DIRENT_H_
89 #include <machine/ansi.h>
92 * The dirent structure defines the format of directory entries returned by
93 * the getdirentries(2) system call.
95 * A directory entry has a struct dirent at the front of it, containing its
96 * inode number, the length of the entry, and the length of the name
97 * contained in the entry. These are followed by the name padded to a 4
98 * byte boundary with null bytes. All names are guaranteed null terminated.
99 * The maximum length of a name in a directory is MAXNAMLEN.
103 __uint32_t d_fileno; /* file number of 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 */
108 char d_name[255 + 1]; /* name must be no longer than this */
110 #define MAXNAMLEN 255
111 char d_name[MAXNAMLEN + 1]; /* name must be no longer than this */
129 * Convert between stat structure types and directory types.
131 #define IFTODT(mode) (((mode) & 0170000) >> 12)
132 #define DTTOIF(dirtype) ((dirtype) << 12)
135 * The _GENERIC_DIRSIZ macro gives the minimum record length which will hold
136 * the directory entry. This requires the amount of space in struct direct
137 * without the d_name field, plus enough space for the name with a terminating
138 * null byte (dp->d_namlen+1), rounded up to a 4 byte boundary.
140 #define _GENERIC_DIRSIZ(dp) \
141 ((sizeof (struct dirent) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3))
144 #define GENERIC_DIRSIZ(dp) _GENERIC_DIRSIZ(dp)
147 #endif /* !_SYS_DIRENT_H_ */
155 file format appeared in
158 The usage of the member d_type of struct dirent is unportable as it is
160 It also may fail on certain file systems, for example the cd9660 file system.