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@(#)dir.5 8.3 (Berkeley) 4/19/94
.Dd April 19, 1994 .Dt DIR 5 .Os BSD 4.2 .Sh NAME .Nm dir , .Nm dirent .Nd directory file format .Sh SYNOPSIS .Fd #include <sys/types.h> .Fd #include <sys/dir.h> .Sh DESCRIPTION Directories provide a convenient hierarchical method of grouping files while obscuring the underlying details of the storage medium. A directory file is differentiated from a plain file by a flag in its .Xr inode 5 entry. It consists of records (directory entries) each of which contains information about a file and a pointer to the file itself. Directory entries may contain other directories as well as plain files; such nested directories are refered to as subdirectories. A hierarchy of directories and files is formed in this manner and is called a file system (or referred to as a file system tree). An entry in this tree,
nested or not nested,
is a pathname.
p Each directory file contains two special directory entries; one is a pointer to the directory itself called dot .Ql . and the other a pointer to its parent directory called dot-dot .Ql .. . Dot and dot-dot are valid pathnames, however, the system root directory .Ql / , has no parent and dot-dot points to itself like dot.
p File system nodes are ordinary directory files on which has been grafted a file system object, such as a physical disk or a partitioned area of such a disk. (See .Xr mount 1 and .Xr mount 8 . )
p The directory entry format is defined in the file .Aq sys/dirent.h and further in the file .Aq dirent.h . When the macro .Dv _DARWIN_FEATURE_64_BIT_INODE is not defined (see .Xr stat 2 for more information on this macro), the .Fa dirent structure is defined as: d -literal /*** Excerpt from <sys/dirent.h> ***/ /* * The dirent structure defines the format of directory entries. * * A directory entry has a struct dirent at the front of it, containing its * inode number, the length of the entry, and the length of the name * contained in the entry. These are followed by the name padded to a 4 * byte boundary with null bytes. All names are guaranteed null terminated. * The maximum length of a name in a directory is 255. */ struct dirent { /* when _DARWIN_FEATURE_64_BIT_INODE is NOT defined */ ino_t d_ino; /* file number of entry */ __uint16_t d_reclen; /* length of this record */ __uint8_t d_type; /* file type, see below */ __uint8_t d_namlen; /* length of string in d_name */ char d_name[255 + 1]; /* name must be no longer than this */ }; .Ed
p However, when the macro .Dv _DARWIN_FEATURE_64_BIT_INODE is defined, the .Fa dirent structure is defined as: d -literal /* * The dirent structure defines the format of directory entries. * * A directory entry has a struct dirent at the front of it, containing its * inode number, the length of the entry, and the length of the name * contained in the entry. These are followed by the name padded to a 4 * byte boundary with null bytes. All names are guaranteed null terminated. * The maximum length of a name in a directory is 1023. */ struct dirent { /* when _DARWIN_FEATURE_64_BIT_INODE is defined */ ino_t d_fileno; /* file number of entry */ __uint16_t d_seekoff; /* seek offset (optional, used by servers) */ __uint16_t d_reclen; /* length of this record */ __uint16_t d_namlen; /* length of string in d_name */ __uint8_t d_type; /* file type, see below */ char d_name[1024]; /* name must be no longer than this */ }; .Ed
p In addition: d -literal /* * File types */ #define DT_UNKNOWN 0 #define DT_FIFO 1 #define DT_CHR 2 #define DT_DIR 4 #define DT_BLK 6 #define DT_REG 8 #define DT_LNK 10 #define DT_SOCK 12 #define DT_WHT 14 .Ed ----------------------------------------- d -literal /*** Excerpt from <dirent.h> ***/ #define d_fileno d_ino /* backward compatibility */ /* definitions for library routines operating on directories. */ #define DIRBLKSIZ 1024 struct _telldir; /* see telldir.h */ /* structure describing an open directory. */ typedef struct _dirdesc { int __dd_fd; /* file descriptor associated with directory */ long __dd_loc; /* offset in current buffer */ long __dd_size; /* amount of data returned by getdirentries */ char *__dd_buf; /* data buffer */ int __dd_len; /* size of data buffer */ long __dd_seek; /* magic cookie returned by getdirentries */ long __dd_rewind; /* magic cookie for rewinding */ int __dd_flags; /* flags for readdir */ pthread_mutex_t __dd_lock; /* for thread locking */ struct _telldir *__dd_td; /* telldir position recording */ } DIR; #define dirfd(dirp) ((dirp)->dd_fd) /* flags for opendir2 */ #define DTF_HIDEW 0x0001 /* hide whiteout entries */ #define DTF_NODUP 0x0002 /* don't return duplicate names */ #define DTF_REWIND 0x0004 /* rewind after reading union stack */ #define __DTF_READALL 0x0008 /* everything has been read */ .Ed .Sh SEE ALSO .Xr fs 5 , .Xr inode 5 .Sh HISTORY A .Nm file format appeared in .At v7 .