DIR(5) BSD Programmer's Manual DIR(5)NAME
dirent - directory file format
SYNOPSIS
#include <sys/types.h>
#include <dirent.h>
DESCRIPTION
Directories provide a convenient hierarchical method of grouping files
while obscuring the underlying details of the storage medium. A directo-
ry file is differentiated from a plain file by a flag in its inode(5) en-
try. It consists of records (directory entries) each of which contains
information about a file and a pointer to the file itself. Directory en-
tries may contain other directories as well as plain files; such nested
directories are referred to as subdirectories. A hierarchy of directo-
ries and files is formed in this manner and is called a file system (or
referred to as a file system tree).
Each directory file contains two special directory entries; one is a
pointer to the directory itself called dot `.' and the other a pointer to
its parent directory called dot-dot `..'. Dot and dot-dot are valid path-
names, however, the system root directory `/', has no parent and dot-dot
points to itself like dot.
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 mount(8) for further information.
The dirent structure defines the format of directory entries returned by
the directory(3) C library routines and the getdirentries(2) system call.
A directory entry begins with a struct dirent, containing its inode num-
ber, the length of the entry, its type and the length of the name con-
tained in the entry. This is followed by the name padded to a 4 byte
boundary with nul bytes. All names are nul terminated. The maximum
length of a name in a directory is MAXNAMLEN.
The directory entry format is defined in the include file <dirent.h>:
struct dirent {
u_int32_t d_fileno; /* file number of entry */
u_int16_t d_reclen; /* length of this record */
u_int8_t d_type; /* file type, see below */
u_int8_t d_namlen; /* length of string in d_name */
#define MAXNAMLEN 255 /* name must be no longer than this */
char d_name[MAXNAMLEN + 1];
};
/*
* File types, found in the d_type field.
*/
#define DT_UNKNOWN 0
#define DT_FIFO 1 /* Fifo */
#define DT_CHR 2 /* Character device */
#define DT_DIR 4 /* Directory */
#define DT_BLK 6 /* Block device */
#define DT_REG 8 /* Regular file */
#define DT_LNK 10 /* Symbolic link */
#define DT_SOCK 12 /* Socket */
#define DT_WHT 14 /* Whiteout */
#define d_ino d_fileno /* backward compatibility */
SEE ALSOgetdirentries(2), directory(3), fs(5), inode(5)4.2 Berkeley Distribution May 3, 1995 2