xref: /csrg-svn/share/man/man5/dir.5 (revision 69189)

.\" Copyright (c) 1983, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)dir.5	8.4 (Berkeley) 05/03/95
.\"
.Dd
.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.
.Pp
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.
.Pp
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 . )
.Pp
The directory entry format is defined in the file
.Aq dirent.h :
.Bd -literal
#ifndef _DIRENT_H_
#define _DIRENT_H_

/*
 * The dirent structure defines the format of directory entries returned by
 * the getdirentries(2) system call.
 *
 * 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 MAXNAMLEN.
 */

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 */
#ifdef _POSIX_SOURCE
	char	d_name[255 + 1];	/* name must be no longer than this */
#else
#define	MAXNAMLEN	255
	char	d_name[MAXNAMLEN + 1];	/* name must be no longer than this */
#endif
};

/*
 * 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

/*
 * Convert between stat structure types and directory types.
 */
#define	IFTODT(mode)	(((mode) & 0170000) >> 12)
#define	DTTOIF(dirtype)	((dirtype) << 12)

#ifdef _POSIX_SOURCE
typedef void *	DIR;
#else

#define	d_ino		d_fileno	/* backward compatibility */

/* definitions for library routines operating on directories. */
#define	DIRBLKSIZ	1024

/* 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 */
} 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 */

#ifndef NULL
#define	NULL	0
#endif

#endif /* _POSIX_SOURCE */

#ifndef KERNEL

#include <sys/cdefs.h>

__BEGIN_DECLS
DIR *opendir __P((const char *));
struct dirent *readdir __P((DIR *));
void rewinddir __P((DIR *));
int closedir __P((DIR *));
#ifndef _POSIX_SOURCE
DIR *__opendir2 __P((const char *, int));
long telldir __P((const DIR *));
void seekdir __P((DIR *, long));
int scandir __P((const char *, struct dirent ***,
    int (*)(struct dirent *), int (*)(const void *, const void *)));
int alphasort __P((const void *, const void *));
int getdirentries __P((int, char *, int, long *));
#endif /* not POSIX */
__END_DECLS

#endif /* !KERNEL */

#endif /* !_DIRENT_H_ */
.Ed
.Sh SEE ALSO
.Xr fs 5
.Xr inode 5
.Sh HISTORY
A
.Nm
file format appeared in
.At v7 .