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DIR(5)                      BSD File Formats Manual                     DIR(5)

NAME
     dir, dirent -- directory file format

SYNOPSIS
     #include <&lt;sys/types.h>&gt;
     #include <&lt;sys/dir.h>&gt;

DESCRIPTION
     Directories provide a convenient hierarchical method of grouping files
     while obscuring the underlying details of the storage medium.  A direc-
     tory file is differentiated from a plain file by a flag in its 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).

     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
     pathnames, 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(1) and mount(8).)

     The directory entry format is defined in the file <sys/dirent.h> and fur-
     ther in the file <dirent.h>:

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

     #ifndef _SYS_DIRENT_H
     #define _SYS_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 */
     #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

     #endif /* !_SYS_DIRENT_H_ */

     -----------------------------------------

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

     #ifndef _DIRENT_H
     #define _DIRENT_H

     #ifdef _POSIX_SOURCE
     typedef void *  DIR;
     #else

     #define d_ino           d_fileno        /* 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 */
     /* 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 */

     #ifndef NULL
     #define NULL    0
     #endif

     #endif /* _POSIX_SOURCE */

     #endif /* !_DIRENT_H_ */

SEE ALSO
     fs(5), inode(5)

HISTORY
     A dir file format appeared in Version 7 AT&T UNIX.

4.2 Berkeley Distribution       April 19, 1994       4.2 Berkeley Distribution