DIR(5)                    OpenBSD Programmer's Manual                   DIR(5)

NAME
     dir, 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 point-
     er to its parent directory called dot-dot (``..'').  Dot and dot-dot are
     valid pathnames, however, the system root directory (``/''), has no par-
     ent 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)).

     The directory entry format is defined in the file <dirent.h>:

     /*
      * 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 NUL 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 */
     #define MAXNAMLEN       255
             char    d_name[MAXNAMLEN + 1];  /* maximum name length */
     };

     /*
      * 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

     /*
      * 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_NODUP       0x0002  /* don't return duplicate names */
     #define __DTF_READALL   0x0008  /* everything has been read */

     #endif /* _POSIX_SOURCE */

SEE ALSO
     getdirentries(2), fs(5), inode(5)

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

OpenBSD 4.7                      May 31, 2007                                2
