bsd/man/man5/dir.5

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  34 .\"     @(#)dir.5       8.3 (Berkeley) 4/19/94
  35 .\"
  36 .Dd April 19, 1994
  37 .Dt DIR 5
  38 .Os BSD 4.2
  39 .Sh NAME
  40 .Nm dir ,
  41 .Nm dirent
  42 .Nd directory file format
  43 .Sh SYNOPSIS
  44 .Fd #include <sys/types.h>
  45 .Fd #include <sys/dir.h>
  46 .Sh DESCRIPTION
  47 Directories provide a convenient hierarchical method of grouping
  48 files while obscuring the underlying details of the storage medium.
  49 A directory file is differentiated from a plain file
  50 by a flag in its
  51 .Xr inode 5
  52 entry.
  53 It consists of records (directory entries) each of which contains
  54 information about a file and a pointer to the file itself.
  55 Directory entries may contain other directories
  56 as well as plain files; such nested directories are refered to as
  57 subdirectories.
  58 A hierarchy of directories and files is formed in this manner
  59 and is called a file system (or referred to as a file system tree).
  60 .\" An entry in this tree,
  61 .\" nested or not nested,
  62 .\" is a pathname.
  63 .Pp
  64 Each directory file contains two special directory entries; one is a pointer
  65 to the directory itself
  66 called dot
  67 .Ql \&.
  68 and the other a pointer to its parent directory called dot-dot
  69 .Ql \&.. .
  70 Dot and dot-dot
  71 are valid pathnames, however,
  72 the system root directory
  73 .Ql / ,
  74 has no parent and dot-dot points to itself like dot.
  75 .Pp
  76 File system nodes are ordinary directory files on which has
  77 been grafted a file system object, such as a physical disk or a
  78 partitioned area of such a disk.
  79 (See
  80 .Xr mount 1
  81 and
  82 .Xr mount 8 . )
  83 .Pp
  84 The directory entry format is defined in the file
  85 .Aq dirent.h :
  86 .Bd -literal
  87 #ifndef _DIRENT_H_
  88 #define _DIRENT_H_
  89
  90 /*
  91 * A directory entry has a struct dirent at the front of it, containing its
  92 * inode number, the length of the entry, and the length of the name
  93 * contained in the entry.  These are followed by the name padded to a 4
  94 * byte boundary with null bytes.  All names are guaranteed null terminated.
  95 * The maximum length of a name in a directory is MAXNAMLEN.
  96 */
  97
  98 struct dirent {
  99         u_long  d_fileno;       /* file number of entry */
 100         u_short d_reclen;       /* length of this record */
 101         u_short d_namlen;       /* length of string in d_name */
 102 #ifdef _POSIX_SOURCE
 103         char    d_name[MAXNAMLEN + 1];  /* maximum name length */
 104 #else
 105 #define MAXNAMLEN       255
 106         char    d_name[MAXNAMLEN + 1];  /* maximum name length */
 107 #endif
 108
 109 };
 110
 111 #ifdef _POSIX_SOURCE
 112 typedef void *  DIR;
 113 #else
 114
 115 #define d_ino           d_fileno        /* backward compatibility */
 116
 117 /* definitions for library routines operating on directories. */
 118 #define DIRBLKSIZ       1024
 119
 120 /* structure describing an open directory. */
 121 typedef struct _dirdesc {
 122         int     dd_fd;    /* file descriptor associated with directory */
 123         long    dd_loc;   /* offset in current buffer */
 124         long    dd_size;  /* amount of data returned by getdirentries */
 125         char    *dd_buf;  /* data buffer */
 126         int     dd_len;   /* size of data buffer */
 127         long    dd_seek;  /* magic cookie returned by getdirentries */
 128 } DIR;
 129
 130 #define dirfd(dirp)     ((dirp)->dd_fd)
 131
 132 #ifndef NULL
 133 #define NULL    0
 134 #endif
 135
 136 #endif /* _POSIX_SOURCE */
 137
 138 #ifndef _KERNEL
 139
 140 #include <sys/cdefs.h>
 141
 142 #endif /* !_KERNEL */
 143
 144 #endif /* !_DIRENT_H_ */
 145 .Ed
 146 .Sh SEE ALSO
 147 .Xr fs 5 ,
 148 .Xr inode 5
 149 .Sh HISTORY
 150 A
 151 .Nm
 152 file format appeared in
 153 .At v7 .