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 sys/dirent.h
  86 and further in the file
  87 .Aq dirent.h .
  88 When the macro
  89 .Dv _DARWIN_FEATURE_64_BIT_INODE
  90 is not defined (the
  91 .Ft ino_t
  92 type is 32-bits), the
  93 .Fa dirent
  94 structure is defined as:
  95 .Bd -literal
  96 /*** Excerpt from <sys/dirent.h> ***/
  97 /*
  98  * The dirent structure defines the format of directory entries.
  99  *
 100  * A directory entry has a struct dirent at the front of it, containing its
 101  * inode number, the length of the entry, and the length of the name
 102  * contained in the entry.  These are followed by the name padded to a 4
 103  * byte boundary with null bytes.  All names are guaranteed null terminated.
 104  * The maximum length of a name in a directory is 255.
 105  */
 106
 107 struct dirent { /* when _DARWIN_FEATURE_64_BIT_INODE is NOT defined */
 108         ino_t      d_ino;                /* file number of entry */
 109         __uint16_t d_reclen;             /* length of this record */
 110         __uint8_t  d_type;               /* file type, see below */
 111         __uint8_t  d_namlen;             /* length of string in d_name */
 112         char    d_name[255 + 1];   /* name must be no longer than this */
 113 };
 114 .Ed
 115 .Pp
 116 However, when the macro
 117 .Dv _DARWIN_FEATURE_64_BIT_INODE
 118 is defined, the
 119 .Ft ino_t
 120 type will be 64-bits (force 64-bit inode mode by defining the
 121 .Dv _DARWIN_USE_64_BIT_INODE
 122 macro before including header files).
 123 This will cause symbol variants of the directory routines, with the
 124 .Fa $INODE64
 125 suffixes, to be automatically linked in.
 126 In addition, the
 127 .Fa dirent
 128 structure will now be defined as:
 129 .Bd -literal
 130 /*
 131  * The dirent structure defines the format of directory entries.
 132  *
 133  * A directory entry has a struct dirent at the front of it, containing its
 134  * inode number, the length of the entry, and the length of the name
 135  * contained in the entry.  These are followed by the name padded to a 4
 136  * byte boundary with null bytes.  All names are guaranteed null terminated.
 137  * The maximum length of a name in a directory is 1023.
 138  */
 139
 140 struct dirent { /* when _DARWIN_FEATURE_64_BIT_INODE is defined */
 141         ino_t      d_fileno;     /* file number of entry */
 142         __uint16_t d_seekoff;    /* seek offset (optional, used by servers) */
 143         __uint16_t d_reclen;     /* length of this record */
 144         __uint16_t d_namlen;     /* length of string in d_name */
 145         __uint8_t  d_type;       /* file type, see below */
 146         char    d_name[1024];    /* name must be no longer than this */
 147 };
 148 .Ed
 149 .Pp
 150 In addition:
 151 .Bd -literal
 152 /*
 153  * File types
 154  */
 155 #define DT_UNKNOWN       0
 156 #define DT_FIFO          1
 157 #define DT_CHR           2
 158 #define DT_DIR           4
 159 #define DT_BLK           6
 160 #define DT_REG           8
 161 #define DT_LNK          10
 162 #define DT_SOCK         12
 163 #define DT_WHT          14
 164
 165 .Ed
 166 -----------------------------------------
 167 .Bd -literal
 168 /*** Excerpt from <dirent.h> ***/
 169
 170 #define d_fileno        d_ino        /* backward compatibility */
 171
 172 /* definitions for library routines operating on directories. */
 173 #define DIRBLKSIZ       1024
 174
 175 struct _telldir;                /* see telldir.h */
 176
 177 /* structure describing an open directory. */
 178 typedef struct _dirdesc {
 179         int     __dd_fd;      /* file descriptor associated with directory */
 180         long    __dd_loc;     /* offset in current buffer */
 181         long    __dd_size;    /* amount of data returned by getdirentries */
 182         char    *__dd_buf;    /* data buffer */
 183         int     __dd_len;     /* size of data buffer */
 184         long    __dd_seek;    /* magic cookie returned by getdirentries */
 185         long    __dd_rewind;  /* magic cookie for rewinding */
 186         int     __dd_flags;   /* flags for readdir */
 187         pthread_mutex_t __dd_lock; /* for thread locking */
 188         struct _telldir *__dd_td; /* telldir position recording */
 189 } DIR;
 190
 191 #define dirfd(dirp)     ((dirp)->dd_fd)
 192
 193 /* flags for opendir2 */
 194 #define DTF_HIDEW       0x0001  /* hide whiteout entries */
 195 #define DTF_NODUP       0x0002  /* don't return duplicate names */
 196 #define DTF_REWIND      0x0004  /* rewind after reading union stack */
 197 #define __DTF_READALL   0x0008  /* everything has been read */
 198 .Ed
 199 .Sh SEE ALSO
 200 .Xr fs 5 ,
 201 .Xr inode 5
 202 .Sh HISTORY
 203 A
 204 .Nm
 205 file format appeared in
 206 .At v7 .