dirent(5) - NetBSD Manual Pages

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DIRENT(5)                 NetBSD File Formats Manual                 DIRENT(5)


NAME

     dirent -- directory format


SYNOPSIS

     #include <sys/types.h>
     #include <sys/dirent.h>


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 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 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(8).)

     The directory entry format is defined in the file <sys/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 an
      * 8 byte boundary with null bytes.  All names are guaranteed null
      * terminated.  The maximum length of a name in a directory is MAXNAMLEN.
      */

     struct dirent {
             ino_t     d_fileno;     /* file number of entry */
             uint16_t d_reclen;      /* length of this record */
             uint8_t  d_type;        /* file type, see below */
             uint8_t  d_namlen;      /* length of string in d_name */
     #define MAXNAMLEN       511
             char d_name[MAXNAMLEN + 1]; /* name must be no longer than this */
     };

     /*
      * 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


SEE ALSO

     getdents(2), fs(5), inode(5)


HISTORY

     A dir structure appeared in Version 7 AT&T UNIX.  The dirent structure
     appeared in NetBSD 1.3.

NetBSD 5.1.2                     June 22, 2007                    NetBSD 5.1.2