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<table class="head">
<tr>
<td class="head-ltitle">DIR(5)</td>
<td class="head-vol">File Formats Manual</td>
<td class="head-rtitle">DIR(5)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">dir</code>, <code class="Nm">dirent</code>
— <span class="Nd">directory file format</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="In">#include
<<a class="In">dirent.h</a>></code></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">Directories provide a convenient hierarchical method of grouping
files while obscuring the underlying details of the storage medium. A
directory file is differentiated from a plain file by a flag in its
<a class="Xr">inode(5)</a> 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 directories and files is formed in this manner and is called a
file system (or referred to as a file system tree).</p>
<p class="Pp">Each directory file contains two special directory entries; one is
a pointer to the directory itself called dot
‘<code class="Li">.</code>’ and the other a pointer to its
parent directory called dot-dot ‘<code class="Li">..</code>’.
Dot and dot-dot are valid pathnames, however, the system root directory
‘<code class="Li">/</code>’, has no parent and dot-dot points
to itself like dot.</p>
<p class="Pp">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 <a class="Xr">mount(2)</a> and
<a class="Xr">mount(8)</a>.)</p>
<p class="Pp">The directory entry format is defined in the file
<code class="In"><<a class="In">sys/dirent.h</a>></code> (which should
not be included directly by applications):</p>
<div class="Bd Pp Li">
<pre>#ifndef _SYS_DIRENT_H_
#define _SYS_DIRENT_H_
#include <machine/ansi.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 8
* byte boundary with null bytes. All names are guaranteed null terminated.
* The maximum length of a name in a directory is MAXNAMLEN.
* Explicit pad is added between the last member of the header and
* d_name, to avoid having the ABI padding in the end of dirent on
* LP64 arches. There is code depending on d_name being last. Also,
* keeping this pad for ILP32 architectures simplifies compat32 layer.
*/
struct dirent {
ino_t d_fileno; /* file number of entry */
off_t d_off; /* directory offset of the next 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 */
__uint32_t d_pad0;
#if __BSD_VISIBLE
#define MAXNAMLEN 255
char d_name[MAXNAMLEN + 1]; /* name must be no longer than this */
#else
char d_name[255 + 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
/*
* Convert between stat structure types and directory types.
*/
#define IFTODT(mode) (((mode) & 0170000) >> 12)
#define DTTOIF(dirtype) ((dirtype) << 12)
/*
* The _GENERIC_DIRSIZ macro gives the minimum record length which will hold
* the directory entry. This returns the amount of space in struct direct
* without the d_name field, plus enough space for the name with a terminating
* null byte (dp->d_namlen+1), rounded up to a 8 byte boundary.
*
* XXX although this macro is in the implementation namespace, it requires
* a manifest constant that is not.
*/
#define _GENERIC_DIRLEN(namlen) ((__offsetof(struct dirent, d_name) + (namlen) + 1 + 7) & ~7)
#define _GENERIC_DIRSIZ(dp) _GENERIC_DIRLEN((dp)->d_namlen)
#endif /* __BSD_VISIBLE */
#ifdef _KERNEL
#define GENERIC_DIRSIZ(dp) _GENERIC_DIRSIZ(dp)
#endif
#endif /* !_SYS_DIRENT_H_ */</pre>
</div>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">fs(5)</a>, <a class="Xr">inode(5)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">A <code class="Nm">dir</code> file format appeared in
<span class="Ux">Version 7 AT&T UNIX</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="BUGS"><a class="permalink" href="#BUGS">BUGS</a></h1>
<p class="Pp">The usage of the member d_type of struct dirent is unportable as
it is <span class="Ux">FreeBSD</span>-specific. It also may fail on certain
file systems, for example the cd9660 file system.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">November 14, 2018</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
