Data structure for a directory entry
Synopsis:
#include <dirent.h>
struct dirent {
#if __OFF_BITS__ == 64
ino_t d_ino;
off_t d_offset;
#elif __OFF_BITS__ == 32
# if defined(__LITTLEENDIAN__)
ino_t d_ino;
ino_t d_ino_hi;
off_t d_offset;
off_t d_offset_hi;
# elif defined(__BIGENDIAN__)
ino_t d_ino_hi;
ino_t d_ino;
off_t d_offset_hi;
off_t d_offset;
# else
# error endian not configured for system
# endif
#else
# error __OFF_BITS__ value is unsupported
#endif
int16_t d_reclen;
int16_t d_namelen;
char d_name[1]);
};
#ifdef __EXT_LF64SRC
struct dirent64 {
ino64_t d_ino;
off64_t d_offset;
int16_t d_reclen;
int16_t d_namelen;
char d_name[1]);
};
#endif
Description:
The dirent structure describes an entry in a directory.
The dirent64 structure is for large-file support.
Note: The large-file support functions and data types appear in the name space only if you define
_LARGEFILE64_SOURCE when you compile your code. For more information, see
Classification in What's in a Function
Description?
The members include:
- d_ino
- A mountpoint-unique file serial number. This serial number is often used in
various disk-checking utilities for such operations as
determining infinite-loop directory links. (Note that the
inode value cannot be zero, which would indicate that the
inode represents an unused entry.)
- d_offset
- In some filesystems, this member identifies the directory entry itself;
in others, it's the offset of the next directory entry.
For a disk-based filesystem, this value might be the actual
offset into the on-disk directory structure.
- d_reclen
- The size of this directory entry including the name and any other associated information
(such as an optional struct stat structure
appended to the struct dirent entry).
- d_namelen
- The length of the name not including the \0 string terminator. The terminator
must be present, but isn't counted.
- d_name
- The actual name of that directory entry.
Note: These structures provide d_name as a place-holder for the start of the
name, but do not supply storage for more than the leading bytes in the name.
If using
readdir(), the dirent structures returned by this function supply
enough space to hold the entire name.
If using
readdir_r(), you must
supply an appropriate buffer for the
dirent including name. This buffer size (in
bytes) is always large enough:
offsetof(struct dirent, d_name) + PATH_MAX
If handling
readdir() requests in a resource manager, you must generate
appropriate variable-length entries to return to the client. See
Returning directory
entries from _IO_READ in
Writing a Resource Manager.