DIR(5) File Formats Manual DIR(5)
dir - format of directories
A directory behaves exactly like an ordinary file, save that no user
may write into a directory. The fact that a file is a directory is
indicated by a bit in the flag word of its i-node entry see, filsys(5).
The structure of a directory entry as given in the include file is:
/* Copyright (C) 1991, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
#endif /* sys/dir.h */
By convention, the first two entries in each directory are for `.' and
`..'. The first is an entry for the directory itself. The second is
for the parent directory. The meaning of `..' is modified for the root
directory of the master file system and for the root directories of
removable file systems. In the first case, there is no parent, and in
the second, the system does not permit off-device references. There‐
fore in both cases `..' has the same meaning as `.'.