Open System Services System Calls Reference Manual (G06.25+, H06.03+)

Files dir(4)
NAME
dir - Describes the format of directories
SYNOPSIS
#include <sys/types.h>
#include <dirent.h>
DESCRIPTION
A directory is a file that contains directory entries. The fact that a file is a directory is indicated
by a bit in the flag word of the inode entry for the file.
Users cannot write a directory. Users can read directory entries by making calls to the readdir()
function after opening the directory file by calling the opendir( ) function.
Directory entries are returned in directory entry structures, which are of variable length. Each
directory entry has a dirent structure at the beginning, containing its inode number, the length of
the entry, and the length of the filename contained in the entry. These structure components are
followed by the filename, padded to a 4-byte boundary with null bytes. All names are guaranteed
null-terminated. The maximum permitted length of a name in a directory can be obtained by cal-
ling the pathconf() function.
By convention, the first two entries in each directory are for . (dot) and ..(dot-dot). The . (dot)
entry is for the directory itself. The ..(dot-dot) entry is for the parent directory. The meaning of
..(dot-dot) is modified for the / (root) directory of the OSS file system, where ..(dot-dot) has the
same meaning as . (dot).
Guardian directories (that is, directories within the /G file system) behave the same as OSS direc-
tories, with the following exceptions:
• The mkdir() function successfully creates a directory within /G only when all of the fol-
lowing are true:
— The directory is exactly three directories under the root (for example,
/G/vol/subvol).
— The filenames in the directory pathname use correct Guardian naming syntax
(otherwise, errno is set to [EINVAL]).
— The directory corresponds to a Guardian subvolume.
• The mkdir() function succeeds on a directory that is an existing Guardian subvolume
(for example, /G/vol/subvol) only when the Guardian subvolume is empty. If the Guar-
dian subvolume is not empty, the mkdir() function fails and errno is set to the value
[EEXIST].
RELATED INFORMATION
Functions: chdir(2), closedir(3), mkdir(2), opendir(3), readdir(3), rewinddir(3), rmdir(2).
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