HP 3000 Manuals HP 3000 Manuals
Hierarchical Directory Files
The following sections provide information about hierarchical directory
files of interest to application developers who wish to use MPE/iX system
intrinsics to manage their applications within the hierarchical directory
structure.
The traditional MPE directory structure
A directory is a repository of information about objects on a computer
system. Objects can be either files or directories. Directory services
are a set of routines that manipulate directory objects and retrieve
information about the objects found in a directory.
Prior to MPE/iX Release 4.5, the MPE/iX directory structure organized the
file system as a four-level hierarchy:
* The root directory. This directory was never exposed to the user.
* Accounts, or account directories, immediately under the root
directory. Only group directories were allowed under account
directories.
* Groups, or group directories, at the level immediately under
account directories. Only files are allowed under group
directories.
* Files at the level immediately under group directories.
This traditional MPE directory structure was implemented to meet the
demands of the commercial business community and continues to serve as an
excellent directory structure.
Beginning with MPE/iX Release 4.5, the directory structure has been
greatly enhanced with the introduction of the MPE/iX hierarchical
directory structure. The challenge Hewlett-Packard faced was to provide
an "open" directory structure while preserving the traditional MPE
directory structure.
This has been accomplished by successfully integrating MPE/iX
hierarchical directory structure within and around the traditional MPE
directory structure, thus providing the benefits of both directory
structures to existing and new users.
NOTE All existing applications provided on HP 3000 Series 900 computer
systems continue to function exactly as they have in the past. In
the future, more and more applications will be available that take
advantage of the new MPE/iX hierarchical directory structure. This
includes both POSIX-conformant applications as well as existing
applications enhanced to take advantage of MPE/iX "Open" features.
MPE/iX hierarchical directory structure features
The new MPE/iX hierarchical file system directory services organize the
file system as a file hierarchy. The HFS file system hierarchy
conceptually resembles a tree. In the hierarchy, files are grouped
together as leaf nodes in name contexts called directories.
Files and directories are referred to using a pathname that describes
their location in the file system hierarchy relative to either a
process's root directory (absolute pathname) or current working directory
(relative pathname).
A process's current working directory may change during the lifetime of a
process. Files may have exactly one pathname relative to the system's
root directory (the absolute pathname). Each file name reference is
known as a link.
MPE/iX hierarchical directory services present an integrated view of the
file system. There exists a common root for all directories (exposing
the traditional MPE root directory to users).
Traditional MPE accounts and groups are considered in the HFS context to
be directories. However, they are special directory structures that
include hierarchical directory behavior while continuing to serve within
the MPE framework.
Following are special features of the MPE/iX root directory and MPE/iX
account and group directories to ensure both backward compatibility and
forward benefit.
Root directory features.
* The MPE/iX root directory (/) cannot be renamed, copied, or
purged.
* Only users with SM capability can create objects directly under
the root directory.
* Access permissions for the root directory are RD (read directory)
and TD (traverse directory) for all users and CD (create directory
entries) and DD (delete directory entries) for none. Attempts to
remove or change access permissions of the root directory result
in an error.
* Names of files and hierarchical directories created directly under
the root directory are restricted to 16 characters in length.
* The root directory is restricted to the MPE/iX system volume set.
* The root directory does not contain explicit dot (.) and dot-dot
(..) directories; however, dot and dot-dot directory behavior is
supported.
* The user ID (UID) and group ID (GID) associated with the root
directory cannot be modified.
Account directory features.
* MPE/iX accounts can be created directly under the root directory
only by a user with SM capability using the MPE/iX NEWACCT
command. MPE/iX accounts cannot be created, renamed, copied, or
purged through the MPE/iX shell.
* GID = account name
* Access permissions for an MPE/iX account are RD & TD for all users
and CD & DD for none. Attempts to use the ALTSEC command or chmod
MPE/iX shell command to remove access permissions of an MPE/iX
account result in an error.
* When an MPE/iX account name is a component in an HFS pathname, it
must be specified in uppercase.
* MPE/iX accounts are restricted to the MPE/iX system volume set.
* MPE/iX accounting limits for disk space apply to both hierarchical
directories and files located at all levels under MPE/iX groups.
* An MPE/iX account does not contain explicit dot and dot-dot
directories; however, dot and dot-dot directory behavior is
supported.
* The user ID (UID) and group ID (GID) associated with an MPE/iX
account cannot be modified.
* Names of files and directories created under accounts are limited
to 16 characters.
Group directory features.
* MPE/iX groups can be created directly under MPE/iX accounts only
by a user with SM capability or a user with AM capability who is a
member of that account (whose GID matches the GID of the account),
using the MPE/iX NEWGROUP command. They can be modified using the
ALTGROUP command. MPE/iX groups cannot be created, modified, or
purged through the MPE/iX shell.
* Default access permissions for MPE/iX groups are RD & TD for all
users and CD access for none. Attempts to remove access
permissions of an MPE/iX group result in an error. An MPE/iX
group must have MPE/iX save access assigned to it before files and
directories can be created at any level under it. For more
information about MPE/iX save access, refer to the manual
Manager's Guide to MPE/iX Security (32650-90474).
* When an MPE/iX group name is a component in an HFS pathname, it
must be specified in uppercase.
* GID inheritance from ACCOUNT.
* Names of files and hierarchical directories created directly under
MPE/iX groups are restricted to 16 characters in length.
* MPE/iX groups (and, indirectly, all files and hierarchical
directories at all levels under them) can optionally be assigned
to a user volume set.
* MPE/iX accounting limits for disk space apply to both hierarchical
directories and files located at all levels under MPE/iX groups.
* An MPE/iX group does not contain explicit dot and dot-dot
directories; however, dot and dot-dot directory behavior is
supported.
* The user ID (UID) and group ID (GID) associated with an MPE/iX
group cannot be modified.
Hierarchical directory features.
* Hierarchical directories cannot be copied. Hierarchical
directories can be purged only when they are empty (containing
only the dot and dot-dot directory entries).
* HFS directories can be renamed through the POSIX.1 rename
function, or through the shell MV command. The renaming of a
directory must be within the same disk space accounting domain.
* Users can define and modify access permissions for hierarchical
directories.
* The group ID (GID) of a hierarchical directory is inherited from
its parent directory. The user ID (UID) of a hierarchical
directory is inherited from the user who created it. The UID and
GID of a hierarchical directory can be modified using the ALTSEC
command or the MPE/iX shell chown command.
* Hierarchical directories (and all objects under them) that are not
under MPE/iX groups are restricted to the MPE/iX system volume
set.
* Names of hierarchical directories and files located directly under
either the system's root directory or MPE/iX accounts or groups
are restricted to 16 characters in length.
* Names of files and hierarchical directories created directly under
a hierarchical directory are restricted to 255 characters in
length.
* Hierarchical directories contain explicit dot and dot-dot
directory entries.
MPE/iX hierarchical directory services can access any file in the file
system hierarchy including files in the traditional MPE directory
structure using HFS syntax. For example, both of the following fully
qualified file name specifications refer to the same file.
MYFILE.MYGROUP.MYACCT
/MYACCT/MYGROUP/MYFILE
Hierarchical directory files
Beginning with MPE/iX Release 4.5, the directory file type is available
to allow an MPE/iX file to reproduce POSIX directory file behavior.
The POSIX standard defines a directory to be a special file that contains
directory entries of all files and directories located directly beneath
it. Users can create directories and read directory entries but cannot
directly write to directory files. Instead, the system creates a new
directory entry each time a file is created and placed in that directory,
and it removes the entry when the file either purged or moved to a
different directory.
NOTE In this manual, the term "hierarchical directory" is used to refer
to an MPE/iX disk file whose file type is directory, and its record
type is the hierarchical directory record type.
Creating a hierarchical directory
You use the HPFOPEN intrinsic to create a hierarchical directory. The
FOPEN intrinsic can open an existing hierarchical directory but cannot
create one because the foptions parameter cannot be extended to specify a
file type of directory or a record format type of hierarchical directory.
The following table defines the file and access attributes imposed on a
hierarchical directory when it is created. These attributes cannot be
changed during the life of the hierarchical directory.
Table 4-2. HFS Directory File Attributes and/or Access Options
--------------------------------------------------------------------------------------------
| | |
| Attribute Name | Default |
| | |
--------------------------------------------------------------------------------------------
| | |
| File type | Directory (DIR) disk file. Must be explicitly specified in |
| | order to create a hierarchical directory. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Dynamic locking | Disabled. Any value other than 0 will result in error. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Exclusive | Shared. Any attempt to open with exclusive access(1) will |
| | result in error. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Nowait I/O | Disabled. Any attempt to open nowait(1) will result in error. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Record format | Hierarchical directory. All other specifications are ignored. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Domain | Create as a permanent file. All other specifications are |
| | ignored. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Carriage control | Specifying cctl will result in error. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Access type | Directory read access. Must be explicitly specified to create a |
| | hierarchical directory. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Multirecord | Multirecord access (MULTI). All other specifications are |
| | ignored. |
| | |
--------------------------------------------------------------------------------------------
| | |
| ASCII/binary | ASCII. All other specifications are ignored. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Remote environment | Remote access to hierarchical directories is not supported. |
| | Specifying this option results in an error. |
| | |
--------------------------------------------------------------------------------------------
| | |
| File size | Two gigabytes. Specifying a file size will result in error. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Copy mode | Ignored. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Record size | 32 bytes. Any value specified will be ignored. |
| | |
--------------------------------------------------------------------------------------------
| | |
| File code | Specifying any value will result in error. |
| | |
--------------------------------------------------------------------------------------------
| | |
| Number of buffers | Ignored. |
| | |
--------------------------------------------------------------------------------------------
| | |
| User labels | Not allowed. Attempting to specify this option results in an |
| | error. |
| | |
--------------------------------------------------------------------------------------------
| | |
| File equations | Only applicable with MPE namespace directories. |
| | |
--------------------------------------------------------------------------------------------
The dot (.) and dot-dot (..) directories
When a hierarchical directory is first created, two special directory
files are placed in the directory:
* The dot (.) directory entry is an alternative way to specify the
directory itself without having to use a formal directory file
name.
* The dot-dot (..) directory is an alternative way to specify the
directory's parent directory without having to use a formal
directory file name.
The dot and dot-dot directories provide additional navigation aids to a
process. Applications using the dot and dot-dot directories to express a
directory or parent directory need not be concerned with their absolute
location on the system.
The dot and dot-dot directories can be opened just like any other
hierarchical directory. File information intrinsics can be used to
return information about these directories. However, the dot and dot-dot
directories cannot be modified by a user. In addition, these two
directories cannot be explicitly purged except by purging the directory
they live in.
NOTE The dot and dot-dot directories are not found explicitly under the
root directory or under MPE/iX accounts and MPE/iX groups; however,
dot and dot dot behavior is supported.
Opening a hierarchical directory
Both HPFOPEN and FOPEN can be used to open an existing hierarchical
directory.
Record selection and data transfer
The HPFOPEN intrinsic provides the "read directory" access option when
creating or opening a directory, but there are no system intrinsics that
allow you to either read from or write to a directory. Note that POSIX
interfaces exist to read directory entries from directories. The system
itself manages a directory file, managing read access during pathname
resolution and write access when new files are either created or purged
in the hierarchical directory.
The FCONTROL intrinsic item number 5 "rewind" option allows you to rewind
a hierarchical directory entry pointer to the first entry of the
directory.
Getting hierarchical directory information
The following file information intrinsics provide support for
hierarchical directory files:
FFILEINFO Item numbers 3, 52, 53, 54, and 55 have been
enhanced to return information about hierarchical
directories. Item numbers 80 through 91 are new.
FGETINFO FFILEINFO is the recommended intrinsic for
returning information on a hierarchical directory
(or any file, for that matter). The foptions
parameter of FGETINFO cannot return the file type
or record format of a hierarchical directory.
FLABELINFO Item numbers 6, 7, 8, 13, 20, and 21 have been
enhanced to return information about hierarchical
directories. Item numbers 37 through 49 are new.
PRINTFILEINFO Enhanced to display information about an open
hierarchical directory. For more information,
refer to "Listing File Information" later in this
chapter.
Closing or purging a hierarchical directory
The FCLOSE intrinsic has been enhanced to allow you to close a
hierarchical directory, but the directory must be closed in the permanent
file domain. For more information, refer to the section "Closing a File"
later in this chapter.
You cannot purge a hierarchical directory that has entries in it other
than the dot and dot-dot directory entries. You must first purge all
objects under a hierarchical directory before you can purge that
directory.
The only exception to this rule is when you use the PURGEGROUP command
from the MPE/iX CI to purge an MPE/iX group directory, or the PURGEACCT
command to purge an MPE/iX account directory (and all groups under it).
When this occurs, all hierarchical directories located under the purged
groups are automatically purged, whether or not they contain entries.