Hierarchical file system (HFS)

As of Release 4.5, the MPE/iX file system is hierarchical (tree structured) and can contain files at many different levels. This organization provides a special kind of file called a directory. Instead of holding data, directories contain lists of files and pointers to those files. A directory can also contain other directories. This organization is similar to the file systems on UNIX® or MS-DOS® systems.

The new file organization still includes the familiar accounts, groups, and users. The hierarchical file system (called HFS, for short) extends the traditional MPE file system features so the operating system is more flexible.

You're used to referring to files, groups, and accounts using the traditional MPE syntax: FILE1.PUB.SYS. You can still use MPE syntax. You can also make use of a new syntax called HFS syntax, which looks like this: /SYS/PUB/FILE1.

The MPE/iX Release 4.5 enhancements are compared to previous releases in Table 1-1 “Where Accounts, Groups, Directories, and Files Can Be Located”.

shows how you can organize files, accounts, groups, and directories in the file system. Notice that accounts, directories, groups, and files all connect back to one directory designated by a "/" (slash). This is referred to as the root or the root directory.

Figure 1-4 MPE/iX File System Example

HFS file names

MPE/iX Release 4.5 allows you to assign longer file names than in previous versions of MPE/iX. Table 1-2 “Maximum Lengths of Account, Group, Directory, and File Names” summarizes name lengths for accounts, groups, directories, and files previous to Release 4.5 and after Release 4.5.

Table 1-2 Maximum Lengths of Account, Group, Directory, and File Names

Type	MPE Syntax	HFS Syntax
Account name	8 uppercase characters	8 uppercase characters
Group name	8 uppercase characters	8 uppercase characters
Directory name	Not available	16 mixed case characters (if directly under root or directly under a group). Up to 255 characters (elsewhere).
File name	8 uppercase characters	16 mixed case characters (if directly under root or directly under a group). Up to 255 characters (elsewhere).

 

HFS syntax

Table 1-3 “Syntax Summary” summarizes some of the syntax enhancements introduced by the MPE hierarchical file system. The syntax that you are used to still works for files in groups and accounts. So to use HFS syntax, you must precede file and directory names with ./ or /. Otherwise, MPE/iX treats the names using traditional MPE syntax rules.

This manual refers to files that are named using HFS syntax as HFS files.

Table 1-3 Syntax Summary

Item	MPE Syntax	HFS Syntax
Specify file name	No special beginning character required: FILE.GRP.ACCT	Name must be preceded by a ./ (dot slash) or / (slash): /ACCT or ./dir1
Name separators	. (period); / separates lockwords	/ (slash)
Way of specifying files	Bottom up: FILE.GRP.ACCT	Top down: /ACCT/GRP/FILE
Case sensitivity	Not case sensitive; all characters are shifted to uppercase	Case sensitive: /DIR/FILE1 and /DIR/file1 are two different files
Special characters	Only alphanumeric characters	Alphanumeric, - (hyphen), . (dot), and _ (underscore) are allowed
First character	Must be alphabetic	Can be alphanumeric, _ (underscore), or . (dot) but not - (hyphen)