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February 24, 2017

Friday Fine-Tune: Opening Up MPE's Shell

Way back in the middle 1990s HP added the Posix shell to the HP 3000. The improvement meant customers who had Unix and MPE running in the same shop could train operators and managers with a single set of commands. Posix was a plus, making the 3000 appear more Unix-like (which seemed important at the time).

Over the years, however, Posix has been a feature waiting be discovered for most 3000 managers and operators. The computer's operating system was renamed from MPE/XL to MPE/iX just for this added Posix feature. But enough history; Posix is still on the 3000 and remains a powerful interface tool, an alternative to the CI interface that HP created for the system. You can even call Posix commands from the CI, a nifty piece of engineering when it can be done.

That's not always possible, though. A customer wanted to know how to "expand wildcard shells" using Posix. He tried from the CI and had this story to relate.

:LL /BACKUPS/HARTLYNE/S*
ls: File or directory is not found

So how do I do this? I need to be able to tell tar to archive all of the reels of a STD STORE set via a regexp. It does not work in tar, and it apparently does not in ls—so I speculate that there is something special about the innovation of Posix utilities from the CI that I am not aware of. What is it?

Jeff Vance, the 3000 CI guru at while at HP, replied "Wildcards on most (all) Unix systems, including Posix implementations, are done by the shell, not the individual programs or in-lined shell commands, like ls in your example. A solution is to run the shell and execute ll from within.

The magic Posix shell command to do the expansion:

Screen Shot 2017-02-27 at 11.22.22 PMAn interesting footnote if you've read this far: The Posix shell for the 3000 is one part of the operating system that was not built by HP. The shell was licensed by HP from MKS, and Hewlett-Packard paid royalties to MKS so Posix could work inside of MPE/iX. That was an issue that posed a potential snag for source code licensing from HP. But the outside license issues never ended up blocking emulation or source-license arrangements. Managers have used Posix on the 3000 as a way to get familiar with commands in Unix systems. In the great majority of instances, these commands are the same.

11:10 PM in Hidden Value, Homesteading | Permalink

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