abnjh.490 Tapes on Unix - (nf)

[rpw3 at fortune.UUCP]

#R:ecsvax:-213200:fortune:26900031:000:1822
fortune!rpw3    Mar 10 18:16:00 1984

Having been peripherally involved (as a user) in DEC's efforts several
years ago to put "magtape labeling" into TOPS-10, and recently locally
in putting cartridge tape into UNIX, I urge people who are doing work on
magtape handling to get/read/understand the ANSI Magtape Labeling Standard,
especially the appendix on implementation implications. Even though it
may seem "ancient" to many people, the issues, from single-volume-single-file
through multi-volume-multi-file, are clearly laid out and addressed by the
standard.

Personally, I agree that the "funny device name" approach just doesn't hack it.
If you want "transparency" (whatever that is), the "stty" model seems to be a
better one and more consistent with overall UNIX "style" (whatever THAT is).

What seems awkward about it under UNIX is that UNIX doesn't really have
the concept of a "job", as evidenced by the hassles people have talked about
in net.unix* recently about how to kill a background process when you log off.
Another example is the various hacks (including our own "stty ... savemodes")
to get "sticky" characteristics applied to terminals across several opens
and closes, but which revert to system standard on logout.

With the "job" notion, it becomes easier to have logout or daemon processes
undo whatever allocations and modifications you did to peripherals during
your session (unless you were the superuser changing the system defaults!).

Even so, the Bourne Shell "trap 0" can provide some flavor of "job":

	$ mytape=`mount -tape -density 1600 -tracks 9`
	$ trap "unmount -tape $mytape" 0
	$ ...
	$ cat myfile > $mytape
	$ ...
	$ <^D>
	<$mytape gets unmounted>

Rob Warnock

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