Path: utzoo!attcan!uunet!munnari.oz.au!uniwa!wacsvax!cutmcvax!architec
From: architec@cutmcvax.OZ (Phil Dench )
Newsgroups: comp.sys.sgi
Subject: appending to tape archives
Keywords: 1/4" mag tapes, appending
Message-ID: <127@cutmcvax.OZ>
Date: 9 Apr 90 17:20:22 GMT
Reply-To: architec@cutmcvax.oz (Phil Dench )
Organization: Curtin University of Technology, Maths & Comp Sc
Lines: 38

All this talk about mag tapes has reminded me to post the following.

Does anyone know how to append to existing data on a 1/4" streamer
cartridge mag tape?

I used to be able to do this under 3.1 (but always suspected it was a
bug not a feature) ...

    fd = check_open( "/dev/tape", O_WRONLY | O_APPEND);

... and any subsequent writes would happily append.

Now under 3.2 this just overwrites the first file on the tape.
Anything else I try does the same sort of thing. I cant even do a fsf
then a write because of (from mtio(1)) ...

    A tape is normally open for reading and/or writing, but a tape
    cannot be read and written simultaneously.  After a rewind, an
    unload, or an MTAFILE ioctl, writes may follow reads and
    vice-versa ...

A rewind is no good to me. MTAFILE doesn't work on a 1/4".  And am I
correct in assuming the unload is just an 'mt offline'?

It would be real useful if I could append.  Cartridge tapes cost $60
Australian here.  I don't want to use one for each little project that
I'm archiving.  And I dont really want to restore all the old ones on a
tape just to write them all back with a new one on the end.

    Phil Dench

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