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From: naftoli@aecom.UUCP (Robert N. Berlinger)
Newsgroups: net.bugs.usg
Subject: Re: Re: bug in System Vr2 volcopy(1M)
Message-ID: <1180@aecom.UUCP>
Date: Sun, 24-Feb-85 14:51:53 EST
Article-I.D.: aecom.1180
Posted: Sun Feb 24 14:51:53 1985
Date-Received: Wed, 27-Feb-85 21:06:45 EST
References: <1169@aecom.UUCP> <8407@brl-tgr.ARPA>
Distribution: net
Organization: Albert Einstein Coll. of Med., NY
Lines: 16

> > ...  I see no apparent fix, since the System V tape driver does
> > not have ioctl calls to skip around the tape with.
> 
> On UNIX System V one does not need ioctls to position the tape.
> </dev/mt/whatever	does a file skip, if non-rewinding device,
> 			otherwise rewinds.
> read() can be used to do a block skip in the rare case that it's
> needed.

Although the use of rewind and no-rewind devices helps,
there is no way to skip backwards a file or record, which is
necessary if you want to do relative positioning rather than absolute
which is what is needed in the volcopy case.
-- 
Robert Berlinger
...{philabs,cucard,pegasus,ihnp4,rocky2}!aecom!naftoli