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From: sdyer%bbn-unix@sri-unix.UUCP
Newsgroups: net.unix
Subject: Re: Raw vs. block device.  I'm confused.
Message-ID: <15357@sri-arpa.UUCP>
Date: Mon, 9-Jan-84 13:06:06 EST
Article-I.D.: sri-arpa.15357
Posted: Mon Jan  9 13:06:06 1984
Date-Received: Sun, 15-Jan-84 01:24:27 EST
Lines: 20

From:  Steve Dyer <sdyer@bbn-unix>


In general, most UNIX magtape drivers use the following conventions with
the RAW device:

	read(fh, buf, nbytes) returns -1 when nbytes < physical record size

		otherwise,

	read(fh, buf, nbytes) returns the actual number of bytes in the record
		(i.e., it transfers only a single record, regardless of the
		 byte count.)

I have always ascribed the former behavior to a limitation of the controller;
it transfers a full record or nothing.

/Steve Dyer
sdyer@bbncca
decvax!bbncca!sdyer