Path: utzoo!utgpu!attcan!uunet!lll-winken!ncis.tis.llnl.gov!helios.ee.lbl.gov!epb2.lbl.gov!envbvs
From: envbvs@epb2.lbl.gov (Brian V. Smith)
Newsgroups: comp.unix.wizards
Subject: Re: read(2) won't move TK50 past tape file mark
Keywords: ultrix tk50 unix tapes
Message-ID: <2721@helios.ee.lbl.gov>
Date: 24 May 89 21:45:57 GMT
References: <466@polyof.UUCP> <187@larry.sal.wisc.edu>
Sender: usenet@helios.ee.lbl.gov
Lines: 18

According to the manual entry for mtio(4) on Ultrix 3.0
(quoted w/o permission):

     ... 
     done with a tape ioctl call.  A zero byte count is returned
     when a tape mark is read, but another read will fetch the
     first record of the next tape file. When a file open for
     writing is closed, two end-of-files (EOF) are written.

Therefore, you could expect to get 0 bytes read for two reads 
(because of two possible EOF's on the tape), but after that it should 
read the next file.
I haven't tried it on our machines, but it looks like what you have 
run into is a real bug.

Brian Smith
Lawrence Berkeley Laboratory
bvsmith@lbl.gov