1TM(4) Kernel Interfaces Manual TM(4)
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6 tm - TM-11/TU-10 magtape interface
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9 The files mt0, ..., mt7 refer to the DEC TU10/TM11 magtape. When
10 closed it can be rewound or not, see below. If it was open for writ‐
11 ing, two end-of-files are written. If the tape is not to be rewound it
12 is positioned with the head between the two tapemarks.
13 If the 0200 bit is on in the minor device number the tape is not
15 rewound when closed.
16 A standard tape consists of a series of 512 byte records terminated by
18 an end-of-file. To the extent possible, the system makes it possible,
19 if inefficient, to treat the tape like any other file. Seeks have
20 their usual meaning and it is possible to read or write a byte at a
21 time. Writing in very small units is inadvisable, however, because it
22 tends to create monstrous record gaps.
23 The mt files discussed above are useful when it is desired to access
25 the tape in a way compatible with ordinary files. When foreign tapes
26 are to be dealt with, and especially when long records are to be read
27 or written, the `raw' interface is appropriate. The associated files
28 are named rmt0, ..., rmt7. Each read or write call reads or writes the
29 next record on the tape. In the write case the record has the same
30 length as the buffer given. During a read, the record size is passed
31 back as the number of bytes read, provided it is no greater than the
32 buffer size; if the record is long, an error is indicated. In raw tape
33 I/O, the buffer must begin on a word boundary and the count must be
34 even. Seeks are ignored. A zero byte count is returned when a tape
35 mark is read, but another read will fetch the first record of the new
36 tape file.
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39 /dev/mt?, /dev/rmt?
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42 tp(1)
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45 If any non-data error is encountered, it refuses to do anything more
46 until closed. In raw I/O, there should be a way to perform forward and
47 backward record and file spacing and to write an EOF mark.
48 TM(4)