Commit | Line | Data |
---|---|---|
2c2d3e6c TL |
1 | .TH TM 4 |
2 | .SH NAME | |
3 | tm \- TM-11/TU-10 magtape interface | |
4 | .SH DESCRIPTION | |
5 | The files | |
6 | .I "mt0, ..., mt7" | |
7 | refer to the DEC TU10/TM11 magtape. | |
8 | When opened for reading or writing, | |
9 | the tape is rewound. | |
10 | When closed, it is rewound; | |
11 | if it was open for writing, an end-of-file is written first. | |
12 | .PP | |
13 | A standard tape consists of a | |
14 | series of 512 byte records terminated by an | |
15 | end-of-file. | |
16 | To the extent possible, the system makes | |
17 | it possible, if inefficient, to treat | |
18 | the tape like any other file. | |
19 | Seeks have their usual meaning and it is possible | |
20 | to read or write a byte at a time. | |
21 | Writing in very small units is inadvisable, | |
22 | however, because it tends to create monstrous record | |
23 | gaps. | |
24 | .PP | |
25 | The | |
26 | .I mt | |
27 | files discussed above are useful | |
28 | when it is desired to access the tape in a way | |
29 | compatible with ordinary files. | |
30 | When foreign tapes are to be dealt with, and especially | |
31 | when long records are to be read or written, the | |
32 | `raw' interface is appropriate. | |
33 | The associated files are named | |
34 | .I "rmt0, ..., rmt7." | |
35 | Each | |
36 | .I read | |
37 | or | |
38 | .I write | |
39 | call reads or writes the next record on the tape. | |
40 | In the write case the record has the same length as the | |
41 | buffer given. | |
42 | During a read, the record size is passed | |
43 | back as the number of bytes read, provided it is no greater | |
44 | than the buffer size; | |
45 | if the record is long, an error is indicated. | |
46 | In raw tape I/O, the buffer must begin on a word boundary | |
47 | and the count must be even. | |
48 | Seeks are ignored. | |
49 | A zero byte count is returned when a tape mark is read, | |
50 | but another read will fetch the first record of the | |
51 | new tape file. | |
52 | .SH FILES | |
53 | /dev/mt?, | |
54 | /dev/rmt? | |
55 | .SH "SEE ALSO" | |
56 | tp(1) | |
57 | .SH BUGS | |
58 | If any non-data error is encountered, it refuses to do anything | |
59 | more until closed. | |
60 | In raw I/O, there should be a way | |
61 | to perform forward and backward record and file spacing and | |
62 | to write an EOF mark. |