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ht(4) [v7 man page]

HT(4)							     Kernel Interfaces Manual							     HT(4)

NAME
ht - RH-11/TU-16 magtape interface DESCRIPTION
The files mt0, mt1, ... refer to the DEC RH/TM/TU16 magtape. When opened for reading or writing, the tape is not rewound. When closed, it is rewound (unless the 0200 bit is on, see below). If the tape was open for writing, a double end-of-file is written. If the tape is not to be rewound the tape is backspaced to just between the two tapemarks. A standard tape consists of a series of 512 byte records terminated by a double end-of-file. To the extent possible, the system makes it possible, if inefficient, to treat the tape like any other file. Seeks have their usual meaning and it is possible to read or write a byte at a time. Writing in very small units is inadvisable, however, because it tends to create monstrous record gaps. The last octal digit of the minor device number selects the drive. The middle digit selects a controller. The initial digit is even to select 800 BPI, odd to select 1600 BPI. If the 0200 bit is on (initial digit 2 or 3), the tape is not rewound on close. Note that the minor device number has no necessary connection with the file name, and in fact tp(1) turns the short name x into `/dev/mtx'. The mt files discussed above are useful when it is desired to access the tape in a way compatible with ordinary files. When foreign tapes are to be dealt with, and especially when long records are to be read or written, the `raw' interface is appropriate. The associated files may be named rmt0, ..., rmt7, but the same minor-device considerations as for the regular files still apply. Each read or write call reads or writes the next record on the tape. In the write case the record has the same length as the buffer given. During a read, the record size is passed back as the number of bytes read, provided it is no greater than the buffer size; if the record is long, an error is indicated. In raw tape I/O, the buffer must begin on a word boundary and the count must be even. Seeks are ignored. A zero count is returned when a tape mark is read; another read will fetch the first record of the next tape file. FILES
/dev/mt?, /dev/rmt? SEE ALSO
tp(1) BUGS
The magtape system is supposed to be able to take 64 drives. Such addressing has never been tried. Taking a drive off line, or running off the end of tape, while writing have been known to hang the system. If any non-data error is encountered, it refuses to do anything more until closed. In raw I/O, there should be a way to perform forward and backward record and file spacing and to write an EOF mark explicitly. HT(4)

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TM(4)							     Kernel Interfaces Manual							     TM(4)

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

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