[unix-history] / usr / man / man4 / tm.4

.TH TM 4 
.SH NAME
tm \- TM-11/TU-10 magtape interface
.SH DESCRIPTION
The files
.I "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.
.PP
If the 0200 bit is on in the minor device number the
tape is not rewound when closed.
.PP
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 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.
.PP
The
.I 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
.I "rmt0, ..., rmt7."
Each
.I read
or
.I 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.
.SH FILES
/dev/mt?,
/dev/rmt?
.SH "SEE ALSO"
tp(1)
.SH 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.
Commit	Line	Data
70b96c2d DR	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 closed it can be rewound or not, see below.
	9	If it was open for writing, two end-of-files are written.
	10	If the tape is not to be rewound
	11	it is positioned with the head between the two
	12	tapemarks.
	13	.PP
	14	If the 0200 bit is on in the minor device number the
	15	tape is not rewound when closed.
	16	.PP
	17	A standard tape consists of a
	18	series of 512 byte records terminated by an
	19	end-of-file.
	20	To the extent possible, the system makes
	21	it possible, if inefficient, to treat
	22	the tape like any other file.
	23	Seeks have their usual meaning and it is possible
	24	to read or write a byte at a time.
	25	Writing in very small units is inadvisable,
	26	however, because it tends to create monstrous record
	27	gaps.
	28	.PP
	29	The
	30	.I mt
	31	files discussed above are useful
	32	when it is desired to access the tape in a way
	33	compatible with ordinary files.
	34	When foreign tapes are to be dealt with, and especially
	35	when long records are to be read or written, the
	36	`raw' interface is appropriate.
	37	The associated files are named
	38	.I "rmt0, ..., rmt7."
	39	Each
	40	.I read
	41	or
	42	.I write
	43	call reads or writes the next record on the tape.
	44	In the write case the record has the same length as the
	45	buffer given.
	46	During a read, the record size is passed
	47	back as the number of bytes read, provided it is no greater
	48	than the buffer size;
	49	if the record is long, an error is indicated.
	50	In raw tape I/O, the buffer must begin on a word boundary
	51	and the count must be even.
	52	Seeks are ignored.
	53	A zero byte count is returned when a tape mark is read,
	54	but another read will fetch the first record of the
	55	new tape file.
	56	.SH FILES
	57	/dev/mt?,
	58	/dev/rmt?
	59	.SH "SEE ALSO"
	60	tp(1)
	61	.SH BUGS
	62	If any non-data error is encountered, it refuses to do anything
	63	more until closed.
	64	In raw I/O, there should be a way
65	to perform forward and backward record and file spacing and
66	to write an EOF mark.