| [9] | 1 | .TH VOL 1
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| 2 | .SH NAME
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| 3 | vol \- split input on or combine output from several volumes
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| 4 | .SH SYNOPSIS
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| 5 | .B vol
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| 6 | .RB [ \-rw1 ]
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| 7 | .RB [ \-b
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| 8 | .IR blocksize ]
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| 9 | .RB [ \-m
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| 10 | .IR multiple ]
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| 11 | .RI [ size ]
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| 12 | .I device
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| 13 | .SH DESCRIPTION
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| 14 | .B Vol
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| 15 | either reads a large input stream from standard input and distributes it
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| 16 | over several volumes or combines volumes and sends them to
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| 17 | standard output. The size of the volumes is determined automatically if
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| 18 | the device supports this, but may be specified before the
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| 19 | argument naming the device if automated detection is not possible or if
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| 20 | only part of the physical volume is used. The direction of the data is
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| 21 | automatically determined by checking whether the input or output of
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| 22 | .B vol
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| 23 | is a file or pipe. Use the
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| 24 | .B \-r
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| 25 | or
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| 26 | .B \-w
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| 27 | flag if you want to specify the direction explicitly, in shell scripts
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| 28 | for instance.
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| 29 | .PP
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| 30 | .B Vol
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| 31 | waits for each new volume to be inserted, typing return makes it continue.
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| 32 | If no size is explicitely given then the size of the device is determined
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| 33 | each time before it is read or written, so it is possible to mix floppies
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| 34 | of different sizes. If the size cannot be determined (probably a tape) then
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| 35 | the device is assumed to be infinitely big.
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| 36 | .B Vol
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| 37 | can be used both for block or character devices. It will buffer the data
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| 38 | and use a block size appropriate for fixed or variable block sized tapes.
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| 39 | .PP
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| 40 | .B Vol
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| 41 | reads or writes 8192 bytes to block devices, usually floppies. Character
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| 42 | devices are read or written using a multiple of 512 bytes. This multiple
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| 43 | has an upper limit of 32767 bytes (16-bit machine), 64 kb (32-bit), or even
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| 44 | 1 Mb (32-bit VM). The last partial write to a character device is padded
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| 45 | with zeros to the block size. If a character device is a tape device that
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| 46 | responds to the
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| 47 | .BR mtio (4)
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| 48 | status call then the reported tape block size will be used as the smallest
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| 49 | unit. If the tape is a variable block length device then it is read or
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| 50 | written like a block device, 8192 bytes at the time, with a minimum unit
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| 51 | of one byte.
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| 52 | .PP
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| 53 | All sizes may be suffixed by the letters
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| 54 | .BR M ,
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| 55 | .BR k ,
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| 56 | .BR b
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| 57 | or
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| 58 | .BR w
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| 59 | to multiply the number by mega, kilo, block (512), or word (2). The volume
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| 60 | size by default in kilobytes if there is no suffix.
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| 61 | .SH OPTIONS
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| 62 | .TP
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| 63 | .B \-rw
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| 64 | Explicitly specify reading or writing. Almost mandatory in scripts.
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| 65 | .TP
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| 66 | .B \-1
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| 67 | Just one volume, start immediately.
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| 68 | .TP
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| 69 | .BI \-b " blocksize"
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| 70 | Specify the device block size.
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| 71 | .TP
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| 72 | .BI \-m " multiple"
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| 73 | Specify the maximum read or write size of multiple blocks. The
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| 74 | .B \-b
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| 75 | and
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| 76 | .B \-m
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| 77 | options allow one to modify the block size assumptions that are made above.
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| 78 | These assumptions are
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| 79 | .B "\-b 1 \-m 8192"
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| 80 | for block devices or variable length tapes, and
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| 81 | .B "\-b 512 \-m 65536"
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| 82 | for character devices (32 bit machine.) These options will not override the
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| 83 | tape block size found out with an
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| 84 | .BR mtio (4)
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| 85 | call. The multiple may be larger then the default if
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| 86 | .B vol
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| 87 | can allocate the memory required.
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| 88 | .SH EXAMPLES
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| 89 | To back up a tree to floppies as a compressed tarfile:
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| 90 | .PP
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| 91 | .RS
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| 92 | tar cf \- . | compress | vol /dev/fd0
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| 93 | .RE
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| 94 | .PP
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| 95 | To restore a tree from 720 kb images from possibly bigger floppies:
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| 96 | .PP
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| 97 | .RS
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| 98 | vol 720 /dev/fd0 | uncompress | tar xfp \-
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| 99 | .RE
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| 100 | .PP
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| 101 | Read or write a device with 1024 byte blocks:
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| 102 | .PP
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| 103 | .RS
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| 104 | vol \-b 1k /dev/rsd15
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| 105 | .RE
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| 106 | .PP
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| 107 | Read or write a variable block length tape using blocking factor 20 as used
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| 108 | by default by many
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| 109 | .BR tar (1)
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| 110 | commands:
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| 111 | .PP
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| 112 | .RS
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| 113 | vol \-m 20b /dev/rst5
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| 114 | .RE
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| 115 | .PP
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| 116 | Note that
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| 117 | .B \-m
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| 118 | was used in the last example. It sets the size to use to read or write,
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| 119 | .B \-b
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| 120 | sets the basic block size that may be written in multiples.
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| 121 | .SH "SEE ALSO"
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| 122 | .BR dd (1),
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| 123 | .BR tar (1),
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| 124 | .BR mt (1),
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| 125 | .BR mtio (4).
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