.TH VOL 1.SH NAMEvol \- split input on or combine output from several volumes.SH SYNOPSIS.B vol.RB [ \-rw1 ].RB [ \-b.IR blocksize ].RB [ \-m.IR multiple ].RI [ size ].I device.SH DESCRIPTION.B Voleither reads a large input stream from standard input and distributes itover several volumes or combines volumes and sends them tostandard output.  The size of the volumes is determined automatically ifthe device supports this, but may be specified before theargument naming the device if automated detection is not possible or ifonly part of the physical volume is used.  The direction of the data isautomatically determined by checking whether the input or output of.B volis a file or pipe.  Use the.B \-ror.B \-wflag if you want to specify the direction explicitly, in shell scriptsfor instance..PP.B Volwaits for each new volume to be inserted, typing return makes it continue.If no size is explicitely given then the size of the device is determinedeach time before it is read or written, so it is possible to mix floppiesof different sizes.  If the size cannot be determined (probably a tape) thenthe device is assumed to be infinitely big..B Volcan be used both for block or character devices.  It will buffer the dataand use a block size appropriate for fixed or variable block sized tapes..PP.B Volreads or writes 8192 bytes to block devices, usually floppies.  Characterdevices are read or written using a multiple of 512 bytes.  This multiplehas an upper limit of 32767 bytes (16-bit machine), 64 kb (32-bit), or even1 Mb (32-bit VM).  The last partial write to a character device is paddedwith zeros to the block size.  If a character device is a tape device thatresponds to the.BR mtio (4)status call then the reported tape block size will be used as the smallestunit.  If the tape is a variable block length device then it is read orwritten like a block device, 8192 bytes at the time, with a minimum unitof one byte..PPAll sizes may be suffixed by the letters.BR M ,.BR k ,.BR bor.BR wto multiply the number by mega, kilo, block (512), or word (2).  The volumesize by default in kilobytes if there is no suffix..SH OPTIONS.TP.B \-rwExplicitly specify reading or writing.  Almost mandatory in scripts..TP.B \-1Just one volume, start immediately..TP.BI \-b " blocksize"Specify the device block size..TP.BI \-m " multiple"Specify the maximum read or write size of multiple blocks.  The.B \-band.B \-moptions allow one to modify the block size assumptions that are made above.These assumptions are.B "\-b 1 \-m 8192"for block devices or variable length tapes, and.B "\-b 512 \-m 65536"for character devices (32 bit machine.)  These options will not override thetape block size found out with an.BR mtio (4)call.  The multiple may be larger then the default if.B volcan allocate the memory required..SH EXAMPLESTo back up a tree to floppies as a compressed tarfile:.PP.RStar cf \- . | compress | vol /dev/fd0.RE.PPTo restore a tree from 720 kb images from possibly bigger floppies:.PP.RSvol 720 /dev/fd0 | uncompress | tar xfp \-.RE.PPRead or write a device with 1024 byte blocks:.PP.RSvol \-b 1k /dev/rsd15.RE.PPRead or write a variable block length tape using blocking factor 20 as usedby default by many.BR tar (1)commands:.PP.RSvol \-m 20b /dev/rst5.RE.PPNote that.B \-mwas used in the last example.  It sets the size to use to read or write,.B \-bsets the basic block size that may be written in multiples..SH "SEE ALSO".BR dd (1),.BR tar (1),.BR mt (1),.BR mtio (4).