Re: [Bug-tar] tar -[0-7][lmh] ?

[Sergey Poznyakoff]

Glenn Gagné <address@hidden> wrote:

> I searched in many man pages, websites, FAQ, mailing-lists, etc. about
> TAR option to specify tape drive 
> properties -[0-7][lmh] but nowhere I can find how to use this option.

The [0-7] selects the device numbers, and the letter selects the desired
density: 'l' stands for low, 'm' stands for medium, and 'h' stands for
high.

This option is disabled by default.  To enable it, define 
DEFAULT_ARCHIVE at the configuration time (e.g. ./configure
DEFAULT_ARCHIVE=/dev/osst0l).  Configure uses this variable to deduce
the default archive prefix, and the way to select density.  If
DEFAULT_ARCHIVE ends in a digit and one of the letters 'l', 'm', 'h', then
these two characters are removed and the remaining string is taken as the
default device prefix.  In this case, the option -[0-7][lmh] will select
the device and density by appending the digit and the letter to the
configured device prefix, e.g.:

 -0l        will yield  /dev/osst0l
 -4m        will yield  /dev/osst4m

Otherwise, if DEFAULT_ARCHIVE ends in a digit only, this digit is
removed to obtain the default device prefix.  Then, -[0-7][lmh] works as
follows: the first digit gives base device number; depending on the
density letter, this number is increased by

  0        for 'l'  
  8        for 'm'
  16       for 'h'

(this increments can be changed at configure time by defining
LOW_DENSITY_NUM, MID_DENSITY_NUM, and HIGH_DENSITY_NUM,
correspondingly).

Then the obtained number is converted to ASCII and appended to the
device prefix. 

Regards,
Sergey