dd errors with certain DVDs

[Rick Stevens]

On Wed, 2007-03-28 at 10:44 +1000, Cameron Simpson wrote:
> On 27Mar2007 16:54, Tony Nelson <tonynelson at georgeanelson.com> wrote:
> | dd if=/dev/dvd bs=2048 count=$(isosize -d 2048 /dev/dvd) | sha1sum
> 
> isosize is a binary! Ugh. The man page doesn't say: does it do anything
> more than my (fixed) "ls|awk" incantation?
> 
> Anecdote on bloat: I the good old days, /bin/true was an empty executable
> file, (i.e. a zero length shell script, which trivially succeeded). To
> my horrow, on the first real BSD system I used (SunOS 4) it was a shell
> script consisting of a comment containing the BSD copyright notice. Some
> years later on an AIX box I found than every thing had become worse;
> it was a binary!
> 
> So I'm wondering, is isosize a ludicrous piece of implementation overkill, or
> is it doing something special?

It does special things, like ignore the lead-in and lead-out sectors of
the image or device.  I wouldn't call it "bloat".  It does useful stuff.

----------------------------------------------------------------------
- Rick Stevens, Principal Engineer             rstevens at internap.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-          When all else fails, try reading the instructions.        -
----------------------------------------------------------------------