From: Robert Klemme <shortcutter@...>
Date: 2009-11-29T22:00:11+09:00
Subject: Re: Ruby byte access to disk sectors like dd does

On 28.11.2009 19:12, Bill Kelly wrote:
> From: "Robert Klemme" <shortcutter@googlemail.com>
>> On 11/28/2009 01:26 AM, Bill Kelly wrote:
>>> :)  Here's a stab at it... (it does work properly if the last
>>> read returns fewer than 16 bytes.)
>> What makes it stop working properly if the file size is a multiple of 16?
> 
> It works OK in either case, is what I was trying to say.  :)

Ah, OK.  Thanks for the clarification!

>>> ruby -e 'File.open("/dev/hdb", "rb") {|io| print(io.read(512))}' |
>>>  ruby -e 'i=0; while(x=ARGF.read(16)); puts("%08x %-32s %s" % [i, x.unpack("H*"), x.tr("^\040-\176",".")]); i+=16; end'
>> Why do you separate this in two processes?  I've munged it a bit...
> 
> Same reason dd and hexdump are separate programs.
> 
> http://www.faqs.org/docs/artu/ch01s06.html

Well, but in light of that neither a Ruby replacement of dd or hexdump 
is needed as they do exist already and do their job properly - and 
likely even more efficient than Ruby. :-)

<quiz-idea>
Write a program that reads binary files and outputs them in a similar 
format as "hexdump -C" integrating features of "dd": The program needs 
to be able to understand a series of paired options "--start X --length 
Y" and "--start X --end Z" (X, Y, Z of course being integer numbers with 
obvious properties) which denote the regions of the stream to read.  The 
program must be capable of reading from a pipe as well!  Bonus points 
for accepting parameter "--block-size B" which determines the size of 
chunks read in one read operation.  You may also invent any number of 
additional options which control formatting of the output.  Source code 
must be shorter than 20 lines of code per additional option. ;-)
</quiz-idea>

Kind regards

	robert

-- 
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