[ale] dd and cat

[Eric Z. Ayers]

dd reads and writes in 'block' sizes that you specify.  This might be
better for performance reasons, (it is usually more efficient to copy
in big blocks rather than small blocks.)  I don't know what size cat
uses.  Plus, dd will copy exactly the number of bytes you ask it to.  
Cat just stops when you hit EOF.

One place where dd makes a big difference is in reading and writing to
tape. the number of bytes in each write() system call can affect how
big the blocks are that are written to tape.  

-Eric.


Ben Phillips writes:
 > If I want to replicate, say, a floppy disk, I can do it with 'cat /dev/fd0 >
 > image' followed by repeated instances of 'cat image > /dev/fd0'.
 > 
 > But the recommended way to do that is usually with 'dd' instead.  Why?  What
 > do they do different?
 > 
 > 
 >                       __   _                 
 > Ben Phillips         /  '_' )         ,,,    "Bulls do not win bull fights;
 > pynk at cc.gatech.edu   |  | ()|||||||||[:::)    people do.  People do not win
 >                      \__.-._)         '''     people fights; lawyers do."
 >                                                    -- Norman Augustine
 > 
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