There's one good (?) reason to use dd with devices: it specifies target in the same command. For devices, writing to them usually requires root privileges, so it's easy to:
sudo dd .... of=/dev/...
But there's no trivial cat equivalent:
sudo cat ... > target
Will open target as your current user anyway. You can play around with tee and redirection of course. But that's getting more complicated than the original.
This is admittedly somewhat esoteric, but it seems like a stretch to say `dd` does not have some place, especially when transferring binary data in very specific ways.
Since we're sharing shell tricks: The "sudo tee > /dev/null" may be baroque, but I find it useful whenever I start editing stuff in /etc in vim, only to find that I cannot write my changes because I'm not root. In that case,
:w !sudo tee %
does the trick. (What "w!" does is send the buffer into the given shell command as stdin.)
Basically, you can use cp wherever you use dd, as long as you're not changing any low-level parameters (e.g. starting 500 bytes into the file or something).
Yes. Yes it does. Reminds me of a Sunday evening in the late 90ies when I stopped working as root all the time:
cp backup.tar.bz /dev/sda
Nowadays I would know enough to at least get the contents of the backup.tar.bz back. Back then, this was the end of both my / partition (or any other partition) and the backup of my music collection.
Still, that didn't end my love affair with Unix. It did make me a whole lot more careful though.
Well that's strictly a bug caused by mistaken use, as strings are not expanded lazily and heredocs are just another string syntax. How can one use the unix shell without string interpolation? Also, a similar programme would give the wrong result in, say, Ruby or Perl too.
