Re: I/O edirection and dd

[lilydjwg <lilydjwg@xxxxxxxxx>]

On Sun, Apr 24, 2016 at 11:53:42AM +0200, Meino.Cramer@xxxxxx wrote:
> Hi,
> 
> with the pipe
> 
>     cat verylongfile | dd count=512 | file -
> 
> I want to get the type of file without reading it completly.
> 
> Unfortunately dd and cat are very chatty and print something like:
> 
> 512+0 records in
> 512+0 records out
> 262144 bytes (262 kB) copied, 0.00396828 s, 66.1 MB/s
> "Here comes the wanted output of the file command'
> [2]    32419 broken pipe  cat tmp.blend | 
>        32420 done         dd count=512 | 
>        32421 done         file -
> 
> 
> I want to get rid of all that - except for the printout of the
> 'file' command.
> 
> I tried several permutations and combinations of '{}", "2>&1" and 
> such but beside some additional syntax errors my success was very
> ....hrmmm....limited.
> 
> How can I acchieve what I want?
> 
> Thank you very much in advance for any help!

Why don't you let file read the file itself? file won't read the entire
file.

dd prints out information to stderr, so you can do

cat verylongfile | dd count=512 2>/dev/null | file -

cat isn't necessary in this case. You can just use redirection:

< verylongfile dd count=512 2>/dev/null | file -

And head -c256k will do the same as your dd command.

-- 
Best regards,
lilydjwg