Re: Problem using dd within bash script

[Bernhard Voelker]

On 04/29/2014 09:22 AM, Sebastian Rückerl wrote:
> dd if=$1 of=$2 bs=4M oflag=direct &
> dd_pid=$!
>
> control_c (){
>          echo "Aborting due to interrupt. Disk will most likely be useless."
>          kill -s KILL $dd_pid
>          trap - INT
>          kill -s INT $$
> }
> #
> # trap keyboard interrupt (control-c)
> trap 'control_c' INT
>
> while   ps ax | grep " $dd_pid "     # might also need  | grep -v grep  here
> do
>          kill -s USR1 $dd_pid
>          sleep 5
> done

The construct with "ps ax | ..." is rather fragile.

I'd use something like the following instead to get
the intermediate I/O statistics:

  while kill -s USR1 "$dd_pid" ; do
    sleep 5
  done

Further note that when dd ends, then the above 'sleep 5'
may extent the time of the script to finish by another
<=5 seconds (which may not be a problem in your case).

Have a nice day,
Berny