Less confusion with dd! Watch dd with pipe viewer (pv)
Here we run it as sudo, such that both sides of pipe are executed as root
sudo -- sh -c \'pv /path/to/disk.iso | dd of=/dev/disk2\'-- signifies end of parameters to sudo, -c tells sh to execute passed command.
* If we were instead to run sudo pv /path/to/file | dd of=/path/to/dest pv would be run as root, but dd would not, causing command to fail if calling user doesn't have write privileges to dest.