In the event that the input is from a stream which has a known size, it would be nice to provide a method to provide the size to dcfldd for time estimation purposes. This patch implements this as an extension to the sizeprobe= option.
In the event that sizeprobe=XXX is provided and XXX is neither if or of, it attempts to parse the value as a number in the same method as bs, etc (allowing suffixes).
A situation where this would be useful is when a split file is going to be restored. The size can be provided (either precisely or by estimate):
dcfldd if=/dev/sda sizeprobe=if split=1G of=test
cat test* | dcfldd of=/dev/sdb sizeprobe=100G
where sda is 100G and sdb is not (else, it would be possible to use sizeprobe=of).