man ping
/-f
n
-f Flood ping. For every ECHO_REQUEST sent a period ‘‘.’’ is printed, while for ever ECHO_REPLY
received a backspace is printed. This provides a rapid display of how many packets are being
dropped. If interval is not given, it sets interval to zero and outputs packets as fast as they
come back or one hundred times per second, whichever is more. Only the super-user may use this
option with zero interval.
