179 ################################################################

   180 # Useful functions.

   181 

   182 datediff() {

   183   [[ -n "$1" ]] || { echo first argument is missing; return 1; }

   184   [[ -n "$2" ]] || { echo second argument is missing; return 1; }

   185   local diff=$(( $(date -d "$2" +%s) - $(date -d "$1" +%s) ))

   186   local sec=$(( diff % 60 ))

   187   diff=$(( diff / 60 ))

   188   local min=$(( diff % 60 ))

   189   diff=$(( diff / 60 ))

   190   local hour=$(( diff % 24 ))

   191   local day=$(( diff / 24 ))

   192   echo $day days $hour hours $min minutes $sec seconds

   193 }

   194