shell取余數

date取得分鍾數
$(()) 運算

#execute every 5 minutes
a=`date +%M`
b=$(( $a % 5 ))
if [ $b = 0 ] ; then 
       echo "execute it"
else
       echo "Not execute"
fi

 https://www.cnblogs.com/archoncap/p/4886765.html