shell 练习（function,case,for,select）

#!/bin/bashsquare(){        echo "Please input the num:"        read num1        let "squ=num1*num1"        echo "Square of $num1 is $squ"}cube(){        echo "Please input the num:"        read num2        let "c=num2*num2*num2"        echo "Cube of $num2 is $c"}power(){        echo "Please input the num:"        read num3        echo "Please input the power:"        read p        let "temp=1"        for(( i=1;i<=$p;i++ ))        do                let "temp=temp*num3"        done        echo "power $p of $num3 is $temp."}choice(){        select i in "square" "Cube" "Power"        do                break;        done        echo "you select is $i"        case $i in        square)                square        ;;        Cube)                cube        ;;        Power)                power        ;;        *)                echo "select item is not exist"        esac}choice