while循环中的连续输入会不断重复？

Question

我创建了一个充当简单计算器的bash脚本。 计算器的目标是不断询问用户输入。 该输入包括操作和两个数字。

但是，我遇到了一个问题，在提交第一个操作后， while循环将继续执行该初始操作。

码：

#!/bin/bash
echo "Calculator"
echo "Input an Operation: +, -, *, /, and % (0 to stop): "
read OP

while [ $OP != "0" ]
do
    if [ $OP == "+" ]; then
        echo "Add Numbers"
        SUM=0
        echo "Enter number1: "
        read N1

        echo "Enter number2: "
        read N2

        SUM=$((N1+N2))

        echo "Result: $SUM"
    elif [ $OP == "-" ]; then
        echo "Subtract Numbers"
        SUB=0
        echo "Enter number1: "
        read N1

        echo "Enter number2: "
        read N2

        SUB=$((N1-N2))

        echo "Result: $SUB"
    elif [ $OP == "*" ]; then
        echo "Multiple Numbers"
        MUL=0
        echo "Enter number1: "
        read N1

        echo "Enter number2: "
        read N2

        MUL=$((N1*N2))

        echo "Result: $MUL"
    elif [ $OP == "/" ]; then
        echo "Divide Numbers"
        DIV=0
        echo "Enter number1: "
        read N1

        echo "Enter number2: "
        read N2

        DIV=$((N1/N2))

        echo "Result: $DIV"
    elif [ $OP == "%" ]; then
        echo "Modulus Numbers"
        SUB=0
        echo "Enter number1: "
        read N1

        echo "Enter number2: "
        read N2

        MOD=$((N1%N2))

        echo "Result: $MOD"
    fi
done

exit 0

我知道这是一个小的但是无法弄清楚我在这里缺少什么。

Answer 1

将初始提示放在循环中。

代替：

echo "Input an Operation: +, -, *, /, and % (0 to stop): "
read OP

while [ $OP != "0" ]
do
    ...

做这个：

while [ $OP != "0" ]
do
    echo "Input an Operation: +, -, *, /, and % (0 to stop): "
    read OP
    ...