Question

我想创建一个while循环，要求用户输入yes或no，如果用户输入其他任何内容，它将一直循环直到用户输入yes或no

echo "Do you wish to save these settings?"
read response
while [ "$response" != "yes" ] | [ "$response != "no" ] 
do
   echo "Please enter yes or no only"
   echo "Do you wish to save these settings?"
   read response 
done

当我尝试输入“是”时，它仍然继续循环，但是当我输入“否”时，它退出循环

Answer 1

在外壳中，|（或管道）运算符用于使用右侧的命令过滤左侧的命令输出。

例如，下面的shell行：

seq 1 3 | tac

...将导致左侧命令产生的行...

1
2
3

...由左侧的命令过滤（它将以相反的顺序发出行）。输出将是：

3
2
1

您正在寻找对两个命令的退出状态执行布尔运算的运算符。由于您一直希望只要响应既不是yes也不是no，就可以继续循环，因此，求和运算符（&&）就是您想要的：

echo "Do you wish to save these settings?"
read response
while [ "$response" != "yes" ] && [ "$response" != "no" ] 
do
   echo "Please enter yes or no only"
   echo "Do you wish to save these settings?"
   read response 
done

如果在运行脚本的任何地方bash外壳程序始终可用，则可以通过使用[[ ... ]]而不是[ ... ]来进一步改进。除了潜在的性能优势外，使用[[的另一个优势是放宽了对严格引用的要求：

echo "Do you wish to save these settings?"
read response
while [[ $response != yes ]] && [[ $response != no ]] 
do
   echo "Please enter yes or no only"
   echo "Do you wish to save these settings?"
   read response 
done

进一步的改进来自以下知识：[[支持&&连接两个布尔表达式：

echo "Do you wish to save these settings?"
read response
while [[ $response != yes && $response != no ]] 
do
   echo "Please enter yes or no only"
   echo "Do you wish to save these settings?"
   read response 
done

Answer 2

只需while true，直到满意为止

while true
do
    echo "Do you wish to save these settings?"
    read response
    if [[ "$response" = "yes" ]] || [[ "$response" = "no" ]]
    then
        break
    fi
    echo "Please enter yes or no only"
done

如何进行2个条件的while循环并在真实条件下停止

2 个答案: