Shell 脚本 - 添加内存功能答案

【问题标题】：Shell Script - Adding memory functionalityShell 脚本 - 添加内存功能
【发布时间】：2021-05-24 06:12:59
【问题描述】：

#!/bin/bash

while true
do
     if [[ $# -eq 0 ]] ; then
         echo Enter operand1 value:
         read operand1
 
         # Offer choices
         echo 1. Addition
         echo 2. Subtraction
         echo 3. Multiplication
         echo 4. Division
         echo 5. Exit
 
         echo Enter your choice:
         read choice

         if [[ $choice != 1 || 2 || 3 || 4 || 5 ]] ; then
             echo Sorry $choice is not a valid operator - please try again 
             echo Enter your choice:
             read choice
         else 
             Continue 
         fi
 
         echo Enter operand2 value:
         read operand2
 
         # get operands and start computing based on the user's choice
         if [[ $choice -eq 1 ]] ; then
             echo ----------------------------------------
             echo Addition of $operand1 and $operand2 is $((operand1+operand2))
             echo ----------------------------------------
             echo
         elif [[ $choice -eq 2 ]] ; then
             echo ----------------------------------------
             echo Subtraction of $operand1 and $operand2 is $((operand1-operand2))
             echo ----------------------------------------
             echo
         elif [[ $choice -eq 3 ]] ; then
             echo ----------------------------------------
             echo Multiplication of $operand1 and $operand2 is $((operand1*operand2))
             echo ----------------------------------------
             echo
         elif [[ $choice -eq 4 && operand2 -eq 0 ]] ; then
             echo Can not divide by 0 please try again 
             echo Please enter operand2
             read operand2
             echo ----------------------------------------
             echo Division of $operand1 and $operand2 is $((operand1/operand2))
             echo ----------------------------------------
             echo    
          elif [[ $choice -eq 4 && operand2 -ne 0 ]] ; then
             echo ----------------------------------------
             echo Division of $operand1 and $operand2 is $((operand1/operand2))
             echo ----------------------------------------
             echo    
         elif [[ $choice -eq 5 ]] ; then
             exit    
         else
             echo ----------------------------------------
             echo Invalid choice.. Please try again
             echo ----------------------------------------
             echo
         fi        
   else
             echo ----------------------------------------
             echo You either passed too many parameters or too less
             echo than the optimum requirement.
             echo
             echo This program accepts a maximum of 2 arguments or no
             echo argument at all in order to run successfully.
             echo ----------------------------------------
   fi
done

我希望在上面的代码中添加功能，以便每个后续操作都将使用以前的结果，提示用户输入下一个运算符和操作数，这样用户就不必再次输入第一个操作数，而且很简单将其存储在内存中。我似乎想不出任何方法来做到这一点 - 有什么建议吗？

【问题讨论】：

问：你想一遍又一遍地使用“operand1”的相同值……还是想在后续的第一个操作数中使用result操作？在任何一种情况下：只需使用 shell 变量。 将结果分配给变量 ...而不是仅仅打印它。 Here 是检查 Bash 变量是否已分配的方法。
问题中的代码应该是minimal reproducible example -- 演示特定问题的最短的可能。为什么有五个选项和一堆echos？除此之外，尚不清楚为什么您在跨迭代存储值时遇到问题 - 您设置的变量保留在原地，那么当您尝试时出现的具体问题是什么？
顺便说一句，[[ $choice != 1 || 2 || 3 || 4 || 5 ]] 始终为真，因为在检查[[ $choice != 1 ]]（可能为真或假）后，它检查[[ 2 ]]，它始终为真（因为它等同于@987654329 @，而2 不是空字符串）。
感谢@CharlesDuffy 指出这一点，我现在明白了。你能推荐一种格式化的方法吗？我一直在尝试输入一行，向用户显示他们输入了一个不正确的操作符，这是唯一一个真正与我的脚本一起工作的操作符。任何朝着正确方向推动的帮助都会非常有帮助
问题的上述方面与Compare string to multiple correct values重复。

标签： bash shell unix

【解决方案1】：

您应该将结果存储在这样的变量中：

result=$((operand1+operand2))

然后你的第一个if 语句可以检查这个变量是否有值，如果有，跳过read 并使用它。

if [[ $result == "" ]]; then
    echo Enter operand1 value:
    read operand1
else
    operand1=$result
    echo "Operand 1 is: $result"
    echo ""
fi
...

这是您的代码的工作版本：

#!/bin/bash

while true
do
     if [[ $# -eq 0 ]] ; then
        if [[ $result == "" ]]; then # check if $result is empty
            echo Enter operand1 value: 
            read operand1
        else
            operand1=$result # if not empty then assign its value to $operand1
            echo "Operand 1 is: $result"
            echo ""
        fi
 
         # Offer choices
         echo 1. Addition
         echo 2. Subtraction
         echo 3. Multiplication
         echo 4. Division
         echo 5. Exit
 
         echo Enter your choice:
         read choice

         if [[ $choice != 1 && $choice != 2 && $choice != 3 && $choice != 4 && $choice != 5 ]] ; then
             echo Sorry $choice is not a valid operator - please try again 
             echo Enter your choice:
             read choice
         fi
 
         echo Enter operand2 value:
         read operand2
 
         # get operands and start computing based on the user's choice
         if [[ $choice -eq 1 ]] ; then
             result=$((operand1+operand2)) # store result
             echo ----------------------------------------
             echo Addition of $operand1 and $operand2 is $((operand1+operand2))
             echo ----------------------------------------
             echo
         elif [[ $choice -eq 2 ]] ; then
             result=$((operand1-operand2)) # store result
             echo ----------------------------------------
             echo Subtraction of $operand1 and $operand2 is $((operand1-operand2))
             echo ----------------------------------------
             echo
         elif [[ $choice -eq 3 ]] ; then
             result=$((operand1*operand2)) # store result
             echo ----------------------------------------
             echo Multiplication of $operand1 and $operand2 is $((operand1*operand2))
             echo ----------------------------------------
             echo
         elif [[ $choice -eq 4 && operand2 -eq 0 ]] ; then
             echo Can not divide by 0 please try again 
             echo Please enter operand2
             read operand2
             echo ----------------------------------------
             echo Division of $operand1 and $operand2 is $((operand1/operand2))
             echo ----------------------------------------
             echo    
             result=$((operand1/operand2)) # store result
          elif [[ $choice -eq 4 && operand2 -ne 0 ]] ; then
             result=$((operand1/operand2)) # store result
             echo ----------------------------------------
             echo Division of $operand1 and $operand2 is $((operand1/operand2))
             echo ----------------------------------------
             echo    
         elif [[ $choice -eq 5 ]] ; then
             exit    
         else
             echo ----------------------------------------
             echo Invalid choice.. Please try again
             echo ----------------------------------------
             echo
         fi        
   else
             echo ----------------------------------------
             echo You either passed too many parameters or too less
             echo than the optimum requirement.
             echo
             echo This program accepts a maximum of 2 arguments or no
             echo argument at all in order to run successfully.
             echo ----------------------------------------
   fi
done

【讨论】：

感谢您的输入，我是否必须为每个操作添加一个结果变量以在循环之前存储？
@LukeMcCutcheon 您可以在每种操作类型中向用户回显答案之后或之前存储该值。
@LukeMcCutcheon 我添加了一个使用 cmets 标记更改的工作示例