具有动态变量名的 if 语句

Question

我创建了动态变量。

for (( c=1; c<=2; c++ ))
do  
   eval "prev$c=$number";
done

prev1,prev2

for (( c=1; c<=2; c++ ))
do  
   eval "current$c=$number";
done

current1,current2

如果我有变量

$prev1是1
$prev2是2
$current1是1
$current2​3

如何在循环内与 if 进行比较？以下是错误的，有人可以纠正语法吗？提前致谢。

for (( c=1; c<=2; c++ ))
do  
 if ((prev$i != current$i)); then
    echo "prev$i is $prev[i] and current$i is $current[i], they are different"
  fi
done

Answer 1

在bash中，您可以使用变量间接寻址

    prev=prev$c
    current=current$c

    if ((${!prev} != ${!current})); then
        echo "prev$c is ${!prev} and current$c is ${!current}, they are different"
    fi

但使用数组更安全（无需评估）：

#! /bin/bash
number=0
for (( c=1; c<=2; c++ )) ; do
    prev[c]=$number
    number=$c
    current[c]=$number

    if ((${prev[c]} != ${current[c]})); then
        echo "prev$c is ${prev[c]} and current$c is ${current[c]}, they are different"
    fi
done