Question

我正在尝试在bash中实现连续除法算法并且我面临一个问题，即循环中的模数之一返回错误结果

我尝试了多种主要计算（（a％b）），expr和bc的模数的方法，但是都存在相同的问题

dec=$1
echo ----Dividing----
echo "dividing $dec by $2"
div=$((dec/$2))
echo "the result is $div"
rem=$((dec%$2))
res="$rem"   
echo " the remainder is $rem"
while [ $div != 0 ]
 do   
   div_old=$div 
   echo "dividing $div by $2"
   div=$((div/$2))
   echo "the result is $div"  
   rem=$(echo "$div % $2" | bc)
   echo " the remainder is $rem"
   if [ $rem != 0 ]
   then
       res="$rem$res"
   else
       res="$div_old$res"
   fi  
   echo "for now the result is $res"
 done

$ 1 = 2371和$ 2 = 5

预期结果为33441，但我的脚本返回33341

在此输出中看到

----Dividing----
dividing 2371 by 5
the result is 474
 the remainder is 1
dividing 474 by 5
the result is 94
 the remainder is 4
for now the result is 41
dividing 94 by 5
the result is 18
 the remainder is 3
for now the result is 341
dividing 18 by 5
the result is 3
 the remainder is 3
for now the result is 3341
dividing 3 by 5
the result is 0
 the remainder is 0
for now the result is 33341
33341

但是当我尝试在脚本之外执行与

相同的操作时

echo $(echo "94 % 5" | bc)

结果是4很好，为什么循环的内部/外部之间会有这样的区别？

Answer 1

div=$((div/$2))
...
rem=$(echo "$div % $2" | bc)
 ...

您要划分下一个div，而不是旧的/当前的/前一个。您的意思是，划分旧的div，获取新的div，然后将相同的old_div与rem一起使用：

div_old=$div
echo "dividing $div_old by $2"
div=$((div_old / $2))
echo "the result is $div"
rem=$((div_old % $2))

请注意，if [ $rem != 0 ]正在进行字符串比较，它不等于数字。要将数字与[或test进行比较，请使用-ne：

if [ $rem -ne 0 ]

或者仅使用bash算术扩展：

if ((rem != 0))

与while [ $div != 0 ]

While循环中Modulo的结果为false，但在循环外计算时不为假

1 个答案: