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代码有什么问题吗？

tag-icon • tag-icon shell-script
代码有什么问题吗？ 
#!/bin/bash
for ((i=1 ;i<=3;i++))
do
echo "Enter gallon used(gal):"
read gal
echo "Enter Miles Obtained(mil):"
read mil
mileage=`echo $mil / $gal |bc`
echo "scale=4; $mileage " | bc
c=`echo $c + $mileage | bc`
echo "$c + $mileage = $c"
echo
done

答案1

你的蓄能器是吗c？首先将其设置为零，这样第 10 行就不会出现语法错误。

您会得到一个整数结果，因为第 9 行中没有任何操作。将第 8 行和第 9 行合并为

mileage=$(echo "scale=4; $mil / $gal" | bc)

然后mileage就会得到一个小数结果。

您没有做任何有用的事情$c，并且在循环后无法打印它。

答案2

#!/usr/bin/env bash

# Above, get the path to BASH from the environment.
# Below, you could just set the total mileage here.
total_mileage=0

# Below, start from zero and count up for the three loops.
for ((i=0; i<3; i++)); do
    # Below, use `-n` to prevent the new line.
    # It's ok to use descriptive variable names.
    # echo -n "Enter gallons used: "
    # Below, quote variables.
    # read "gallons"

    # Using the suggestion for `read` from @roaima :
    read -p "Enter gallons used  : " "gallons"

    # Use a regular expression (regex). Here, a number with optional decimal:
    while [[ ! $gallons =~ ^[+-]?[0-9]+\.?[0-9]*$ ]]; do
        echo "Please enter a number or [CTRL]+[C] to exit."
        read -p "Enter gallons used  : " "gallons"
    done

    # echo -n "Enter miles obtained: "
    # read "miles"

    # Using the suggestion for `read` from @roaima :
    read -p "Enter miles obtained: " "miles"
    while [[ ! $miles =~ ^[+-]?[0-9]+\.?[0-9]*$ ]]; do
        echo "Please enter a number or [CTRL]+[C] to exit."
        read -p "Enter miles obtained: " "miles"
    done

    # Below, backticks are antiquated.
    mileage=$(echo "scale=4; ($miles) / ($gallons)" | bc)
    echo "Mileage: $mileage"

    total_mileage=$(echo "scale=4; $total_mileage + $mileage" | bc)

done

average_mileage=$(echo "scale=4; ($total_mileage) / ($i)" | bc)
echo "Average mileage is $average_mileage"

也可以看看这些：

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