虽然在Bash中不能使用浮点除法，但可以使用定点除法。你所要做的就是把整数乘以10的次方，然后把整数部分除掉，用取模运算得到小数部分。根据需要舍入。

#!/bin/bash

n=$1
d=$2

# because of rounding this should be 10^{i+1}
# where i is the number of decimal digits wanted
i=4
P=$((10**(i+1)))
Pn=$(($P / 10))
# here we 'fix' the decimal place, divide and round tward zero
t=$(($n * $P / $d + ($n < 0 ? -5 : 5)))
# then we print the number by dividing off the interger part and
# using the modulo operator (after removing the rounding digit) to get the factional part.
printf "%d.%0${i}d\n" $(($t / $P)) $(((t < 0 ? -t : t) / 10 % $Pn))

There are scenarios in wich you cannot use bc becouse it might simply not be present, like in some cut down versions of busybox or embedded systems. In any case limiting outer dependencies is always a good thing to do so you can always add zeroes to the number being divided by (numerator), that is the same as multiplying by a power of 10 (you should choose a power of 10 according to the precision you need), that will make the division output an integer number. Once you have that integer treat it as a string and position the decimal point (moving it from right to left) a number of times equal to the power of ten you multiplied the numerator by. This is a simple way of obtaining float results by using only integer numbers.

现在是尝试zsh的最佳时机，它是一个(几乎)bash超集，具有许多其他不错的特性，包括浮点数学。下面是你的例子在zsh中的样子:

% IMG_WIDTH=1080
% IMG2_WIDTH=640
% result=$((IMG_WIDTH*1.0/IMG2_WIDTH))
% echo $result
1.6875

这篇文章可能会帮助你:bash -值得切换到zsh随意使用?

正如其他人指出的那样，bash没有内置的浮点运算符。

您可以在bash中实现浮点数，甚至不使用bc和awk之类的计算器程序，或者任何与此相关的外部程序。

我在我的项目shellmath中正是这样做的，分三个基本步骤:

把数字分成整数部分和小数部分 使用内置的整数运算符分别处理各个部分，同时注意位值和进位 重新组合结果

作为一个挑逗，我添加了一个演示脚本，使用以x=0为中心的泰勒级数计算e。

如果您有时间，请查看一下。欢迎您的反馈!

如何在bash中进行浮点计算:

不同于在bc命令中使用"here strings"(<<<)，这是我最喜欢的bc浮点示例，来自bc手册页的示例部分(参见man bc手册页)。

在我们开始之前，知道pi的方程是:pi = 4*atan(1)。下面的A()是atan()的BC数学函数。

This is how to store the result of a floating point calculation into a bash variable--in this case into a variable called pi. Note that scale=10 sets the number of decimal digits of precision to 10 in this case. Any decimal digits after this place are truncated. pi=$(echo "scale=10; 4*a(1)" | bc -l) Now, to have a single line of code that also prints out the value of this variable, simply add the echo command to the end as a follow-up command, as follows. Note the truncation at 10 decimal places, as commanded: pi=$(echo "scale=10; 4*a(1)" | bc -l); echo $pi 3.1415926532 Finally, let's throw in some rounding. Here we will use the printf function to round to 4 decimal places. Note that the 3.14159... rounds now to 3.1416. Since we are rounding, we no longer need to use scale=10 to truncate to 10 decimal places, so we'll just remove that part. Here's the end solution: pi=$(printf %.4f $(echo "4*a(1)" | bc -l)); echo $pi 3.1416

下面是上述技术的另一个非常棒的应用程序和演示:测量和打印运行时。

(参见我的另一个答案)。

注意，dt_min从0.01666666666…0.017:

start=$SECONDS; sleep 1; end=$SECONDS; dt_sec=$(( end - start )); dt_min=$(printf %.3f $(echo "$dt_sec/60" | bc -l)); echo "dt_sec = $dt_sec; dt_min = $dt_min"
dt_sec = 1; dt_min = 0.017

相关:

(我的回答)https://unix.stackexchange.com/questions/52313/how-to-get-execution-time-of-a-script-effectively/547849#547849 [我的问题]三个左尖括号(' <<< ')在bash中是什么意思? https://unix.stackexchange.com/questions/80362/what-does-mean/80368#80368 https://askubuntu.com/questions/179898/how-to-round-decimals-using-bc-in-bash/574474#574474

你不能。Bash只处理整数;您必须委托给bc之类的工具。