您可以通过-l选项使用bc (L字母)

RESULT=$(echo "$IMG_WIDTH/$IMG2_WIDTH" | bc -l)

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.

如果你找到了你喜欢的变体，你也可以把它包装到一个函数中。

这里我将一些bashism包装到div函数中:

一个衬套:

function div { local _d=${3:-2}; local _n=0000000000; _n=${_n:0:$_d}; local _r=$(($1$_n/$2)); _r=${_r:0:-$_d}.${_r: -$_d}; echo $_r;}

或多行:

function div {
  local _d=${3:-2}
  local _n=0000000000
  _n=${_n:0:$_d}
  local _r=$(($1$_n/$2))
  _r=${_r:0:-$_d}.${_r: -$_d}
  echo $_r
}

现在你得到了这个函数

div <dividend> <divisor> [<precision=2>]

然后像这样使用它

> div 1 2
.50

> div 273 123 5
2.21951

> x=$(div 22 7)
> echo $x
3.14

更新 我添加了一个小脚本，为您提供了bash的基本浮点数操作:

用法:

> add 1.2 3.45
4.65
> sub 1000 .007
999.993
> mul 1.1 7.07
7.7770
> div 10 3
3.
> div 10 3.000
3.333

这里是脚本:

#!/bin/bash
__op() {
        local z=00000000000000000000000000000000
        local a1=${1%.*}
        local x1=${1//./}
        local n1=$((${#x1}-${#a1}))
        local a2=${2%.*}
        local x2=${2//./}
        local n2=$((${#x2}-${#a2}))
        local n=$n1
        if (($n1 < $n2)); then
                local n=$n2
                x1=$x1${z:0:$(($n2-$n1))}
        fi
        if (($n1 > $n2)); then
                x2=$x2${z:0:$(($n1-$n2))}
        fi
        if [ "$3" == "/" ]; then
                x1=$x1${z:0:$n}
        fi
        local r=$(($x1"$3"$x2))
        local l=$((${#r}-$n))
        if [ "$3" == "*" ]; then
                l=$(($l-$n))
        fi
        echo ${r:0:$l}.${r:$l}
}
add() { __op $1 $2 + ;}
sub() { __op $1 $2 - ;}
mul() { __op $1 $2 "*" ;}
div() { __op $1 $2 / ;}

您可以通过-l选项使用bc (L字母)

RESULT=$(echo "$IMG_WIDTH/$IMG2_WIDTH" | bc -l)

你不能。Bash只处理整数;您必须委托给bc之类的工具。