bash 四舍五入浮点数bash
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Rounding up float point numbers bash
提问by Quill
Ok, so I'm trying to round up an input of 17.92857, so that it gets an input of 17.929in bash.
好的，所以我正在尝试对 的输入进行四舍五入17.92857，以便它17.929在 bash 中获得输入。
My code so far is:
到目前为止我的代码是：
read input
echo "scale = 3; $input" | bc -l
However, when I use this, it doesn't round up, it returns 17.928.
但是，当我使用它时，它不会四舍五入，而是返回17.928.
Does anyone know any solutions to this?
有谁知道任何解决方案？
回答by Tim Zimmermann
In case inputcontains a number, there is no need for an external command like bc. You can just use printf:
如果input包含数字，则不需要像bc. 你可以只使用printf：
printf "%.3f\n" "$input"
Edit:In case the input is a formula, you should however use bcas in one of the following commands:
编辑：如果输入是公式，则应使用bc以下命令之一：
printf "%.3f\n" $(bc -l <<< "$input")
printf "%.3f\n" $(echo "$input" | bc -l)
回答by Zane Hooper
To extend Tim's answer, you can write a shell helper function round ${FLOAT} ${PRECISION}for this:
要扩展 Tim 的答案，您可以为此编写一个 shell 辅助函数round ${FLOAT} ${PRECISION}：
#!/usr/bin/env bash
round() {
printf "%.f" ""
}
PI=3.14159
round ${PI} 0
echo
round ${PI} 1
echo
round ${PI} 2
echo
round ${PI} 3
echo
round ${PI} 4
echo
round ${PI} 5
echo
round ${PI} 6
echo
# Outputs:
3
3.1
3.14
3.142
3.1416
3.14159
3.141590
# To store in a variable:
ROUND_PI=$(round ${PI} 3)
echo ${ROUND_PI}
# Outputs:
3.142
回答by Ludovic Feltz
A little trick is to add 0.0005to your input, this way you will have your number round up correctly.
一个小技巧是添加0.0005到您的输入中，这样您就可以正确地对数字进行四舍五入。
回答by reyb
if you're receiving the round-off error with the number 17.928 try this:
read y
v=echo "scale = 3; $y" |bc -lif [ $v == 17.928 ] ; then
echo "17.929"
else
echo $v
fi
如果您收到数字为 17.928 的舍入错误，请尝试以下操作： read y v= echo "scale = 3; $y" |bc -lif [ $v == 17.928 ] ; 然后回声“17.929”否则回声 $v fi
