如何在 bash 中打印用户输入的平方根？
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How do i print square root of user input in bash?
提问by Zero-1729
I have recently discovered 'bc' in bash, and i have been trying to use it to print out the square root of a user input. The program i wrote below runs successfully, but it only prints out '0' and not the square root of the user input.
我最近在 bash 中发现了“bc”，我一直在尝试用它来打印用户输入的平方根。我在下面编写的程序运行成功，但它只打印出“0”而不是用户输入的平方根。
Here is the code i wrote:
这是我写的代码：
#!/data/data/com.termux/files/usr/bin/bash
echo "input value below"
read VAR
echo "square root of $VAR is..."
echo $((a))
a=$(bc <<< "scale=0; sqrt(($VAR))")
What is the problem with my code? What am i missing?
我的代码有什么问题？我错过了什么？
回答by heemayl
Your bccommand and the use of command substitution is correct, the problem is you have provided the echo $aearlier, when it was unset. Do:
您的bc命令和命令替换的使用是正确的，问题是您提供了echo $a较早的时间，但未设置。做：
a=$(bc <<< "scale=0; sqrt($VAR)")
echo "$a"
Also while expanding variables, you should use the usual notation for variable expansion which is $varor ${var}. I have also removed a pair of redundant ()from sqrt().
此外，在扩展变量时，您应该使用变量扩展的常用符号，即$var或${var}。我还()从sqrt().
回答by scientist_7
Using awkis also possible. For instance, the following example shows 30 decimals of the square root of 98:
awk也可以使用。例如，以下示例显示 98 的平方根的 30 位小数：
awk "BEGIN {printf \"%.30f\n\", sqrt(98)}"
The command above will output 9.899494936611665352188538236078, which you can then store into the avariable.
上面的命令将输出9.899494936611665352188538236078，然后您可以将其存储到a变量中。
回答by arenaq
Given that you have a number in variable varand you want square root of that variable. You can also use awk:
鉴于您在变量中有一个数字var并且您想要该变量的平方根。您还可以使用 awk：
a=$(awk -v x=$var 'BEGIN{print sqrt(x)}')
or
或者
a=$(echo "$var" | awk '{print sqrt()}')
