bash 变量乘法
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Variables Multiplication
提问by UraniumSnake
I'm making a script which gives the factorial for a inserted number, but i'm having some problems with the multiplication.
我正在制作一个脚本，它为插入的数字提供阶乘，但我在乘法方面遇到了一些问题。
Note: the factorial for is given by: 9!=9*8*7*6*5*4*3*2*1
注意：阶乘为： 9!=9*8*7*6*5*4*3*2*1
Here's my code:
这是我的代码：
#!/bin/bash
echo "Insert an Integer"
read input
if ! [[ "$input" =~ ^[0-9]+$ ]] ; then
exec >&2; echo "Error: You didn't enter an integer"; exit 1
fi
function factorial
{
while [ "$input" != 1 ];
do
result=$(($result * $input))
input=$(($input-1))
done
}
factorial
echo "The Factorial of " $input "is" $result
it keeps giving me errors of all kinds for diferent multiplication technics :/
它不断给我各种不同的乘法技术错误：/
Currently the Output is:
目前输出是：
joaomartinsrei@joaomartinsrei ~/área de Trabalho/Shell $ ./factorial.sh
Insert an Integer
3
./factorial.sh: line 15: * 3: syntax error: operand expected (error token is "* 3")
The factorial of 3 is
Many Thanks, Best Regards
非常感谢，最好的问候
回答by ruakh
The main problem is that you never initialize result(to 1), so this:
主要问题是您从未初始化result(to 1)，因此：
result=$(($result * $input))
is equivalent to this:
相当于：
result=$(( * $input))
which is not a valid arithmetic expression.
这不是有效的算术表达式。
