bash - 为什么异或两个大二进制数会给出十进制输出？

Question

我正在尝试对两个大的二进制值进行异或。然而，

echo ${hashArray[1]}
echo ${hashArray[2]}
echo $((${hashArray[1]} ^ ${hashArray[2]}))

给出：

10100100000111101011100001101110000110000100001000000111001001100010110000010010111101100110111001111100010010000000010101110111

00001110110000010110101101011011100101101000011100011101001101101010000100110001001110101101111100010001111010100011010000000100

4018181242766406943

为什么echo $((${hashArray[1]} ^ ${hashArray[2]}))输出一个十进制数？它不应该是另一个大的二进制值吗？

Answer 1

bash确实支持二进制数字，但是您的数字太大并且会被截断。要么按照mana的建议进行操作，要么拆分字符串，或者使用可以处理任意精度的库，例如 perl 的 Math::BigInt 浮现在脑海中：

异或.pl

use Math::BigInt;

$x = Math::BigInt->new("0b" . $ARGV[0]); 
$y = Math::BigInt->new("0b" . $ARGV[1]);

print $x->bxor($y)->as_bin;

为方便起见，将数字分配给变量：

x=10100100000111101011100001101110000110000100001000000111001001100010110000010010111101100110111001111100010010000000010101110111
y=00001110110000010110101101011011100101101000011100011101001101101010000100110001001110101101111100010001111010100011010000000100

运行：

perl xor.pl $x $y

输出：

0b10101010110111111101001100110101100011101100010100011010000100001000110100100011110011001011000101101101101000100011000101110011

Answer 2

像这样“按位”进行操作：

#!/bin/bash

a="101"
b="011"

out=""
for ((i=0; i < ${#a}; i++ )); do
   out=${out}$((${a:$i:1} ^ ${b:$i:1}))
done

echo ${a} ^ ${b} = $out

输出：

101 ^ 011 = 110

编辑：输入需要具有相同的长度！

Answer 3

用bc按位做，首先得到文件 logic.bc ：

wget http://phodd.net/gnu-bc/code/logic.bc

测试异或（）

x=10100100000111101011100001101110000110000100001000000111001001100010110000010010111101100110111001111100010010000000010101110111
y=00001110110000010110101101011011100101101000011100011101001101101010000100110001001110101101111100010001111010100011010000000100

echo "ibase=2;obase=2;xor($x,$y)" | bc -l logic.bc

结果：

10101010110111111101001100110101100011101100010100011010000100001000110100100011110011001011000101101101101000100011000101110011