【参考链接】

http://stackoverflow.com/questions/35734666/floating-point-number-comparison-in-bash-script


【问题】

I tried to compare floating point number by -gt but it says that point expecting integer value. That means it can not handle floating point number . Then i tried the following code

我想用-gt比较两个浮点数大小，但屏幕却提示期望整数数值。

这就意味着-gt不能处理浮点数。接着我使用以下代码

chi_square=4
if [ "$chi_square>3.84" | bc ]
then
echo yes
else
echo no
fi

但屏幕却输出以下错误信息：

line 3: [: missing `]'
File ] is unavailable.
no

Here the no is echoed but it should be yes. I think that's because of the error it's showing. can anybody help me.

这里，执行结果本该是yes，此刻却提示no。我认为或许与提示的错误信息有关，谁能帮帮我呢？

【解决办法】

1.使用bc

要想使用bc的话请参考以下用法：

chi_square=4
if [[ $(bc -l <<< "$chi_square>3.84") -eq 1 ]]; then
   echo 'yes'
else
   echo 'no'
fi
或
if [[ `echo "$chi_square > 3.84" |bc` -eq 1 ]] ;then echo yes;else echo no ;fi

可通过bc的man手册来查看，若表达式成立则返回1。

expr1 > expr2
The result is 1 if expr1 is strictly greater than expr2.

2.使用awk

Just use awk instead

$ awk -v chi_square=4 'BEGIN{print (chi_square > 3.84 ? "yes" : "no")}'
yes

$ awk -v chi_square=3 'BEGIN{print (chi_square > 3.84 ? "yes" : "no")}'
no

或许，你并不喜欢使用三目运算，我也提供了使用shell变量来解决此问题。

$ chi_square=4
$ awk -v chi_square="$chi_square" 'BEGIN{
    if (chi_square > 3.84) {
        print "yes"
    }
    else {
        print "no"
    }
}'
yes
或
$ echo "$chi_square" |
awk '{
    if ($0 > 3.84) {
        print "yes"
    }
    else {
        print "no"
    }
}'
yes
或者
$ echo "$chi_square" | awk '{print ($0 > 3.84 ? "yes" : "no")}'
yes