shell 进行浮点运算

shell 进行浮点运算，看一例 你就会了，哈哈；

#!/bin/bash
cpu=`top -n 1 | grep Cpu | awk -F: '{print $2}' | awk -F "[%,]+" '{print $1,$2,$3,$4,$5,$6,$7,$8}'`
us=`echo $cpu | awk '{print $2}'`
echo "us $us"
sy=`echo $cpu | awk '{print $5}'`
echo "sy $sy"
ni=`echo $cpu | awk '{print $8}'`
echo "ni $ni"
id=`echo $cpu | awk '{print $11}'`
echo "id $id"
a=$(echo "$us+$ni+$sy"|bc)
b=$(echo "$us+$ni+$sy+$id"|bc)
used=`echo $a $b | awk '{printf "%.2f\n",100*($1/$2)}'`
echo "     cpu ratio                    $used"