linux腳本判斷當前的linux版本是6還是7

#!/bin/sh

version="release 7."
release=$(cat /etc/redhat-release)
echo $release
result=$(echo $release | grep "${version}")
if [[ "$result" != "" ]]
    then
        echo "當前linux版本是7"
else
    echo "當前linux版本是6"
fi