linux 用shell比较两个整数的大小

#1.判断是不是两个数
[ $# -ne 2 ] && {
echo "Usage:$0 num1 num2"
exit 1
    }   
#2.判断是否为数字
expr $1 + $2 + 999 &>/dev/null
[ $? -ne 0 ] &&{ 
echo "请输入两个整数"
exit 2
}
if [ $1 -gt $2 ]
then
    echo "$1>$2"
elif [ $1 -lt $2 ]
then
    echo "$1<$2"
else
    echo "$1=$2"
fi    
========================
read -p "please two number: " a b 
expr $a + $b + 999 &>/dev/null
if [ $? -ne 0 ] 
then
    echo "请输入两个整数"
    exit 1
else
    if [ $a -gt $b ]
    then
        echo "$a>$b"
    elif [ $a -lt $b ]
    then
        echo "$a<$b"
    else
        echo "$a=$b"
    fi  
fi