四、变量的赋值方法

#!/bin/bash
a=$1
b=$2
echo "a-b=$(($a-$b))"
echo "a+b=$(($a+$b))"
echo "a*b=$(($a*$b))"
echo "a/b=$(($a/$b))"
echo "a**b=$(($a**$b))"
echo "a%b=$(($a%$b))"

#!/bin/bash
cat <<EOF
  1.install lamp
  2.install lnmp
  3.exit
EOF
read -p "请选择一个序号（必须是数字）：" num
#1.判断是否为整数
expr 2 + $num &>/dev/null
if [ $? -ne 0 ]
then
    echo "Usage:$0 {1|2|3}"
    exit 1
fi

#2.判断执行处理
if [ $num -eq 1 ]
then
    echo "install lamp..."
elif [ $num -eq 2 ]
then
    echo "install lnmp..."
elif [ $num -eq 3 ]
then
    echo "bye."
    exit 
else
    echo "Usage:$0 {1|2|3}"
    exit 1
fi