Shell编程（四）Shell变量

1. 自定义变量

1.1 定义变量

#!/usr/bin/bash
ip=115.239.210.27

if ping -c1 $ip &>/dev/null ;then    # &>/dev/null: output of ping $ip is null
    echo "$ip is up."
else
    echo "$ip is down."
fi

1.2 输入变量

#!/usr/bin/bash
read ip

ping -c1 $ip &>/dev/null
if [ $? -eq 0 ]; then
    echo "$ip is up."
else
    echo "$ip is down."
fi

1.3 位置变量（$1, $2.....）

#!/bin/bash
                       
ping -c1 $1 &>/dev/null
if [ $? -eq 0 ]; then
    echo "$1 is up."   
else
    echo "$1 is down." 
fi

2. 环境变量

2.1 export

echo "ip1 is $ip1"
echo "ip2 is $ip2"

(ip2 是环境变量)