Shell：if语句

判断变量是否为空

#!/bin/sh  
a=  
# 判断中的双引号要加
if [ ! -n "$a" ]; then
	echo "IS NULL" 
else
	echo "NOT NULL"
fi

判断状态

if [ $status= "active" ];then
   fun1
elif [ $status= "standby" ];then
   fun2
else
   echo "状态异常"
fi