要求：

       内存使用空间大于80%时发送邮件报警

[root@LNMPServer ~]# vim use_mem.sh

###################################################################
# File Name: use_mem.sh
# Author: zhangweibin
# E-mail: lnhxzwb@126.com
# Created Time: Fri 26 Jan 2018 12:39:01 PM CST
#==================================================================
#!/bin/bash
ip=$(ifconfig eth0|awk '/netmask/{print $2}')
use_mem=$(free -m |awk '/Mem/{printf "%u\n", $3/$2*100}')

if [ "$use_mem" > "80" ];then
echo "主机 $ip 内存使用率已达到 $use_mem% ，请及时处理" | mail -s "内存警报" root
fi