非常实用的清理buffcache小脚本

#!/bin/bash
#可用内存小于20%清理buffcache
Mem=`free -m|awk 'NR==2'|awk '{print $2}'`
used=`free -m|awk 'NR==2'|awk '{print $3}'`
free=`free -m|awk 'NR==2'|awk '{print $4}'`
note=`echo $Mem \* 0.2|bc|awk -F '.' '{print $1}'`
date=`date +"%Y-%m-%d %H:%M:%S"`
echo '-----------------' >> /tmp/mem.log
echo $date >> /tmp/mem.log
if [ $free -le $note ];then
    echo use:free $used:$free >> /tmp/mem.log
  sync && echo 1 > /proc/sys/vm/drop_caches  
    sync && echo 2 > /proc/sys/vm/drop_caches  
    sync && echo 3 > /proc/sys/vm/drop_caches
  new_used=`free -m|awk 'NR==2'|awk '{print $3}'`
  new_free=`free -m|awk 'NR==2'|awk '{print $4}'`
  echo success >> /tmp/mem.log
  echo use:free $new_used:$new_free >> /tmp/mem.log
else
  echo No need to clean up >> /tmp/mem.log
fi