This script comes from a blog study with learning A Ming:
The most basic of company monitoring is to monitor the use of disks, otherwise it will lead to business accidents.
General monitoring requirements are as follows: every minute to scan the status of the disk.
When disk space usage or inode usage is higher than 90%, an alarm is required.
And all subdirectories of partitions with statistical utilization rate of more than 90% are arranged in order of size, and the names of the first three directories are sent to the mailbox.
First untreated, 30 minutes later in one.

#!/bin/bash
#Purpose: Monitor disk usage.
#Author: Caron maktini
#Date: 18 October 2018
#Version: v0.1
#Exist script name in variable l-name
l_name=`echo $0 | awk -F '/' 'print $NF'`
#Define the recipient's mailbox
mail_user=admin@admin.com

#Define a space utilization function for checking disks
chk_sp()
{
    df -m | sed '1d' | awk -F '% | +' '$5>90 {print $7,$5}'>/tmp/chk_sp.log
    n=`wc -l /tmp/chk_sp.log | awk 'print $1'`
    if [ $n -gt 0 ]
    then 
      tag=1
      for d in `awk '{print $1}' /tmp/chk_sp.log`
      do 
           find $d -type d | sed '1d' | xargs du -sm | sort -nr | head -3
      done >/tmp/most_sp.txt
   fi
               
}

#Define check inode usage function

chk_in()
{
  df -i | sed `1d` | awk -F '% | +' '$5>90 {print $7,$5}'>/tmp/chk_in.log
    n=`wc -l /tmp/chk_in.log | awk '{print $1}'`
    if [ $n -gt 0 ]
    then 
        tag=2
    fi
 }

#Define alarm function

m_mail(){
    log=$1
    t_s=`date +%s`
    t_s2=`data -d "1 hours ago" +%s`
    if [ ! -f /tmp/$log ]
    then
        #Create a $log file
        touch /tmp/$log
        #Added a permission, only allowed additional content, not allowed to change or delete
        chattr +a /tmp/$log
        #The first alarm can be written directly to the timestamp one hour ago
        echo $t_s2 >> /tmp/$log
     fi
    #whether#Whether the log file has just been created requires looking at the timestamp of the last line
    t_s2=`tail -l /tmp/$log | awk '{print $1}'`
    # Take out the timestamp of the last line and the last alarm and write it to the current timestamp immediately
    echo $t_s >>/tmp/$log
    #Take the difference of two timestamps
    v=$[ $t_s-$t_s2 ]
    #If the difference exceeds 100, send the mail immediately.
    if [ $v -gt 1800 ]
    then
      #Send an email, where $2 is the second function of the mail function, and here is a file
      python  mail.py $mail_user "Disk usage over 90%"
      #Define the temporary file of the technicians and write it to 0
      echo "0" > /tmp/$log.count
     else
      #If the technicians temporary file does not exist, you need to create and write 0
      if [ ! -f /tmp/$log.count }
      then
         echo "0" > /tmp/$log.count 

      fi

      nu=`cat /tmp/$log.count`
      #For every alarm in 30 minutes, add 1 to the calculator
      nu2=$[ $nu+1 ]
      echo $nu2>/tmp/$log.count
      #When the number of alarms exceeds 30, it is necessary to send oil again.
      if [ $nu2 -gt 30 ]
      then 
          python mail.py $mail_user "Disk utilization rate 90%It lasted 30 minutes." "`cat $2`" 2>/dev/null
          #After the second alarm, start the calculator from zero again
          echo "0" > /tmp/$log.count
      fi
 fi 
}
#If the number of processes is greater than 0, the last script has not been executed.
if [ $p_n -gt 0 ]
then
    exit

fi
 

chk_sp
chk_in

if [ $tag == 1 ]
then
    m_mail chk_sp /tmp/most_sp.txt
elif [ $tag == 2 ]
then
    m_mail chk_in /tmp/chk_in.log
fi