Linux Shell Script to Monitor Space Usage and Send Email
Linux shell script to check /var logs space and send email if used space reach 80%. Also print space usage of each directory inside /var. Useful to find out which folder use most of space under /var. This script really helps system administrator to monitor their servers space usage. Based on the requirement , administrators can change the directoires they want to monitor.

#!/bin/bash
LIMIT='80'
#Here we declare variable LIMIT with max of used spave
DIR='/var'
#Here we declare variable DIR with name of directory
#Here we declare variable MAILTO with email address
SUBJECT="$DIR disk usage"
#Here we declare variable SUBJECT with subject of email
MAILX='mailx'
#Here we declare variable MAILX with mailx command that will send email
which $MAILX > /dev/null 2>&1
#Here we check if mailx command exist
if ! [ $? -eq 0 ]
#We check exit status of previous command if exit status not 0 this mean that mailx is not installed on system
then
          echo "Please install $MAILX"
#Here we warn user that mailx not installed
          exit 1
#Here we will exit from script
fi
cd $DIR
#To check real used size, we need to navigate to folder
USED=`df . | awk '{print $5}' | sed -ne 2p | cut -d"%" -f1`
#This line will get used space of partition where we currently, this will use df command, and get used space in %, and after cut % from value.
if [ $USED -gt $LIMIT ]
#If used space is bigger than LIMIT
then

      du -sh ${DIR}/* | $MAILX -s "$SUBJECT" "$MAILTO"