Shell Script to check memory usage. If memory usage beyond 70%, should send mail.

memory_usage.sh

# !/bin/bash

# To find memory usage in MB
used=$(free -mt | grep Total | awk '{print $3}')
total=$(free -mt | grep Total | awk '{print $2}')
echo $used "MB used out of " $total "MB"

# TO calculate memory usage percentage
usage_percent= expr " $used * 100 / $total" | bc 

# Check if memory usage beyond 70% or not, if yes then send mail
if [[ $usage_percent -gt  70 ]];
then
	echo "Oops! $HOSTNAME memory usage beyond 70%. Please take a note." \
             | mail -s "Memory usage beyond 70%" root@localhost
        echo "Mail sent successfully.!!"
        

else
        echo "Memory usage less than 70%"
fi

# Memory_Usage script should run every hour, every month between monday to friday

#write out current crontab
crontab -l > mycron

#echo new cron into cron file
echo "59 * * * 1-5 ./memory_usage.sh" >> mycron

#install new cron file after every hour
crontab mycron
rm mycron