I am new to shell scripting and want to implement a script on my server which will automatically send email alerts if the disk usage goes over 90% and second email alert when it goes over 95%. My filesystem is abc:/xyz/abc and the mount point is /pqr.I have tried this:ADMIN=someone@def.com ALERT=90 df -H | grep -vE 'abc:/xyz/pqr | tmpfs |cdrom' | awk '{ print $5   $1 }' | while read output; do   usep=$(echo $output | awk '{ print $1}' | cut -d'%' -f1 )   partition=$(echo $output | awk '{ print $2 }' )     if [ $usep -ge $ALERT ]; then       mail -s Alert: Almost out of disk space $usep $ADMIN     fi   doneBut I am getting an error which saysline 7: [: Use: integer expression expected 
Shell script to send an alert mail if disk usage exceeds 90%
shell script;text processing;disk usage