Send an alert email if FS is 75% used in bash

df -h |sed s/%//g | awk '{if($5 > 75) print $6,$5}' | column -t | mail -s "df status alert" -r user@example.com  sender@example.com

Another method:

df -h |sed s/%//g | awk '{print $6,$5}'|while read fs usage; do if [[ $usage -ge 75 ]]; then echo "Usage is high of $fs to $usage"; fi; done > tmp_file
cat tmp_file | mail -s "df status alert" -r user@example.com  sender@example.com && rm -rf tmp_file