E-mails a warning to the e-mail address when disk-usage on the main partition is over 90% ($threshold). Overwrites a log with the last runtime and usage stat. Requires SSMTP

DiskReport.sh

#! /bin/bash
CURRENT=$(df / | grep / | awk '{ print $5 }' | sed 's/%//g')
THRESHOLD=90
LOGFILE=~/Scripts/DiskReport.log

echo "Last Run: $(date "+%d%m%Y %T") : $CURRENT% Used." > $LOGFILE

if [ "$CURRENT" -gt "$THRESHOLD" ] ; then
    ssmtp -s 'Disk Space Alert' helpdesk@domain.tld << EOF
Root partition remaining free space is critically low. Used: $CURRENT%
EOF
fi