Added diskwatch script.

files/check_disk_usage.sh

+#!/bin/bash
+
+WARNINGS=$(df -l --output=source,fstype,pcent,target | tail --lines=+2 | while read source fstype usage mountpoint
+do
+    # Only filesystems that originate from some kind of device
+    if [[ "$source" != /* ]]
+    then
+	continue
+    fi
+
+    # Remove trailing percentage sign.
+    usage=${usage%%%}
+
+    # Warn if usage is above 90%
+    if [[ ${usage} -gt 89 ]]
+    then
+	echo "${source} (mounted on ${mountpoint}) is ${usage}% full"
+    fi
+done)
+
+if [[ "$WARNINGS" != "" ]]
+then
+    echo "WARNINGS"
+
+    (
+	echo -n "From: noreply@"
+	cat /etc/hostname
+	for r in $WARNING_RECIPIENTS
+	do
+	    echo "To: ${r}"
+	done
+	echo "Subject: Disk usage warning"
+	echo
+	echo "The following disks are almost full:"
+	echo "$WARNINGS"
+    ) | sendmail -t
+fi