Warn on nearly full memory

memwarn.bash

#!/bin/bash
# see https://askubuntu.com/questions/276234/need-application-script-alerting-when-system-memory-is-running-out/346779#346779
# add crontab -e the following:
# * *  *   *   *     DISPLAY=:0.0 /path/to/memwarn.bash

#Minimum available memory limit, MB
if [[ -n "$1" ]]; then
	THRESHOLD="$1"
else
	THRESHOLD=400
fi

free_output="$(free -m)"

free_free () {
	awk '/^Mem:/{print $4}'
}

free_buffers_cache () {
	awk '/^Mem:/{print $6}'
}

free_available () {
	awk '/^Mem:/{print $7}'
}

free_="$(free_free <<< "$free_output")"
buffcache="$(free_buffers_cache <<< "$free_output")"
available="$((free_ + buffcache))"
message="$free_output"

if [[ $available -lt $THRESHOLD ]]; then
	notify-send "Memory is running out!" "$message"
	paplay /usr/share/sounds/freedesktop/stereo/alarm-clock-elapsed.oga
fi