disk_usage

#!/bin/bash

# parse the arguments
OPTIONS=$(getopt -o hc --long help,check -n 'disk_usage' -- "$@")
if [ $? != 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi
eval set -- "$OPTIONS"

DEPENDENCIES=(
	notify-send
	df
)
[ -z "$THRESHOLD" ] && THRESHOLD=90

check_dependencies () {
	for package in ${DEPENDENCIES[@]}; do
		if [ ! $(which $package) ]; then
			echo "All of '$(echo ${DEPENDENCIES[@]})' are needed to run $0"
			exit 1
		fi
	done
}

check_root_partition_usage () {
	local disk_usage=$1

	if [ "$disk_usage" -gt "$THRESHOLD" ]; then
		notify-send "Root partition almost full" "root '/' partition is used at ${DISK_USAGE}! \n You should clear caches 'sudo pacman -Scc' for example" --urgency critical
	fi
}

usage () {
	 #
	 # the usage function.
	 #
	 echo "Usage: disk_usage [-hc]"
	 echo "Type -h or --help for the full help."
	 exit 0
}


help () {
	 #
	 # the help function.
	 #
	 echo "disk_usage:"
	 echo "     a script to check the root partition usage and throw appropriate notifications."
	 echo "     dependencies are automatically checked"
	 echo ""
	 echo '     *TESTED on MANJARO*'
	 echo "     run \`sudo systemctl enable cronie\` to activate the \`cron\` daemon if not already done, then"
	 echo "     add \`* * * * * DISPLAY=:0 DBUS_SESSION_BUS_ADDRESS=<address> /path/to/disk_usage --check\`"
	 echo "     to the \`cron\` table with \`crontab -e\` and restart the \`cron\` daemon with"
	 echo "     \`sudo systemctl restart cronie\`. The address can be found with \`echo \$DBUS_SESSION_BUS_ADDRESS\`."
	 echo ""
	 echo "Usage:"
	 echo "     disk_usage [-hc]"
	 echo ""
	 echo "Switches:"
	 echo "     -h/--help             shows this help."
	 echo "     -c/--check            check the root partition usage and throw a notification if critical."
	 echo ""
	 echo "Environment variables:"
	 echo "     THRESHOLD             the partition usage threshold to trigger the notification"
	 echo ""
	 echo "Dependencies:"
	 echo "     notify-send"
	 exit 0
}


main () {
	#
	# TODO.
	#

	check_dependencies
	while [[ $# -gt 0 ]]; do
		case "$1" in
			-h | --help )   help ;;
			-c | --check )  ACTION="check"; shift 1 ;;
			-- ) shift; break ;;
			* ) break ;;
		esac
	done

	DISK_USAGE=$(df / --output=pcent | grep --only-matching --extended-regexp '[0-9]{2,3}')

	# an action is required
	[ -z "$ACTION" ] && usage
	case "$ACTION" in
		check ) check_root_partition_usage "$DISK_USAGE" ;;
		* ) echo "an error occured (got unexpected '$ACTION')"; exit 1 ;;
	esac
}


main "$@"