check_softwareupdate_helper

#!/bin/sh
#
# (c)2019 Christian Kujau <lists@nerdbynature.de>
#
# Helper script for "check_softwareupdate.sh cron", which will expect
# a readable text file listing available package updates. Each line
# is expected to start with "Package: " but sed(1) can help with that.
#
# A cron job would look like this:
# 
# 0 */12  * * * /usr/local/sbin/check_softwareupdate_helper apk  /var/tmp/nagios_updates.txt
# 0 */12  * * * /usr/local/sbin/check_softwareupdate_helper dnf  /var/run/nrpe/nagios_updates.txt
# 0 */12  * * * /usr/local/sbin/check_softwareupdate_helper opkg /tmp/opkg_list-upgradable.txt
#
_usage() {
	echo "Usage: $(basename "$0") [apk|dnf|opkg] [state file]"
	echo "   Ex: $(basename "$0") apk /var/tmp/nagios_updates.txt"
	echo "   Ex: $(basename "$0") dnf ~nrpe/nagios_updates.txt"
	echo "   Ex: $(basename "$0") opkg /tmp/opkg_list-upgradable.txt"
	exit 1
}

# Sanity check
[ $# -eq 2 ] && STATE="$2" || _usage

# Readable STATE file?
if [ -f "${STATE}" ] && [ ! -O "${STATE}" ]; then
	echo "State file ${STATE} already in place but not owned by UID $(id -u)!"
	exit 1
else
	touch "${STATE}" && chmod a+r "${STATE}"
fi

case $1 in
	apk)
	apk update --quiet
	apk upgrade --simulate | grep Upgrading | sed 's/.*Upgrading/Package:/' > "${STATE}"
	;;

	dnf)
	dnf check-update | grep -Ev '^Last metadata|^$' | sed 's/^/Package: /'  > "${STATE}"
	;;

	opkg)
	opkg update > /dev/null
	opkg list-upgradable | awk '{print "Package:", $1}' | sort > "${STATE}"
	;;

	*)
	_usage
	;;
esac