scripts/cluster/apt.check.update.sh

#!/bin/sh

# This script will check if any APT upgrade is available and
# will prepare the host in order to apply upgrade with another script
#   1. Create a temp file
#   2. Disable SGE queue

# This script can be call by a cronjob (eg. weekly)
# Another script should try to apply upgrades also with cron (eg. hourly)

# Vars {{{
readonly PROGNAME=$(basename "${0}")
readonly PROGDIR=$(readlink -m $(dirname "${0}"))
readonly ARGS="${*}"
readonly NBARGS="${#}"
[ -z "${DEBUG}" ] && readonly DEBUG=1
## Export DEBUG for sub-script
export DEBUG

readonly APT_TMP_FILE="/tmp/.apt.upgrade"

## Colors
readonly PURPLE='\033[1;35m'
readonly RED='\033[0;31m'
readonly RESET='\033[0m'
readonly COLOR_DEBUG="${PURPLE}"
# }}}

manage_args() {                                                 # {{{

	case "${NBARGS}" in
		0 ) ## Nothing to do
			;;
		* )
			printf '%b\n' "${RED}Don't expect any arguments.${RESET}"
			printf '%b\n' "---"
			usage
			exit 1
			;;
	esac

}
# }}}
usage() {                                                       # {{{

	cat <<- EOF
usage: $PROGNAME

Verify if any APT package upgrade is available and
try to prepare the host by :
	* Disabling SGE queue

EXAMPLES :
    - Verify upgrade and prepare the current host
        ${PROGNAME}
	EOF

}
# }}}
debug_message() {                                               # {{{

	local_message="${1}"

	## Print message if DEBUG is enable (=0)
	[ "${DEBUG}" -eq "0" ] && printf '\e[1;35m%-6b\e[m\n' "DEBUG − ${PROGNAME} : ${local_message}"

}
# }}}
is_apt_upgrade_absent() {                                       # {{{

	## Count the number of upgradable packages and substract 1 for the header
	local_apt_upgrade_number="$(apt list --upgradable \
		| wc -l \
		| awk '{print $1-1}')"

	case "${local_apt_upgrade_number}" in
		0 ) ## No available upgrade
			return_apt_upgrade_absent="0"
			;;
		* ) ## Upgrade seems available
			return_apt_upgrade_absent="1"
			;;
esac

	## Simple debug message to valid current variable
	debug_message "is_apt_upgrade_absent − \
APT upgrade available for this system: ${RED}${local_apt_upgrade_number:=/dev/null}${COLOR_DEBUG}."

	return "${return_apt_upgrade_absent}"

}
# }}}
is_apt_upgrade_present() {                                      # {{{

	## Count the number of upgradable packages and substract 1 for the header
	local_apt_upgrade_number="$(apt list --upgradable \
		| wc -l \
		| awk '{print $1-1}')"

	case "${local_apt_upgrade_number}" in
		0 ) ## No available upgrade
			return_apt_upgrade_present="1"
			;;
		* ) ## Upgrade seems available
			return_apt_upgrade_present="0"
			;;
esac

	## Simple debug message to valid current variable
	debug_message "is_apt_upgrade_present − \
APT upgrade available for this system: ${RED}${local_apt_upgrade_number:=/dev/null}${COLOR_DEBUG}."

	return "${return_apt_upgrade_present}"

}
# }}}
main() {                                                        # {{{

	manage_args "${ARGS}"

	sge_disable_host_queue_script="${PROGDIR}/sge.disable.host.queue.sh"

	## If NO APT package upgrade is available
	### Ensure to remove any temp file related to APT upgrades
	### Exit
	is_apt_upgrade_absent \
		&& rm -f -- "${APT_TMP_FILE}" \
		&& exit 0

	## If APT package upgrade is available
	### Create a temp file
	### Disable SGE queue
	is_apt_upgrade_present \
		&& touch "${APT_TMP_FILE}" && echo "APT upgrade is available." >> "${APT_TMP_FILE}" \
		&& sh "${sge_disable_host_queue_script}" \
		&& exit 0

}
# }}}

main

exit 255