Script to check if APT upgrade is available

And prepare the host (by disabling SGE queue) in order to apply upgrades
asap.

cluster/check.apt.update.sh

@@ -0,0 +1,137 @@
+#!/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. 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 "${DEBUG}" ] && readonly DEBUG=1
+## Export DEBUG for sub-script
+export DEBUG
+
+## Colors
+readonly PURPLE='\033[1;35m'
+readonly RED='\033[0;31m'
+readonly RESET='\033[0m'
+readonly COLOR_DEBUG="${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 $1-1}')"
+	local_apt_upgrade_number="5"
+
+	case "${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 $1-1}')"
+	local_apt_upgrade_number="5"
+
+	case "${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 "${ARGS}"
+
+	disable_host_queue_script="${PROGDIR}/disable.host.queue.sh"
+
+	## If NO APT package upgrade is available
+	### Exit
+	is_apt_upgrade_absent \
+		&& exit 0
+
+	## If APT package upgrade is available
+	### Disable SGE queue
+	is_apt_upgrade_present \
+		&& sh "${disable_host_queue_script}"
+
+}
+# }}}
+
+main
+
+exit 0