Improve shell flags

ur/fortinet.vpn.sh

@@ -13,16 +13,28 @@
 # 2023-01-24
 # }}}
 # Flags {{{
-## Exit on error
+## Exit on error {{{
 set -o errexit
-
+## }}}
+## Exit on unset var {{{
+### Use "${VARNAME-}" to test a var that may not have been set
+set -o nounset
+## }}}
+## Pipeline command is treated as failed {{{
+### Not available in POSIX sh − https://github.com/koalaman/shellcheck/wiki/SC3040
+#set -o pipefail
+## }}}
+## Help with debugging {{{
+### Call the script by prefixing it with "TRACE=1 ./script.sh"
+if [ "${TRACE-0}" -eq 1 ]; then set -o xtrace; fi
+## }}}
 # }}}
 # Vars {{{
 PROGNAME=$(basename "${0}"); readonly PROGNAME
-PROGDIR=$(readlink -m $(dirname "${0}")); readonly PROGDIR
+PROGDIR=$(readlink --canonicalize-missing $(dirname "${0}")); readonly PROGDIR
 ARGS="${*}"; readonly ARGS
 readonly NBARGS="${#}"
-[ -z "${DEBUG}" ] && DEBUG=1
+[ -z "${DEBUG-}" ] && DEBUG=1
 ## Export DEBUG for sub-script
 export DEBUG
 
@@ -72,7 +84,7 @@ OPTIONS :
         Define VPN user name to use.
         Default : ${VPN_USER_DEFAULT}
 
-For a first connection, try to start `forticlient gui` first to configure EMS
+For a first connection, try to start \`forticlient gui\` first to configure EMS
 and to check profile name.
 
 HELP
@@ -96,7 +108,7 @@ error_message() {                                               # {{{
 	local_error_code="${2}"
 
 	## Print message
-	printf '%b\n' "ERROR − ${PROGNAME} : ${RED}${local_error_message}${RESET}"
+	printf '%b\n' "ERROR − ${PROGNAME} : ${RED}${local_error_message}${RESET}" >&2
 
 	unset local_error_message
 
@@ -106,19 +118,19 @@ error_message() {                                               # {{{
 define_vars() {                                                 # {{{
 
 	## If request_status wasn't defined (argument) {{{
-	if [ -z "${request_status}" ]; then
+	if [ -z "${request_status-}" ]; then
 		## Use default value
 		readonly request_status="${REQUEST_STATUS_DEFAULT}"
 	fi
 	## }}}
 	## If vpn_profile_name wasn't defined (argument) {{{
-	if [ -z "${vpn_profile_name}" ]; then
+	if [ -z "${vpn_profile_name-}" ]; then
 		## Use default value
 		readonly vpn_profile_name="${VPN_PROFILE_NAME_DEFAULT}"
 	fi
 	## }}}
 	## If vpn_user wasn't defined (argument) {{{
-	if [ -z "${vpn_user}" ]; then
+	if [ -z "${vpn_user-}" ]; then
 		## Use default value
 		readonly vpn_user="${VPN_USER_DEFAULT}"
 	fi
@@ -200,7 +212,6 @@ main() {                                                        # {{{
 	## If the VPN must be started {{{
 	if [ "${request_status}" = "start" ]; then
 		debug_message "-- Connect VPN BEGIN"
-		#systemd_forticlient_status=$(sudo systemctl status forticlient.service | grep --word-regexp "Active:" | sed 's/Active: \(.*\)/\1/' || error_message "Error while requesting current VPN status." 22)
 		### If forticlient.service unit is not started {{{
 		systemd_forticlient_status=$(systemctl show forticlient.service | grep "^ActiveStat" | sed 's/.*=\(.*\)/\1/' || error_message "Error while requesting forticlient.service unit status." 21)
 		if [ "${systemd_forticlient_status}" = "failed" ]; then
@@ -221,7 +232,7 @@ main() {                                                        # {{{
 
 		if [ "${forticlient_status}" = "Not Running" ]; then
 			### If script was started from a launcher {{{
-			if [ -n "${DISPLAY}" ] && [ "${TERM}" = "linux" ]; then
+			if [ -n "${DISPLAY-}" ] && [ "${TERM}" = "linux" ]; then
 				### Try to launch a new TERM_EMULATOR to ask the password
 				"${TERM_EMULATOR}" -e forticlient vpn connect "${vpn_profile_name}" --password --user="${vpn_user}" \
 					|| error_message "Error when connecting to VPN profile (${vpn_profile_name})." 24
@@ -250,9 +261,6 @@ main() {                                                        # {{{
 }
 # }}}
 
-true > /tmp/vpn.env
-env | sort >> /tmp/vpn.env
-
 # Manage arguments                                                # {{{
 # This code can't be in a function due to argument management
 
@@ -260,19 +268,20 @@ if [ ! "${NBARGS}" -eq "0" ]; then
 
 	manage_arg="0"
 
+	## If the first argument ask for help (h|help|-h|-help|-*h|-*help)
+	if printf -- '%s' "${1-}" | grep --quiet --extended-regexp -- "^-*h(elp)?$"; then
+		usage
+		exit 0
+	fi
+
 	# Parse all argument one by one
-	while printf -- '%s' "${1}" | grep -q -- "."; do
+	while printf -- '%s' "${1-}" | grep --quiet -- "."; do
 
 	case "${1}" in
 		-d|--debug )                          ## debug
 			DEBUG=0
 			debug_message "--- Manage argument BEGIN"
 			;;
-		-h|--help )                           ## help
-			usage
-			## Exit after help informations
-			exit 0
-			;;
 		--start|start )                       ## Define request_status to start
 			## Define var
 			readonly request_status="start"