ffgraz-ddhcpd-batman-adv: fix shellcheck issues

ffgraz-ddhcpd-batman-adv/files/usr/sbin/ddhcpd-gateway-update

@@ -1,4 +1,5 @@
-#!/bin/sh
+#!/bin/busybox sh
+# shellcheck shell=dash
 
 CACHE_TTL=600
 CACHE_FILE=/tmp/ddhcp_gw_cache
@@ -7,20 +8,22 @@ GW_UPDATE_TRIES=5
 
 
 verbose() {
-	[ -n "$VERBOSE" ] && ( >&2 echo $@ )
+	[ -n "$VERBOSE" ] && ( >&2 echo "$@" )
 }
 
 mac_to_ipv6_ll() {
-	IFS=':'; set $1; unset IFS
+	IFS=':'; set "$1"; unset IFS
 	echo "fe80::$(printf %02x $((0x$1 ^ 2)))$2:${3}ff:fe$4:$5$6"
 }
 
 get_gw_ipv4_address() {
 	local gwmac="$1"
-	local gwid="`echo "$gwmac" | tr -d ':'`"
-	gluon-neighbour-info -p 1001 -d "`mac_to_ipv6_ll "$gwmac"`" -i br-client -r gateway | \
-		while read resp; do
-			local node_id="`echo "$resp" | jsonfilter -e '$.node_id'`"
+	local gwid
+	gwid="$(echo "$gwmac" | tr -d ':')"
+	gluon-neighbour-info -p 1001 -d "$(mac_to_ipv6_ll "$gwmac")" -i br-client -r gateway | \
+		while read -r resp; do
+			local node_id
+			node_id="$(echo "$resp" | jsonfilter -e '$.node_id')"
 			if [ "$node_id" = "$gwid" ]; then
 				echo "$resp" | jsonfilter -e '$.address.ipv4'
 			fi
@@ -40,49 +43,55 @@ update_gateway() {
 	/usr/sbin/ddhcpdctl -o "6:4:$1"
 }
 
-gwmac="`batctl gwl | sed 's/([[:space:]]*[0-9]\+)//g' | sed 's/[[:space:]]\+/ /g' | egrep '(^\*)|(=>)' | cut -d' ' -f2`"
-[ -z "$gwmac" ] && {
+gwmac="$(batctl gwl | sed 's/([[:space:]]*[0-9]\+)//g' | sed 's/[[:space:]]\+/ /g' | grep -E '(^\*)|(=>)' | cut -d' ' -f2)"
+if [ -z "$gwmac" ]; then
 	verbose Failed to determine mac address of current gateway
 	gateway_lost
 	exit 1
-}
+fi
 
 verbose Got gateway mac address: "$gwmac"
 
-[ -f "$CACHE_FILE" ] && {
+# disable checks for unknown variables (SC2154) because they are loaded from an unknown files (SC1090)
+# shellcheck disable=SC1090,SC2154
+if [ -f "$CACHE_FILE" ]; then
 	verbose Retrieving cache
-	source "$CACHE_FILE"
-	now="`date +'%s'`"
-	if echo "$last_update_time" | egrep -q '^[0-9]+$' && \
-	    echo "$last_gwaddr" | egrep -q '^(([0-9]){1,3}\.){3}[0-9]{1,3}$'; then
-		verbose Gateway mac address cache found, age $(($now - $last_update_time))
-		if [ "$gwmac" = "$last_gwmac" ] && \
-		    [ $(($now - $last_update_time)) -lt "$CACHE_TTL" ]; then
+	. "$CACHE_FILE"
+	now="$(date +'%s')"
+	if echo "$last_update_time" | grep -E -q '^[0-9]+$' && \
+		echo "$last_gwaddr" | grep -E -q '^(([0-9]){1,3}\.){3}[0-9]{1,3}$'
+	then
+		verbose "Gateway mac address cache found, age $((now - last_update_time))"
+		if [ "$gwmac" = "$last_gwmac" ] && [ $((now - last_update_time)) -lt "$CACHE_TTL" ]
+		then
 			verbose Cache is up to date
 			update_gateway "$last_gwaddr"
 			exit 0
 		fi
 	fi
 	verbose Updating cache
-}
+fi
 
-for _ in `seq "$GW_UPDATE_TRIES"`; do
-	gwaddr="`get_gw_ipv4_address "$gwmac"`"
+for _ in $(seq "$GW_UPDATE_TRIES"); do
+	gwaddr="$(get_gw_ipv4_address "$gwmac")"
 	[ -n "$gwaddr" ] && break
 done
-[ -z "$gwaddr" ] && [ ! "$gwmac" == "$last_gwmac" ] && {
+
+if [ -z "$gwaddr" ] && [ ! "$gwmac" = "$last_gwmac" ]; then
 	verbose Failed to retrieve new gateway IPv4 address
 	gateway_lost
 	exit 2
-}
-[ ! -z "$gwaddr" ] && {
+fi
+
+if [ -z "$gwaddr" ]; then
+	verbose "Information gathering failed, done nothing"
+	exit 0
+fi
+
 verbose Got gateway IPv4 address: "$gwaddr"
 
 echo "last_gwmac=\"$gwmac\"" > "$CACHE_FILE"
 echo "last_gwaddr=\"$gwaddr\"" >> "$CACHE_FILE"
-echo "last_update_time=`date +'%s'`" >> "$CACHE_FILE"
+echo "last_update_time=$(date +'%s')" >> "$CACHE_FILE"
 
 update_gateway "$gwaddr"
-} || {
-  verbose Information gathering failed, done nothing
-}