base-files: gracefully handle empty variables in preinit (#11155)

SVN-Revision: 31030

target/linux/rdc/base-files/lib/preinit/05_set_ether_mac_rdc

 #!/bin/sh
-# Copyright (C) 2009 OpenWrt.org
+# Copyright (C) 2009-2012 OpenWrt.org
 
 . /lib/functions/boot.sh
 
@@ -13,7 +13,7 @@ r6040_module() {
 
 set_ether_mac() {
 	kernel=$(grep firmware /proc/mtd | awk -F: '{print $1}')
-	[ -n $kernel ] && hdr=$(dd if=/dev/$kernel count=4 bs=1 2> /dev/null)
+	[ -n "$kernel" ] && hdr=$(dd if=/dev/$kernel count=4 bs=1 2> /dev/null)
 	[ "$hdr" = "CSYS" ] && config=$(find_mtd_part config)
 	if [ -n "$config" ]; then
 		mac0=$(hexdump -n 6 -e '6/1 ":%X"' -s 24583 $config | cut -c2-)
@@ -21,13 +21,13 @@ set_ether_mac() {
 		mac1=$(hexdump -n 6 -e '6/1 ":%X"' -s 24589 $config | cut -c2-)
 		[ "$mac1" = "FF:FF:FF:FF:FF:FF" -o "$mac0" = "0:0:0:0:0:0" ] && unset mac1
 	fi
-	if [ -n $mac0 ]; then
+	if [ -n "$mac0" ]; then
 		logger -t kernel -p user.info "r6040: Setting MAC for eth0 to $mac0"
-		ifconfig eth0 hw ether $mac0
+		ifconfig eth0 hw ether "$mac0"
 	fi
-	if [ -n $mac1 ]; then
+	if [ -n "$mac1" ]; then
 		logger -t kernel -p user.info "r6040: Setting MAC for eth1 to $mac1"
-		ifconfig eth1 hw ether $mac1
+		ifconfig eth1 hw ether "$mac1"
 	fi
 }