diff --git a/build.sh b/build.sh
index b1da063b..74e7f71f 100755
--- a/build.sh
+++ b/build.sh
@@ -1,28 +1,32 @@
 #!/bin/sh
 
-usage() { echo "Usage: $0 [-u | -d ]" 1>&2;echo "-u:enable update";echo "-d:disable update"; exit 1; }
+usage() {
+    printf "Usage: %s [ -u | -d ]\n" "$0" 1>&2
+    printf "  -u   enable update\n" 1>&2
+    printf "  -d   disable update\n" 1>&2
+    exit 1
+}
 
-if [  $#  =  0 ];then
-usage
+if [ $# = 0 ];then
+    usage
 fi
 
-version=`sed -n -e "s/.*<em:version>\(.*\)<\/em:version>/\1/p" install.rdf`
-while getopts  ":ud" OPTION
+version=$(sed -n -e "s/.*<em:version>\(.*\)<\/em:version>/\1/p" install.rdf)
+while getopts ":ud" OPTION
 do
     case ${OPTION} in
         u) echo "update"  
-	cat defaults/preferences/update_enable.txt > defaults/preferences/update.js
- 	zip -r exchangecalendar-v$version.xpi * -x \*.git \*.xpi \*.sh  update\*.txt
-	exit
-	;;
+	   cat defaults/preferences/update_enable.txt > defaults/preferences/update.js
+ 	   zip -r exchangecalendar-v"$version".xpi ./* -x \*.git \*.xpi \*.sh  update\*.txt
+	   exit
+	   ;;
         d) echo "no update" 
-	cat defaults/preferences/update_disable.txt > defaults/preferences/update.js
- 	zip -r exchangecalendar-v$version.xpi * -x \*.git \*.xpi \*.sh  update\*.txt
-	exit
-	;;
+	   cat defaults/preferences/update_disable.txt > defaults/preferences/update.js
+ 	   zip -r exchangecalendar-v"$version".xpi ./* -x \*.git \*.xpi \*.sh  update\*.txt
+	   exit
+	   ;;
 	*) usage ;; 
     esac
 done 
- 
-usage
 
+usage