Add an error message if number of arguments is incorrect

update_latest.sh

@@ -3,6 +3,11 @@ set -e
 
 version="$1"
 
+if [ -z "$version" ]; then
+	echo "Usage: $0 version"
+	exit 1
+fi
+
 ln -sf ../downloads/$version latest/directory
 for f in $(ls "downloads/$version/"); do \
     ln -sf "../downloads/$version/$f" latest/$(echo $f | sed -e "s@-$version@@")