diff --git a/bench.sh b/bench.sh
index c6e7de3..bce9595 100755
--- a/bench.sh
+++ b/bench.sh
@@ -1,18 +1,22 @@
 #! /bin/bash
 
+tmp=$(mktemp -d /tmp/globbench.XXXXXX)
+echo "temp dir is $tmp";
+
 bench() {
-    if [[ -z $2 ]]; then
-    	$2 = ".*"
+	local exp=".*"
+    if [[ ! -z $2 ]]; then
+    	$exp = $2
     fi
-    filename="/tmp/$1.bench"
+    filename="$tmp/$1.bench"
     if test -e "${filename}";
     then
         echo "Already exists ${filename}"
     else
         backup=`git rev-parse --abbrev-ref HEAD`
-        git checkout $1
+        git checkout "$1"
         echo -n "Creating ${filename}... "
-        go test ./... -run=NONE -bench=$2 > "${filename}" -benchmem
+        go test ./... -run=NONE -bench="$exp" > "${filename}" -benchmem
         echo "OK"
         git checkout ${backup}
         sleep 5
@@ -26,4 +30,4 @@ current=`git rev-parse --abbrev-ref HEAD`
 bench ${to} $2
 bench ${current} $2
 
-benchcmp $3 "/tmp/${to}.bench" "/tmp/${current}.bench"
+benchcmp $3 "$tmp/${to}.bench" "$tmp/${current}.bench"