diff --git a/git-fix-whitespace b/git-fix-whitespace
index d7a2e8c..184a2b9 100755
--- a/git-fix-whitespace
+++ b/git-fix-whitespace
@@ -1,9 +1,12 @@
 #!/bin/bash
+
+me="$(basename $0)"
+
 usage() {
-    me="$(basename $0)"
     cat << EOF
 git-fix-whitespace - Fixes the whitespace issues that 'git-diff --check'
                      complains about.
+
 Usage:
     $me --cached
     $me tree-ish tree-ish
@@ -44,17 +47,34 @@ err_files(){
     git diff $ARG1 $ARG2 --check | sed -E '/^(\+|-)/d;s/:.*//' | sort | uniq
 }
 
-PATCH=$(mktemp ${0##*/}.patch.XXXXXX)
-if [[ $# == 1 && "$1" == "--cached" ]]; then
-    ARG1=$1
-    ARG2=HEAD
-elif [[ $# == 2 ]]; then
-    ARG1=$1
-    ARG2=$2
-else
-    usage
-    exit
-fi
+case "$#" in
+    1)
+        test "$1" = "--cached" && ARG1=$1 || {
+            echo
+            echo "Inavlid arguments"
+            echo
+            echo
+            usage
+        }
+        ARG1=$1
+        ARG2=HEAD
+        ;;
+    2)
+        ARG1=$1
+        ARG2=$2
+        ;;
+    *)
+        test $# > 3 && {
+            echo
+            echo "Invalid arguments"
+            echo
+            echo
+        }
+        usage
+        ;;
+esac
+
+PATCH=$(mktemp -p $(pwd -P) ${me}.patch.XXXXXX)
 git diff $ARG1 $ARG2 > $PATCH
 FILES=$(sed '/^+++ /!d;s?^+++ b/??' $PATCH)
 echo -e "Files in index with whitespace errors:\n$(err_files 1)"