diff --git a/calc_md5.sh b/calc_md5.sh
index 8089180..01ce5e6 100755
--- a/calc_md5.sh
+++ b/calc_md5.sh
@@ -1,12 +1,17 @@
 #!/bin/bash
 
-cd /mnt/export
+folder="/mnt/export/transport"
+md5="md5.txt"
+
+## prepare
+cat "${md5}" > "${md5}.bak"
 md5_tmp=`mktemp`
+md5_add="${md5}.add"
 
 #sort & del dublicates
-sed -i '/^$/d' md5.txt
-cat md5.txt | sort -k 2 | uniq > $md5_tmp
-cat $md5_tmp > md5.txt
+sed -i '/^$/d' "$md5"
+cat "$md5" | sort -k 2 | uniq > "$md5_tmp"
+cat "$md5_tmp" > "$md5"
 
 cat $md5_tmp | while read line; do
   #get md5
@@ -21,25 +26,28 @@ cat $md5_tmp | while read line; do
     echo  > /dev/null
   else
     echo "rm $line"
-    sed -i "/$md5/d" md5.txt
+    sed -i "/$md5/d" "$md5"
   fi
 
 done
 
 #search for new files
-find /mnt/export/transport -type f | grep -v "/.Trash-" | sort | while read line; do
+find "$folder" -type f | grep -v "/.Trash-" | sort | while read line; do
   #save fiel path
-  result=$(grep "$line" md5.txt); [ -z "$result" ] && {
+  result=$(grep "$line" "$md5"); [ -z "$result" ] && {
     #wenn kein eintrag in liste...
     echo "new $line"
-    md5sum "$line" >> md5.txt_add
+    md5sum "$line" >> "$md5_add"
   }
 done
-[ -f md5.txt_add ] && {
-  cat md5.txt_add >> md5.txt
-  rm md5.txt_add
+[ -f "$md5_add" ] && {
+  cat "$md5_add" >> "$md5"
+  rm "$md5_add"
 }
 
 #sort & del dublicates
-cat md5.txt | sort -k 2 | uniq > $md5_tmp
-rm md5.txt && mv $md5_tmp md5.txt
+cat "$md5" | sort -k 2 | uniq > $md5_tmp
+rm "$md5" && mv $md5_tmp "$md5"
+
+## diff
+diff "${md5}" "${md5}.bak"