fix hostname hash on linux

.zshrc

@@ -77,17 +77,20 @@ case `uname` in
   Darwin)
     PR_HOST_COLOR=$PR_CYAN
     MD5_COMMAND=md5
+    MD5_COMMAND_OPTS=""
     ;;
   *)
     PR_HOST_COLOR=$PR_GREEN
-    MD5_COMMAND=md5sum
+    MD5_COMMAND="md5sum"
+    MD5_COMMAND_OPTS="--tag"
     ;;
 esac
 
 PR_HOST_COLOR=$PR_NO_COLOUR
 if [ -x "$(command -v $MD5_COMMAND)" ]; then
-  str=`echo -n "${HOST} ${HOSTNAME}" | $MD5_COMMAND`
+  str=`echo -n "${HOST} ${HOSTNAME}" | $MD5_COMMAND $MD5_COMMAND_OPTS`
   last="${str: -1}"
+  echo
   case $last in
     "1"|"6"|"b"|"0")
       PR_HOST_COLOR=$PR_GREEN