diff --git a/lxc-backup.sh b/lxc-backup.sh
index bb66228..05f25c1 100755
--- a/lxc-backup.sh
+++ b/lxc-backup.sh
@@ -1,64 +1,52 @@
 #!/usr/bin/env bash
 
 main() {
+  # Set default options
+  local cmd="${CMD:-lxc}"
+  local backup_dir="${BACKUP_DIR:-$PWD}"
+  local compression="${COMPRESSION:-zstd}"
+  local vm_list
+  local retention=0
+
   while getopts ":l:d:t:x:c:h" opt; do
     case "${opt}" in
       l)
-        unset VM_FILTER
-        IFS="," read -r -a VM_FILTER <<< "$OPTARG"
-        ;;
+        IFS="," read -r -a vm_list <<< "$OPTARG";;
       d)
-        local backup_location="${OPTARG}"
-        backup_location="${backup_location%/}"
-        ;;
+        backup_dir="${OPTARG%/}";;
       t)
-        declare -g TARGET="$OPTARG"
-        ;;
+        cmd="$OPTARG";;
       x)
-        declare -g EXTENSION
-        if [[ "${OPTARG,,}" == 'none' ]]; then
-          EXTENSION=""
-        else
-          command -v "$OPTARG" >/dev/null 2>&1 || { echo "$OPTARG command not found"; exit 1; }
-          EXTENSION="${OPTARG,,}"
-        fi
-
-        declare -g COMPRESSION="$OPTARG"
-        ;;
+        compression="$OPTARG";;
       c)
-        declare -g run_cleanup=y
-        declare -g files_to_keep="${OPTARG}"
-        ;;
-      h)
-        usage
-        ;;
-      *)
-        usage
-        ;;
+        retention="${OPTARG}";;
+      h|*)
+        usage;;
     esac
   done
 
-  backup_location=${backup_location:-$PWD}
+  # Helper functions
+  lxc() { command "$cmd" "$@"; }
+  list_vms() { lxc list -c n -f csv; }
 
-  if [[ "${#VM_FILTER[*]}" -gt 0 ]]; then
-    backup_vms "$backup_location" "${VM_FILTER[@]}"
-  else
-    backup_vms "$backup_location"
+  if ((${#vm_list[@]} == 0)); then
+    mapfile -t vm_list < <(list_vms)
   fi
-}
 
-lxc() {
-	local lxc_cmd="${TARGET:-lxc}"
-	command "$lxc_cmd" "$@"
-}
+  for vm in "${vm_list[@]}"; do
+    start_backup "$vm" "$backup_dir" "$compression"
 
-list_vms() {
-	lxc list -c n -f csv
+    if (( retention > 0 )); then
+      prune_backups "$vm" "$backup_dir" "$retention"
+    fi
+  done
+
+  exit 0
 }
 
 usage() {
   cat <<EOF
-Usage: ${0##*/} [-l vm[,vm...]] [-d backup_dir] [-t lxc|incus] [-x <compression alogorithm>] [-c <keep n backups>] [-h]
+Usage: ${0##*/} [-l vm[,vm...]] [-d <backup directory>] [-t lxc|incus] [-x <compression alogorithm>] [-c <keep last n backups>] [-h]
 
 Options:
   -l  Comma-separated list of VMs to back up
@@ -72,47 +60,39 @@ EOF
   exit 1
 }
 
-backup_vms() {
-  local backup_location="$1"; shift
-  local vms=("$@")
-
-  # when no argument use list of all VMs
-  if ((${#vms[@]} == 0)); then
-    mapfile -t vms < <(list_vms)
-  fi
-
-  for vm in "${vms[@]}"; do
-    [[ -n $vm ]] || continue
-    start_backup "$vm" "$backup_location"
-  done
-}
-
 start_backup() {
   local vm=$1
-  local backup_base="$2"
-  local compression="${COMPRESSION:-none}"
-  local ext="${EXTENSION}" ; [[ -n "$ext" ]] && ext=".${ext}"
-  local destination="${backup_base}/${vm}"
+  local backup_dir="$2"
+  local compression="$3"
+  local ext=".${compression}"
+
+  if [[ "$compression" == 'none' ]]; then 
+    ext=""
+  else
+    command -v "$compression" >/dev/null 2>&1 || { echo "$compression command not found"; exit 1; }
+  fi
+
+  local vm_dir="${backup_dir}/${vm}"
 
   local backup_name
   backup_name="${vm}_$(date +"%Y-%m-%d_%H-%M-%S").tar${ext}"
 
-  [[ -d "$backup_base" ]] || { echo "${backup_base} is not a directory"; exit 1; }
-  [[ -d "$destination" ]] || mkdir "$destination"
-  [[ -f "${destination}/${backup_name}" ]] && { echo "Backup already exists"; return 2; }
-
-  lxc export "$vm" --instance-only --compression "${compression}" "${destination}/${backup_name}" || { echo "Error exporting $vm"; return 1; }
-
-  [[ -n "$run_cleanup" ]] && prune_backups "$destination"
+  [[ -d "$backup_dir" ]] || { echo "${backup_dir} is not a directory"; exit 1; }
+  [[ -d "$vm_dir" ]] || mkdir "$vm_dir" || { echo "Cannont create $vm_dir"; exit 1; }
+  [[ -f "${vm_dir}/${backup_name}" ]] && { echo "Backup already exists"; return 2; }
+  echo "starting $vm"
+  lxc export "$vm" --instance-only --compression "${compression}" "${vm_dir}/${backup_name}" || { echo "Error exporting $vm"; return 1; }
 }
 
 prune_backups() {
-  local backup_directory="$1"
-  mapfile -t backup_files < <(find "$backup_directory" -maxdepth 1 -type f -printf '%T@ %p\n' | sort -n | head -n "-${files_to_keep}" | cut -d' ' -f2-)
+  local vm="$1"
+  local backup_dir="$2"
+  local retention="$3"
+  mapfile -t backup_files < <(find "${backup_dir}/${vm}" -maxdepth 1 -type f -printf '%T@ %p\n' | sort -n | head -n "-${retention}" | cut -d' ' -f2-)
   
   if [[ ${#backup_files[@]} -gt 0 ]]; then
-    echo "Removing ${#backup_files[@]} old backup files for $vm (keeping last $files_to_keep files)"
-    printf '%s\0' "${backup_files[@]}" | xargs -0 rm -fv
+    echo "Removing ${#backup_files[@]} old backup files for $vm (keeping last $retention files)"
+    printf '%s\0' "${backup_files[@]}" | xargs -0 rm -fv > /dev/null
   else
     echo "No old backups to remove for $vm"
   fi