diff --git a/bin/qemush b/bin/qemush
index 637f631..41c00cd 100755
--- a/bin/qemush
+++ b/bin/qemush
@@ -193,23 +193,17 @@ public_spice() {
         socat TCP-LISTEN:"${port},reuseaddr,fork" UNIX-CLIENT:"$(pathof spice)"
 }
 
-function_exists() {
-    declare -F \
-        | cut -d \  -f 3- \
-        | grep '^public_' \
-        | sed 's/^public_//' \
-        | grep -q "^${1}\$"
-}
+case "$1" in
+    "")
+        public_running
+        ;;
+    running|ls|add|edit|start|attach|rm|diskls|diskadd|diskrm|shell|do|spice|help)
+        function=$1
+        shift
 
-# Defauts to `active` if no function is supplied; else checks for a public
-# function named after the argument; else fails
-if [ -z "$1" ]; then
-    public_running
-elif function_exists "$1"; then
-    function=$1
-    shift
-
-    "public_${function}" "$@"
-else
-    error_usage
-fi
+        "public_${function}" "$@"
+        ;;
+    *)
+        error_usage
+        ;;
+esac