diff --git a/phototrie/batchrename.py b/phototrie/batchrename.py
index 3f70d0e..605b78e 100644
--- a/phototrie/batchrename.py
+++ b/phototrie/batchrename.py
@@ -40,7 +40,7 @@ def cli():
 
     pattern = re.compile(args.pattern)
 
-    for filename in sys.argv[3:]:
+    for filename in args.files:
         base = os.path.basename(filename)
         dirn = os.path.dirname(filename)
         new_base = pattern.sub(args.replacement, base)
diff --git a/phototrie/datename.py b/phototrie/datename.py
index cded8ed..140860b 100644
--- a/phototrie/datename.py
+++ b/phototrie/datename.py
@@ -20,9 +20,13 @@ def get_new_name(filename, date_matches):
 
     while True:
         if suffix == 0:
-            target = f"{dirn}/{year}-{month}-{date}_{hour}:{second}:{minute}{extension}"
+            target_base = f"{year}-{month}-{date}_{hour}:{second}:{minute}{extension}"
         else:
-            target = f"{dirn}/{year}-{month}-{date}_{hour}:{second}:{minute}_{suffix}{extension}"
+            target_base = (
+                f"{year}-{month}-{date}_{hour}:{second}:{minute}_{suffix}{extension}"
+            )
+
+        target = os.path.join(dirn, target_base)
 
         if not os.path.exists(target):
             return target
@@ -74,7 +78,9 @@ def cli():
             found_raw = unextended + ".CR2"
         else:
             unextended_basename = os.path.basename(unextended)
-            try_next = os.path.dirname(filename) + "/CR2/" + unextended_basename
+            try_next = os.path.join(
+                os.path.dirname(filename), "CR2", unextended_basename + ".CR2"
+            )
             if os.path.exists(try_next):
                 found_raw = try_next
 
diff --git a/phototrie/phototrie.py b/phototrie/phototrie.py
index e8439c2..859b0f8 100644
--- a/phototrie/phototrie.py
+++ b/phototrie/phototrie.py
@@ -28,7 +28,7 @@ def prepare_processable(search_in: str):
                 found_raw = unextended + ".CR2"
             else:
                 unextended_basename = os.path.basename(unextended)
-                try_next = os.path.dirname(file) + "/CR2/" + unextended_basename
+                try_next = os.path.join(os.path.dirname(file), "CR2", unextended_basename + ".CR2")
                 if os.path.exists(try_next):
                     found_raw = try_next
 
@@ -86,6 +86,9 @@ def cli():
     print("<phototrie.py> [file extension to process e.g. CR2 or jpg.")
     print("keybinds: B 'bad', 'G' good, 'P' pristine")
 
+    if len(sys.argv) < 2:
+        sys.exit(1)
+
     to_process, tmp_dir = prepare_processable(".")
 
     dirs = "./bad", "./good", "./pristine"