diff --git a/zhconv.py b/zhconv.py
index 9f9bd9b..c494249 100644
--- a/zhconv.py
+++ b/zhconv.py
@@ -30,7 +30,7 @@ def main():
 
     if os.path.isfile(input_arg):
         target_dir = os.path.dirname(input_arg)
-        target_files = [input_arg]
+        target_files = [os.path.basename(input_arg)]
     elif os.path.isdir(input_arg):
         target_dir = input_arg
         target_files = None
@@ -38,21 +38,21 @@ def main():
         print(f"Error: Path '{input_arg}' does not exist.")
         return
 
+    os.chdir(target_dir)
+
     if target_files is None:
-        target_files = glob.glob(os.path.join(target_dir, '*'))
+        target_files = glob.glob('*')
 
     converted_count = 0
-    for file_path in target_files:
-        if not os.path.isfile(file_path):
+    for filename in target_files:
+        if not os.path.isfile(filename):
             continue
-        filename = os.path.basename(file_path)
         new_filename = convert_filename(filename, cc)
         if new_filename:
-            new_path = os.path.join(target_dir, new_filename)
-            if os.path.exists(new_path):
+            if os.path.exists(new_filename):
                 print(f"Skipped (already exists): {new_filename}")
             else:
-                os.rename(file_path, new_path)
+                os.rename(filename, new_filename)
                 print(f"Converted: {filename} -> {new_filename}")
                 converted_count += 1