diff --git a/.vscode/launch.json b/.vscode/launch.json
index 91dbc3b..e6a44c1 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -13,6 +13,7 @@
                 "${workspaceFolder}/tests/resources",
                 "${workspaceFolder}/output.csv",
                 "-r",
+                "-n",
                 "-p",
                 "group_num:group(\\d)-\\w-\\d+\\.txt",
                 "group(\\d)-(?P<sect>\\w)-(?P<patid>\\d+)\\.txt",
diff --git a/csvbyname/cli.py b/csvbyname/cli.py
index 9d7c9cb..c994731 100644
--- a/csvbyname/cli.py
+++ b/csvbyname/cli.py
@@ -63,6 +63,7 @@ def main():
         "Alternatively, use named REGEX groups.",
         nargs="+",
         type=str,
+        required=True
     )
     argparser.add_argument(
         "-n",
diff --git a/csvbyname/generate.py b/csvbyname/generate.py
index 6be5eb9..b830447 100644
--- a/csvbyname/generate.py
+++ b/csvbyname/generate.py
@@ -72,20 +72,24 @@ def collect_files(
 
 
 def write_collected_to_csv(
-    output_path: str, collected: dict[str, dict[str, str]], property_keys: Iterable[str]
+    output_path: str,
+    collected: dict[str, dict[str, str]],
+    property_keys: Iterable[str],
+    output_basename: bool,
 ):
     with open(output_path, "w") as output_fd:
         s_property_keys = sorted(property_keys)
-        header = ["path", *s_property_keys]
+        header = ["path"]
+        if output_basename:
+            header.append("basename")
+        header.extend(s_property_keys)
         writer = csv.writer(output_fd)
         writer.writerow(header)
         for full_path, properties in collected.items():
-            writer.writerow(
-                [
-                    full_path,
-                    *(
-                        properties[k] if k in properties else "N/A"
-                        for k in s_property_keys
-                    ),
-                ]
+            row = [full_path]
+            if output_basename:
+                row.append(os.path.basename(full_path))
+            row.extend(
+                (properties[k] if k in properties else "N/A" for k in s_property_keys)
             )
+            writer.writerow(row)