diff --git a/directory_discrepancy.py b/directory_discrepancy.py
index c6cb312..7881cb7 100644
--- a/directory_discrepancy.py
+++ b/directory_discrepancy.py
@@ -1,20 +1,63 @@
+'''
+directory_discrepancy
+=====================
+
+This program compares two directory and shows which files exist in each
+directory that do not exist in the other.
+
+> directory_discrepancy dir1 dir2
+
+flags:
+--recurse:
+    Also check subdirectories.
+'''
 import os
+import argparse
 import sys
 
-dir1 = sys.argv[1]
-dir2 = sys.argv[2]
+from voussoirkit import betterhelp
+from voussoirkit import pathclass
+from voussoirkit import operatornotify
+from voussoirkit import spinal
+from voussoirkit import vlogging
 
-files1 = set(os.listdir(dir1))
-files2 = set(os.listdir(dir2))
+log = vlogging.getLogger(__name__, 'directory_discrepancy')
 
-print(f'In "{dir1}" but not in "{dir2}":')
-print('=============================')
-for discrepancy in sorted(files1.difference(files2)):
-    print(discrepancy)
+def helper(root, recurse):
+    root = pathclass.Path(root)
+    walk = spinal.walk(root, recurse=recurse, yield_directories=True, yield_files=True)
+    for path in walk:
+        relative = path.relative_to(root)
+        yield relative
 
-print()
+def directory_discrepancy_argparse(args):
+    files1 = set(helper(args.dir1, recurse=args.recurse))
+    files2 = set(helper(args.dir2, recurse=args.recurse))
 
-print(f'In "{dir2}" but not in "{dir1}":')
-print('=============================')
-for discrepancy in sorted(files2.difference(files1)):
-    print(discrepancy)
+    print(f'In "{args.dir1}" but not in "{args.dir2}":')
+    print('=============================')
+    for discrepancy in sorted(files1.difference(files2)):
+        print(discrepancy)
+
+    print()
+
+    print(f'In "{args.dir2}" but not in "{args.dir1}":')
+    print('=============================')
+    for discrepancy in sorted(files2.difference(files1)):
+        print(discrepancy)
+
+
+def main(argv):
+    argv = vlogging.set_level_by_argv(log, argv)
+
+    parser = argparse.ArgumentParser(description=__doc__)
+
+    parser.add_argument('dir1')
+    parser.add_argument('dir2')
+    parser.add_argument('--recurse', action='store_true')
+    parser.set_defaults(func=directory_discrepancy_argparse)
+
+    return betterhelp.single_main(argv, parser, __doc__)
+
+if __name__ == '__main__':
+    raise SystemExit(main(sys.argv[1:]))