Merge pull request #41 from diplozoon/patch-2

Fix a bug when there is no optional argument

Author: mkaz

termgraph/termgraph.py

@@ -122,6 +122,11 @@ def init_args():
         action='store_true',
         help='Display version and exit'
     )
+    if len(sys.argv) == 1:
+        if sys.stdin.isatty():
+            parser.print_usage()
+            sys.exit(2)
+
     args = vars(parser.parse_args())
 
     if args['custom_tick'] != '':