1 files changed, 5 insertions, 1 deletions

diff --git a/scripts/visualize.py b/scripts/visualize.py
index 5685d1a..2899b43 100755
--- a/scripts/visualize.py
+++ b/scripts/visualize.py
@@ -26,9 +26,13 @@ from unit_trace import visualizer
 
 # Get trace files from command line arguments
 from optparse import OptionParser
-parser = OptionParser()
+usage = "usage: %prog <one or more trace files>"
+parser = OptionParser(usage=usage)
 (options, traces) = parser.parse_args()
 traces = list(traces)
+if len(traces) < 1:
+    parser.print_help()
+    exit()
 
 ################################################################################
 # Pipeline