Index: Demo/comparisons/regextest.py
===================================================================
--- Demo/comparisons/regextest.py	(revisão 86649)
+++ Demo/comparisons/regextest.py	(cópia de trabalho)
@@ -16,6 +16,15 @@
 # - is only about 2.5 times as slow as egrep (though I couldn't run
 #   Tom's test -- this system, a vanilla SGI, only has /etc/terminfo)
 
+# Usage:
+#
+#    $ cat pattern | python3 regextest.py FILENAME
+#
+# You can use bash substitution wildcards:
+#
+#    $ cat pattern | python3 regextest.py *
+#
+
 import string
 import sys
 import re
@@ -25,6 +34,9 @@
     bigpat = '(' + '|'.join(pats) + ')'
     prog = re.compile(bigpat)
 
+    if len(sys.argv) < 2:
+        usage()
+
     for file in sys.argv[1:]:
         try:
             fp = open(file, 'r')
@@ -40,6 +52,16 @@
             if prog.search(line):
                 print("%s:%s:%s" % (file, lineno, line), end=' ')
 
+def usage():
+    print('''Usage:
+
+    $ cat pattern | python3 regextest.py FILENAME
+
+You can use bash substitution wildcards:
+
+    $ cat pattern | python3 regextest.py *
+''')
+
 def chomp(s):
     return s.rstrip('\n')