require 1 argument

diff --git a/src/wheel-gen.pl b/src/wheel-gen.pl
index 27b9522197510ad1e1175e503f0016ad8d97623b..be03a6e3b0a481b44dd31a0cb98c0b56e4f00c70 100755 (executable)
--- a/src/wheel-gen.pl
+++ b/src/wheel-gen.pl
@@ -40,6 +40,9 @@ sub is_prime ($)
 }
 
 {
+  @ARGV == 1
+    or die "$program_name: missing argument\n";
+
   my $wheel_size = $ARGV[0];
 
   my @primes = (2);