$NetBSD: patch-ae,v 1.3 1999/01/10 23:52:16 tron Exp $

--- pbm/pbmmerge.c.orig	Wed Nov  3 10:28:55 1993
+++ pbm/pbmmerge.c	Sun Jan 10 23:48:40 1999
@@ -29,6 +29,10 @@
 	{
 	++argv;
 	--argc;
+	if(!*argv)	{
+		fprintf(stderr, "Usage: pbmmerge pbm_program_name [args ...]\n");
+		exit(1);
+		}
 	goto again;
 	}