diff -rauN cku302/ckucmd.c cku302-ckucmd-IO_file_flags-patch/ckucmd.c
--- cku302/ckucmd.c	2011-07-14 14:14:37.000000000 +0200
+++ cku302-ckucmd-IO_file_flags-patch/ckucmd.c	2019-06-17 14:19:01.124728510 +0200
@@ -7370,6 +7370,7 @@
 
 /* Here we must look inside the stdin buffer - highly platform dependent */
 
+#define _IO_file_flags
 #ifdef _IO_file_flags			/* Linux */
     x = (int) ((stdin->_IO_read_end) - (stdin->_IO_read_ptr));
     debug(F101,"cmdconchk _IO_file_flags","",x);