extern int run_copy_in (const char *cmd, size_t argc, char *argv[]);
extern int run_copy_out (const char *cmd, size_t argc, char *argv[]);
+/* in display.c */
+extern int run_display (const char *cmd, size_t argc, char *argv[]);
+
/* in echo.c */
extern int run_echo (const char *cmd, size_t argc, char *argv[]);