extern command_ret_t do_echo(cmd_tbl_t *, uint_fast8_t, int, char * const []);
extern command_ret_t do_sleep(cmd_tbl_t *, uint_fast8_t, int, char * const []);
extern command_ret_t do_env_print(cmd_tbl_t *, uint_fast8_t, int, char * const []);
extern command_ret_t do_echo(cmd_tbl_t *, uint_fast8_t, int, char * const []);
extern command_ret_t do_sleep(cmd_tbl_t *, uint_fast8_t, int, char * const []);
extern command_ret_t do_env_print(cmd_tbl_t *, uint_fast8_t, int, char * const []);