P.S. If you just type lsnrctl you get yourself to listener prompt and query, start, stop listener not Intelligent Agent:
$ lsnrctl

LSNRCTL for DEC OSF/1 AXP: Version 8.1.6.0.0 - Production on 05-DEC-2000 21:02:50

(c) Copyright 1998, 1999, Oracle Corporation. All rights reserved.

Welcome to LSNRCTL, type "help" for information.

LSNRCTL> status
Connecting to (ADDRESS=(PROTOCOL=TCP)(Host=166.34.207.20)(Port=1521))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for DEC OSF/1 AXP: Version 8.1.6.0.0 - Production
Start Date 29-NOV-2000 00:36:30
Uptime 6 days 20 hr. 26 min. 24 sec
Trace Level off
Security OFF
SNMP ON
Listener Parameter File /usr/local/oracle/product/8.1.6/network/admin/listener.ora
Listener Log File /usr/local/oracle/product/8.1.6/network/log/listener.log
Services Summary...
INS1 has 1 service handler(s)
INS1 has 1 service handler(s)
The command completed successfully