Dbms_pipe is another way of doing this. In the pl/sql send a message
and that is captured by the daemon running on the background.
Based on the message sent by the pl/sql , daemon would do the
required job. As daemon runs on the background , it is easy
to execute the host command.
The disadvantage of this is to have a daemon running in the background.

As suggested earliear, for oracle 8i , external procedure is a good
option.