enable ncl logging

    This will begin the logging of ncl commands to the NCL log file.
    This log file must be established earlier in the NCL session with
    the "set ncl logfile" command.

    For example, on OpenVMS:

    NCL>set ncl logfile test
    NCL>enable ncl logging
    NCL>show all
    NCL>disable ncl logging
    NCL>show ncl logfile
    Logfile name is: test
    Logfile is Disabled

    The results will be in the file TEST.NCL.  That file will contain
    the logged NCL command(s), and the output will be commented out.
    You may then reissue the command(s) you logged by:

    NCL>do test.ncl