15.64.18.22  FILE   - FILE=filename - This selects the device and filename
for output.  This option only  works  for  non-interactive  or  sequential
devices.   If you wish to specify a file name containing either semicolons
or blanks, it must be enclosed in parenthesis.

CHANNEL=DEV:   -  This selects the output device.  For interactive devices
or slave devices this is your terminal by default.

You  either  select  a  device or filename.  Interactive and slave devices
generally accept CHANNEL,  while  sequential  devices  accept  FILE.   The
TEKTRONIX and REGIS devices treat FILE and CHANNEL as synonyms.