
  keyword <buffer> (KEYWORD) [variable] [-w value]

  "keyword" extracts the specified keyword from the header of the
   specified buffer.  If a third word is listed, the value of the
   keyword is stored in a variable with the given name.  If the -w
   option is given, the value is written to the header keyword.

   The header Meta-data is well-defined for FITS, but not necessarily
   for other data types.

