legacy/src/main/java/ucar/nc2/NetcdfFileWriteable.java
static public NetcdfFileWriteable openExisting(String location, boolean fill) throws IOException {
    return new NetcdfFileWriteable(location, fill, true);
  }
static public NetcdfFileWriteable openExisting(String location, boolean fill) throws IOException {
    return new NetcdfFileWriteable(location, fill, true);
  }
Open an existing Netcdf file for writing data.
Cannot add new objects, you can only read/write data to existing Variables.
Setting fill = false is more efficient, use when you know you will write all data.

@param location name of existing file to open.
@param fill     if true, the data is first written with fill values.
@return existing file that can be written to
@throws IOException on I/O error