Propagating Data Formats

The output format may also be determined according to the format of a related input dataset. This is achieved by putting the ``wild-card'' character `$*$' at the start of the output format list, as follows:

setenv NDF_FORMATS_OUT '*,.,FIGARO(.dst),FITS(.fit),IRAF(.imh)

This affects new datasets which are created as a result of the propagation of information from an existing dataset (e.g. by applications calling the routines NDF_PROP or NDF_SCOPY, as described in SUN/33) and for which no explicit output file extension is given. In this instance, not only will data values be propagated, but so also will the dataset format. Thus, if a FIGARO format dataset (with file extension `.dst') had been accessed for input and propagated to create an output dataset, then a similar FIGARO format dataset would be created (also with a `.dst' file extension) unless an explicit output file extension were given.⁶

Note that output datasets which are created by applications without propagation from an existing dataset do not inherit any format information. In this case, any `$*$' in the format list is ignored and the normal rules apply (in the example above, a native format NDF dataset would be created instead).