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Defining the Extension List   

It is first necessary to define the set of specialist NDF extensions that should be recognised. This is normally done via the environment variable NDF_XTN, as follows:

setenv NDF_XTN CCDPACK,IRAS90

This is simply a comma-separated list of extension names conforming to the naming conventions described in SUN/33. It applies to all foreign format datasets, unless overridden. The order in which extensions occur in this list determines the order in which they will be imported. They will be exported in the reverse order.

On occasion, it may be necessary to use a different list of NDF extensions for a particular foreign format. Most commonly, this involves simply using an empty list for formats that do not require any extension handling (data compression of ordinary NDF data files would be an example - see §[*]). To specify a separate extension list for a particular foreign format, an environment variable is used whose name is constructed by prefixing `NDF_XTN_' to the format name (in upper case). For example:

setenv NDF_XTN_COMPRESSED ''

would over-ride the normal extension list with an empty one so that no extension handling would occur when COMPRESSED format data is accessed.



next up previous
Next: Extension Import and Export Commands
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Starlink System Note 20
R.F.Warren-Smith & D.S.Berry
17th July 2000
E-mail:ussc@star.rl.ac.uk

Copyright © 2000 Council for the Central Laboratory of the Research Councils