NDF Groups

 If a group expression is used to specify a list of input NDFs, then NDF names may be specified which contain wild card characters (``*'' and ``%'' on VMS, ``*'' and ``?'' on UNIX). These will be expanded into a list of explicit NDF names before returning the group to the application. Note, on UNIX systems group expressions containing wild-cards must be enclosed in quotes if they are supplied on the command line (this prevents the shell from expanding the wild-cards itself). Environment variables should not be included in NDF group expressions on UNIX.

If the final character in a group expression is a colon (:), then a list of the NDFs represented by the group expression (minus the colon) is displayed, but no NDFs are actually added to the group of NDFs to be processed. The user is then re-prompted for another group expression. Note, this facility only applies to group expressions representing existing NDFs, not NDFs which are to be created by the application.

If an IRAS90 application creates more than one output NDF, it will also create an output text file containing the names of the output NDFs in a form which can be used to specify the NDFs as input to another IRAS90 application. The text file is called iras90_ndfs.lis and is located in the users login directory. Succesive IRAS90 applications will over-write such text files created by previous applications. If such a file is created, then the global parameter DATA_ARRAY will be modified so that the suggested default for the input NDFs to the next application becomes an indirection element specifying the output NDFs from the previous application.

At the moment group expressions may only be used to specify NDFs which are stored at the top level of a container file.