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The Syntax for Specifying Groups of Data Files

The group of NDFs or positions lists to be used for a given parameter is specified by a group expression. This is also the syntax used to give groups of plotting attributes when specifying graphics STYLE parameters. The group expression syntax is described here.

A group of output data files may be specified by modifying the names of a corresponding set of input data files. This is easy enough when the application only has one parameter for input data files, but what happens if more than one parameter is associated with a group of input data files? Which parameter is used to define the group of input data files on which the names of the output data files are based? The answer is ``the first one to be accessed''. For instance, ADD takes two input NDFs, adds them together and produces a single output NDF. When running ADD, you are prompted first for Parameter IN1, and then for Parameter IN2, and finally for Parameter OUT. Thus, if you give the string "a_"* for OUT, the names of the output NDFs will be derived from the NDFs supplied for Parameter IN1, because IN1 is accessed first (i.e. prompted for before IN2).

Note, when choosing the input parameter on which output data files are based, no significance is attached to whether the input and output file types match. That is, the first input parameter to be accessed if used, irrespective of whether it is associated with an NDF or a positions list.

A feature that may sometimes be useful is the facility for providing a shell command in response to a prompt for a group of data files. To do this, enclose the command within the usual backward quotes (`), as you would when substituting the output from a command into another shell command. The command should generate a set of explicit file names, with file types. Note, you will need to escape any characters that are normally interpreted as part of the syntax of a group expression, such as "|" or ",", by preceding them with a backslash "\".


next up previous 530
Next: Using non-NDF Data Formats
Up: Processing Groups of Data Files
Previous: Reporting the Data Files being Processed

KAPPA --- Kernel Application Package
Starlink User Note 95
Malcolm J. Currie & David S. Berry
2013 February 14
E-mail:starlink@jiscmail.ac.uk

Copyright © 2013 Science and Technology Facilities Council