Groups of Data Files

If a group expression is used to specify a list of input data files (NDFs or positions lists), then file names may be specified that contain wild card characters ("*" and "?" - character classes can also be matched using strings such as "[0-9]", "[abcd]"). These will be expanded into a list of explicit file names before returning the group to the application.

If a group of output data files are specified by modification of a previously supplied group of input data files, the asterisk in the output group expression refers just to the file base-name (i.e. without directory path or file type). So, for instance, the group expression B_* would cause each output file name to be equal to the corresponding input file name, but with "B_" added to the start of the file base name. Thus an input file /home/dsb/data.fit would result in an output file /home/dsb/B_data.fit. If no directory is given in the output group expression, the directory associated with the input file is then added to the start of the file name. Likewise, any HDS path or file type is inherited from the input file if none are given in the output group expression.

If the final character in a group expression is a colon (:), then a list of the data files represented by the group expression (minus the colon) is displayed, but no data files are actually added to the group of files to be processed. The user is then re-prompted for another group expression, using the same parameter.

If an HDS container file² is supplied that contains two or more NDF structures, then each NDF within the container file is processed as a separate image. NDFs that are contained within an extension of another NDF are not included.

If a group of native output NDFs are created by modification of a group of native input NDFs (i.e. if the supplied string includes an asterisk), then the structure of each output container file will be copied from the corresponding input container file. For instance, if the container file o66_int.sdf contains 16 NDFs in components I1 to I16, then specifying "o66_int" when asked for a group of input images will result in all 16 NDFs being used. If the corresponding output images are specified using the string "*_A" then a single output file named o66_int_A.sdf will be created. The structure of this file will be copied from the input file, and will therefore contain the 16 output NDFs in components I1 to I16.