FUNCTION: cdf_file_names PURPOSE: Returns an array of filenames within a timerange. USAGE: files=cdf_file_names(FORMAT,trange=trange,/verbose) INPUT: FORMAT is a string that will be interpreted as one of two things: CASE 1: e.g. FORMAT = '/home/wind/dat/wi/3dp/k0/????/wi_k0_3dp*.cdf' if FORMAT contains * or ? then filenames are returned that match that pattern and for which YYYYMMDD falls within the specified timerange. for example: (UNIX only) CASE 2: e.g. FORMAT = 'fa_k0_ees_files' The name of an indexfile that associates filenames with start and end times. If his file is not found, then the environment variable getenv('CDF_INDEX_DIR') is prepended and searched for. See "make_cdf_index" for information on producing this file. SPECIAL NOTE: If strupcase(FORMAT) is the name of an environment varible. Then the value of that environment variable is used instead. KEYWORDS: TRANGE: Two element array specifying the time range for which data files should be returned. If not provided then "timerange" is called to provide the time range. See also "timespan". NFILES: Named variable that returns the number of files found. VERBOSE: Set to print some useful info. FILEINFO: OBSOLETE! Set to a named variable that will return a table of file info. NOTES: UNIX only!