function [files]=get_files_from_TDS(url_base);
% GET_FILES_FROM_TDS  Return list of NetCDF files found in a URL directory
% of a THREDDS opendap server
s=urlread(url_base);
f2=strfind(s,'.nc');
k=0;
% for the THREDDS data, there will be 2 .nc's found for every file.
% our file names aren't longer than 25 characters
for i=2:2:length(f2);
    k=k+1;
    tmp=s(f2(i)-25:f2(i)+2);
    idx=strfind(tmp,'<tt>');  % <tt> preceeds the file name in all cases
    files{k}=tmp(idx+4:end);
end
% repeat for cdf.
f2=strfind(s,'.cdf');
for i=2:2:length(f2);
    k=k+1;
    tmp=s(f2(i)-25:f2(i)+3);
    idx=strfind(tmp,'<tt>');  % <tt> preceeds the file name in all cases
    files{k}=tmp(idx+4:end);
end

% the roots and catalogs don't always match which causes trouble
% for stellwagen url_base should look like:
% http://stellwagen.er.usgs.gov/thredds/catalog/TSdata/ARGO_MERCHANT/catalog.html
% but the individual path to the file is:
% http://stellwagen.er.usgs.gov/thredds/dodsC/TSdata/ARGO_MERCHANT/1211-A1H.cdf
%
% the coast-enviro equivalent url_base is:
% http://coast-enviro.er.usgs.gov/thredds/ts/ARGO_MERCHANT.html
% with the individual files at:
% http://coast-enviro.er.usgs.gov/thredds/dodsC/ARGO_MERCHANT/1211-A1H.cdf