% touch_gmeta change a global attribute in a series of files
%
% touch_gmeta(gatt, newval, files, dryrun)
% gatt = global attribute name
% newval = new attribute value
% files = cell array of file names
%   an easy way to just use a pattern:
%   d = dir('844*.nc');
%   touch_gmeta('MOORING','844',{d.name},1)
% dryrun = 1;   test run first, set to zero to execute
%

% Written by Marinna Martini with guidance from Ellyn Montgomery
function touch_gmeta(gatt, newval, files, dryrun)

if ~exist('dryrun','var'), 
    dryrun = 1; 
end

if dryrun, disp('This is a dry run, nothing will be changed'); end
%  NOTE : this only works on files in the cwd- it doesn't traverse dirs to
%  find files to modify !!
%   ** needs to work with either nc or cdf
if ~exist('files','var'),
    if ispc
        d1=dir('*.nc');
        d2=dir('*.cdf');
        d=[d1;d2];
        for jj=1:length(d)
            fnames{jj}=d(jj).name;
        end
    else              % for unix
        [stat,fnamesames]=unix('ls *');
        knt=1;
        for ik=1:length(xx)-1
            vv=char(deblank(fnamesames(xx(ik):xx(ik+1)-1)));
            if(~isempty(findstr(vv,'cdf')) || ~isempty(findstr(vv,'nc')))
                fnames{knt}=deblank(fnamesames(xx(ik):xx(ik+1)-1));
                knt=knt+1;
            else
                disp(['not processing ' vv]);
            end
        end
    end
else 
    fnames = files;
end
for ifile=1:length(fnames)
    nc = netcdf(fnames{ifile}, 'write');
    if isempty(nc), disp('read of ncfile failed, try another name'), return, end

    eval(sprintf('gattobj = nc.%s(:)',gatt))
    if ~isempty(gattobj),
        disp(sprintf('%s nc.%s(:) = newval;',fnames{ifile},gatt));
        disp(newval)
        command = sprintf('nc.%s(:) = newval;',gatt);
        if ~dryrun, eval(command); end
    else
        disp(sprintf('%s not found in %s',gatt, fnames{ifile}))
    end

    close(nc)
end