MATLAB: Removing double empty lines from a text file

double repetitionsempty linestext file

If a file contains more than one consecutive empty lines, they are replaced by one empty line.
% reading file
fid=fopen(outFile,'rt');
Data = textscan(fid,'%s','Delimiter','\n');
Data=Data{1}; % get rid of nesting
k=1; emptylines_occured=0;
for j=1:numel(Data)
    if ~strcmp(Data(j),'') % not empty line
       if emptylines_occured
         newData{k}=''; k=k+1;
         emptylines_occured=0;
       end
       newData(k)=Data(j); k=k+1;
    else % empty line
       emptylines_occured=1;
    end
end
fclose(fid);
% writing file
fid=fopen(outFile,'wt');
for j=1:numel(newData)
  fprintf(fid, '%s\n',newData{j});
end
fclose(fid);
Is there a more concise way?

Best Answer

You can easily write the new file at the same time as you read the old one, which is faster and uses much less memory. Here is a simple version that create the new file with at most one empty line between any two non-empty lines:
[f1d,msg] = fopen('test_old.txt','rt');
assert(f1d>=3,msg)
[f2d,msg] = fopen('test_new.txt','wt');
assert(f2d>=3,msg)
prv = 'X';
while ~feof(f1d)
    new = fgetl(f1d);
    if numel(new) || numel(prv)
        fprintf(f2d,'%s\n',new);
    end
    prv = new;
end
fclose(f1d);
fclose(f2d);
The test files are attached. Define prv as an empty char to ignore the leading empty line/s.
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