Removing double empty lines from a text file

Question

bbb_bbb 2018-2-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/381467-removing-double-empty-lines-from-a-text-file

编辑： Stephen23 2018-2-9

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?

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Birdman 2018-2-8

Can you share your file?

bbb_bbb 2018-2-8

This may be any text file, e.g. an m-file.

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Answer 1

Stephen23 2018-2-8

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https://ww2.mathworks.cn/matlabcentral/answers/381467-removing-double-empty-lines-from-a-text-file#answer_304074

编辑：Stephen23 2018-2-9

在 MATLAB Online 中打开

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.

3 个评论
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Stephen23 2018-2-8

@Walter Roberson: the original question uses the t option for both reading and writing, so presumably this is not a problem.

bbb_bbb 2018-2-9

编辑：Stephen23 2018-2-9

This works excellently. Thanks.

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Answer 2

Walter Roberson 2018-2-8

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/381467-removing-double-empty-lines-from-a-text-file#answer_304079

编辑：Walter Roberson 2018-2-8

在 MATLAB Online 中打开

%read the file _and_ do the work of deleting extra empty lines.
new_text = regexprep( fileread(outFile), '(\r?\n)(\r?\n)+', '$1');
%write the result to a new file
fid = fopen('text_new.txt', 'w');
fwrite(fid, new_text);
fclose(fid)