MATLAB: How to adjust and save a .txt file within a for loop

for looptxt

I have a .dpj file which is in fact a normal .txt file. I would like to open, change a number, save under a specific name and close the file all within a for loop without loosing the basic file.
My question is how I can do this for example if the number is standing in the line 100 of the text file behind KLEFF?
The filename under which I want to save the .dpj file should be numbered depending on the for loop.
By myself this part works except that the .dpj files are not readable anymore:
N=10;
for i=0:N;
  baseline_name='textfile';
  filename=[baseline_name,'_',num2str(i)];
  savename=strcat(char(filename),'.dpj');
  save (savename);
end
Many thanks in advance!

Best Answer

Folder = cd;  % Set accordingly
N = 10; 
for iFile = 0:N
  % Read the text:
  File = fullfile(Folder, sprintf('textfile%d.dpj', iFile));
  Str  = fileread(File);
  CStr = strsplit(Str, '\n');
    % Change the line:
    Line = CStr{100};
    Line = [strtok(Line, '='), sprintf('= %g', rand)];
    CStr{100} = Line;
    % Write the text:
    NewFile = fullfile(Folder, sprintf('textfile%d_modified.dpj', iFile));
    fid = fopen(NewFile, 'w');
    if fid == -1
      error('Cannot open file for writing: %s', FileName);
    end
    fprintf(fid, '%s\n', CStr{:});
    fclose(fid);
  end
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