MATLAB: Matlab freeze when fprintf to file

fprintfmatlab freezewrite file

Hi
I have a large amount of data, many years. It is given in daily files.
For reasons irrelevant for the question I have to combine these files to yearly data files ~ 3Gb.
The daily files are of .cdf format and contain more variables than needed and also lack some that has to be derived.
The following shows an example that makes my computer freeze for around 5 min. But that data datafile is complete with seconds.
fid = fopen('test.m', 'w');
data = randi(5, 40000, 10);
for i=1:2 %5
    fprintf(fid, '%d %d %d %d %d %d %d %d %d %d\n', data);
end
fprintf(fid, '%d %d %d %d %d %d %d %d %d %d\n', zeros(1, 10)); %Newly added line
fclose(fid)
Does anyone know why it freezes for so long when the files is written so fast?
Using Matlab R2018a on a remote desktop with Ubuntu OS

Best Answer

Instead of 'test.m', write to 'test.txt' or something else. The fprintf is fast, but having a "test.m" file in the current directory seems to freeze Matlab.
fid = fopen('test.txt', 'w'); %Don't write to .m files, unless it's a matlab file type
data = randi(5, 40000, 10);
for i=1:2 %5
    fprintf(fid, '%d %d %d %d %d %d %d %d %d %d\n', data);
end
fprintf(fid, '%d %d %d %d %d %d %d %d %d %d\n', zeros(1, 10)); %Newly added line
fclose(fid)
My Matlab also freezes when there is a "test.m" file in the current directory that Matlab cannot determine if it's a script or function - it just says it's a "Matlab Code File". I'm guessing this step for determining what file type this "test.m" file is causes Matlab to freeze. I think this should go into the bug report for 2017 versions - not sure if 2018 version fixed this.
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