how to count the number of lines of an external txt file

Question

Hugo 2022-5-2

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https://ww2.mathworks.cn/matlabcentral/answers/1709720-how-to-count-the-number-of-lines-of-an-external-txt-file

评论： Rik 2022-5-2

a.txt

Hi,

I would like to know how I can count the number of lines (not empty) of an external text file, let's say, a.txt, and save it in a variable.

Best regards,

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Answer 1

Davide Masiello 2022-5-2

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a.txt

Not sure if there is a better way, but this will work

fid = fopen('a.txt','r');
n = 0;
while ~feof(fid)
    fgetl(fid);
    n = n+1;
end
fclose(fid);
n
n = 15

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Rik 2022-5-2

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Your code doesn't skip empty lines in the middle of the file

% Write an example file with a blank line
fid=fopen('a.txt','w');
fprintf(fid,'line1\n\nline3\n');
fclose(fid);
% Run your code
fid = fopen('a.txt','r');
n = 0;
while ~feof(fid)
    fgetl(fid);
    n = n+1;
end
fclose(fid);
n
n = 3

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Answer 2

Rik 2022-5-2

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https://ww2.mathworks.cn/matlabcentral/answers/1709720-how-to-count-the-number-of-lines-of-an-external-txt-file#answer_955330

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The problem with your question is that it lacks a definition of line. If your file ends with char(10) or char(13) does that signify a new line (meaning you have a trailing empty line)?

txt=readfile('https://www.mathworks.com/matlabcentral/answers/uploaded_files/985140/a.txt',...
    'EmptyLineRule','skip')
txt = 15×1 cell array
    {'asd'}
    {'er' }
    {'234'}
    {'sdf'}
    {'dfh'}
    {'fy' }
    {'578'}
    {'fg' }
    {'dfg'}
    {'w34'}
    {'dfg'}
    {'df' }
    {'fh' }
    {'yu' }
    {'19' }
a=numel(txt)
a = 15

This is the choice that my readfile function makes. If you use R2020b or later you will be able to use the builtin readlines function. For older releases (or GNU Octave) you will need to use readfile.