How to delete every nth lines in a txt file?

Question

I have a txt file (ANSYS 1ST principle nodal stress list) and there are almost 16k lines inside of it. I wanna delete specific lines for example 1st, 2nd, 3rd, 4th, 5th, 39th, 40th, 41th, 42th, 43th, etc. I dont need to search anything, i know which lines be deleted. is there anybody help?

Did you see this ? https://www.mathworks.com/matlabcentral/answers/159783-how-to-delete-specific-lines-from-a-txt-file — Mohammadreza Khatami, Jan 05 '19 at 11:32

score 1 · Answer 1 · answered Jan 05 '19 at 11:12

1

If you are using linux you can use that command:

sed -i '2d' data.txt

answered Jan 05 '19 at 11:12

strash

1,291
2
15
29

score 1 · Accepted Answer · answered Jan 05 '19 at 11:58

Maybe not the most efficient way but this works:

data_file = 'data.txt';
lines_to_skip = [1:5, 39:43];

fid = fopen(data_file);
ii = 0;
while ~feof(fid)
    ii = ii + 1;
    file_content{ii} = fgetl(fid);
end

lines = true(1,ii);
lines(lines_to_skip) = false;
fid = fopen(data_file,'w');
fprintf(fid,'%s\r\n',file_content{lines});
fclose(fid);

score 0 · Answer 3 · answered Jan 05 '19 at 11:25

This is tagged as Matlab, but doing this inside Matlab is going to be painful because it doesn't usually offer a convenient way to remove bytes in the middle of a file, so you'd have to write some code to write the text to a new file, skipping lines as appropriate.

If you're on a UNIX system it'll be much easier using sed. There's a great answer here explaining how to do that. The key command is:

# To delete line 10 and 12:
sed -i -e '10d;12d' your-file.txt

How to delete every nth lines in a txt file?

3 Answers3