Delete lines from text file

Question

Sergio 2013-8-29

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/85961-delete-lines-from-text-file

评论： Josh Murman 2020-3-26

采纳的回答： Image Analyst

How can I delete all the lines form a text file after the line number x and store it in another test file?

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Answer 1

Image Analyst 2013-8-29

2
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/85961-delete-lines-from-text-file#answer_95486

在 MATLAB Online 中打开

As shown in the help:

fid = fopen('fgetl.m');
tline = fgetl(fid);
while ischar(tline)
    disp(tline)
    tline = fgetl(fid);
end
fclose(fid);

Now just modify that to open 2 files, and add a line counter then break after you've transferred x of them (untested)

fin = fopen('input.txt');
fout = fopen('output.txt', 'wt');
tline = fgetl(fin);
count = 0;
while ischar(tline) && count < x
    disp(tline)
    tline = fgetl(fin);
    if ischar(tline)
        fprintf(fout, '%s\n', tline);
    end
    count = count + 1;
end
fclose(fin);
fclose(fout);

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Sergio 2013-8-29

this worked perfect! Thank you!

Josh Murman 2020-3-26

在 MATLAB Online 中打开

Add ~strcmp(tline,'Expected Line Text to Remove') to the if statement if you would like to remove a line with that string. Also move the fgetl function in the while loop so the first line isn't skipped.

fin = fopen('input.txt');
fout = fopen('output.txt', 'wt');
tline = fgetl(fin);
while ischar(tline)
    if ~strcmp(tline,'Expected Line Text to Remove') && ischar(tline)
        fprintf(fout, '%s\n', tline);
    end
    tline = fgetl(fin);
    count = count + 1;
end
fclose(fin);
fclose(fout);

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Answer 2

dpb 2013-8-29

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/85961-delete-lines-from-text-file#answer_95487

Read line 1:x from 1 and copy to the second. Close the second. Done.

Alternatively, rather than line-by-line, read the whole file if it's small enough to fit in memory relatively easily and if x is a sizable fraction of the total number of lines. Then just save data(1:x,:) to the new file.

That's the thing about sequential files---they're, well, 'sequential'.