how to open an external text file, identify two strings and save the lines of the text file where the two strings appear

Question

Hugo 2021-3-12

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回答： Jan 2021-6-29

sample_text.txt

Hi,

I would like to open an external text file, identify two strings, for example "Pattern1" and "Pattern2" and save in two variables, line1 and line2, the number of the line of the text file where "Pattern1" and "Pattern2". I am attaching the text file. In this example line1=12 and line2=24

I thank you in advance,

Best regards,

Hugo

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Jan 2021-3-12

Is this a homework?

Use: fileread, strsplit, find(strcmp()).

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Answer 1

Mathieu NOE 2021-3-12

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https://ww2.mathworks.cn/matlabcentral/answers/770688-how-to-open-an-external-text-file-identify-two-strings-and-save-the-lines-of-the-text-file-where-th#answer_646028

在 MATLAB Online 中打开

hello Hugo

see below

Filename = 'sample_text.txt';
[Pattern1_line, Pattern2_line] = extract_data(Filename);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function [Pattern1_line, Pattern2_line] = extract_data(Filename)
fid = fopen(Filename);
tline = fgetl(fid);
% initialization
k = 0;
p = 0;
q = 0;
Pattern1_line = 0;
Pattern2_line = 0;
while ischar(tline)
    
    k = k+1;    % loop over line index
    
   % retrieve line Date/Time
    if contains(lower(tline),'pattern1')   % lower make matlab not case sensitive
        Pattern1_line = k;
    end
   
   % retrieve line Date/Time
    if contains(lower(tline),'pattern2')   % lower make matlab not case sensitive   
        Pattern2_line = k;
    end
    
tline = fgetl(fid);
end
fclose(fid);
end

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Jan 2021-6-29

Note: contains has an option to ignore the case. This is more efficient than lower() of the input.

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Answer 2

Jan 2021-6-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/770688-how-to-open-an-external-text-file-identify-two-strings-and-save-the-lines-of-the-text-file-where-th#answer_736028

在 MATLAB Online 中打开

S = fileread('sample_text.txt');
C = strsplit(S, '\n');
Pattern1_line = find(contains(C, 'Pattern1', 'IgnoreCase', true));
Pattern2_line = find(contains(C, 'Pattern2', 'IgnoreCase', true));