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

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

[Jan]

Is this a homework?

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

Answer 1

[Mathieu NOE]

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

[Jan]

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

Answer 2

[Jan]

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));

Answer 3

[Hugo]

Dear Mr. Mathieu,

Thank you for your help. Unfortunately, your solution does not work on my end. Do you have other suggestions?

[Mathieu NOE]

strange

what is the error message ?

[Hugo]

Hi,

I don't get any error. I just don't get any output file with the data I want to filter. Do you have any other suggestion?

[Mathieu NOE]

hello

you should get the two variables in your workspace

that's what the line :

[Pattern1_line, Pattern2_line] = extract_data(Filename);

does.

proof :

I got in my workspace :

Pattern1_line = 12

Pattern2_line = 24

Now if you want to save it in a output file, I didn't code it but I suppose you know how to do it