how to get the line number having a specific string in a txt file - matlab

Question

I have a txt file that has a lot of content and in this file there is a lot of "include" word and I want to get data from all three lines after that.

myFile.txt: "-include:

-6.5 6.5

sin(x^2)

diff

-include

-5 5

cos(x^4)

diff"

How do I get this data in an array?

Answer 1

Based on your example (first include has : at the end, second one doesn't) you could use something like this.

fID = fopen('myFile.txt'); % Open the file for reading
textString = textscan(fID, '%s', 'Delimiter', '\n'); % Read all lines into cells
fclose(fID); % Close the file for reading
textString = textString{1}; % Use just the contents on the first cell (each line inside will be one cell)
includeStart = find(contains(textString,'include'))+1; % Find all lines with the word include. Add +1 to get the line after
includeEnd = [includeStart(2:end)-2; length(textString)]; % Get the position of the last line before the next include (and add the last line in the file)
parsedText = cell(length(includeStart), 1); % Create a new cell to store the output
% Loop through all the includes and concatenate the text with strjoin
for it = 1:length(includeStart)
  parsedText{it} = strjoin(textString(includeStart(it):includeEnd(it)),'\n');
  % Display the output
  fprintf('Include block %d:\n', it);
  disp(parsedText{it});
end

Which results in the following output:

Include block 1:
-6.5 6.5
sin(x^2)
diff
Include block 2:
-5 5
cos(x^4)
diff

You can tune the loop to suit your needs. If you just want line numbers, use includeStart and includeEnd variables.