how to extract a specific text/string from text file

I have the following text file:

.................................................................

POS, 619857792, 41.6477224, -4.2899403, 874.34, -12.55482

IMU, 619875777, -0.06479891, 0.2502703, 0.0502184, -0.4383386, -0.129217, -14.2286, 0, 0, 32.03047, 1, 1

IMU2, 619875777, -0.08689992, 0.2353809, 0.04117718, -0.756902, 0.09682357, -14.2211, 0, 0, 34.875, 1, 1

CAM, 619876179, 469709600, 2132, 41.6477203, -4.289937, 874.33, -11.96, 873.32, 2.73, 0.55, 106.3

ARSP, 619876621, 15.70767, 136.6173, 11.25, 136.6173, 1.993906, 1

IMU, 621675604, -0.005321865, 0.09623767, 0.01352201, -0.5002327, 0.789924, -10.80867, 0, 0, 31.89751, 1, 1

IMU2, 621675604, -0.03922234, 0.1098862, 0.009741771, -0.5334755, 0.7404263, -10.89349, 0, 0, 34.625, 1, 1

CAM, 621676033, 469711400, 2132, 41.6475301, -4.2896673, 875.32, -10.97, 873.98, -2.65, 4.01, 111.77

MAG, 621676323, -107, -268, 373, 93, -78, -30, 0, 0, 0, 1, 621676239

MAG2, 621676323, -137, -168, 253, 145, 211, -550, 0, 0, 0, 1, 621676242

ARSP, 621676575, 14.68222, 119.3618, 11.25, 119.3618, 1.993906, 1

............................................................................................................................

I want to extract the lines with the item CAM, so the result is:

CAM, 619876179, 469709600, 2132, 41.6477203, -4.289937, 874.33, -11.96, 873.32, 2.73, 0.55, 106.3

CAM, 621676033, 469711400, 2132, 41.6475301, -4.2896673, 875.32, -10.97, 873.98, -2.65, 4.01, 111.77

Can someone help me with this the code? Thank you very much

[Rik]

What did you try? Do you already know how to read your file to a Matlab variable? Are you running R2020b?

[Iñigo Molina Sánchez]

Rik, Thank you very much for your answer. Yes, I'm running R2020b. I tried something like this:

   fid = fopen('2020-11-20 11-23-40.log','r');
        while ~feof(fid)
        st = fgetl(fid);
            if  ~isempty(findstr(st,'CAM,'))
            ftell(fid)
            fseek(fid,-9,0)
            F = cell2mat(textscan(fid,'%5d')) 
         end
       end

However, i know I'm doing something wrong

Answer 1

[Image Analyst]

Try this:

% Open the file for reading in text mode.
fileID = fopen(fullFileName, 'rt');
% Read the first line of the file.
textLine = fgetl(fileID);
lineCounter = 1;
while ischar(textLine)
	% Print out what line we're operating on.
	fprintf('%s\n', textLine);
	% See if this line starts with CAM
	if startsWith(textLine, 'CAM')
		% Do something with this line.
	end
	% Read the next line.
	textLine = fgetl(fileID);
	lineCounter = lineCounter + 1;
end
% All done reading all lines, so close the file.
fclose(fileID);

[Iñigo Molina Sánchez]

Thank you very muy for your help. I'm trying your code. Iguess, I just can write something like fprint(textline) after the if statement for retrieveng the CAM string

[Iñigo Molina Sánchez]

Thank you so much. The final code is:

% Open the file for reading in text mode .
fileID = fopen('2020-11-20 11-23-40.log', 'rt');
fiD2 = fopen('CAMfile.csv','w');
% Read the first line of the file .
textLine = fgetl(fileID );
lineCounter = 1 ;
while ischar(textLine )
% Print out what line we're operating on .
fprintf('%s\n', textLine );
% See if this line starts with CAM
if startsWith(textLine, 'CAM,')
% Do something with this line .
fprintf(fiD2,'%s\n',textLine;
end
% Read the next line .
textLine = fgetl(fileID );
lineCounter = lineCounter + 1 ;
end
% All done reading all lines, so close the file .
fclose(fileID);

[Rik]

You forgot to fclose the second file.

[Iñigo Molina Sánchez]

Hi Rik, I agree completely with you. Indeed, I already add the corresponding sentence.

Thank you very much again!

[Image Analyst]

I'd probably open the output file as text explicitly with the 'wt' option since a CSV file is just a plain, flat text file:

fiD2 = fopen('CAMfile.csv', 'wt');

Answer 2

[Rik]

You can either use my readfile function (which you can get from the file exchange or the add-on manager). Another option is to use the readlines function.

Once you have read the file with either of these functions, you can use contains to create a logical array to index it:

Data=readfile(filename);
Data=Data(contains(Data,'CAM'));

[Iñigo Molina Sánchez]

Thank you very much Rik. I wil try your suggestions.