MATLAB: How to select next specific line based on string present in previous line and copy the line also from a text file

Question

x='$RAIM';
y='$GPGGA';
fid=fopen('myfile.txt');
while ~feof(fid)
  tline = fgetl(fid);
  if contains(tline,x)
      fprintf(id,'%s\n',tline)
end
end
fclose(fid)

% Input file contents

$RAIM,002212,003080,000818,001156,020000,020000,000777,001098,111,3,11111111*32
$GPGGA,151943.50,1257.32717,N,07738.23927,E,2,09,0.87,823.3,M,,M,,*44.

if second last column of RAIM line is 5 not 3 then only select GPGGA line otherwise go to next line.

Answer 1

S = fileread('myfile.txt');
gpgga_lines = regexp(S, '(?<=^\$RAIM,.*,5,[^,]*$)\$GPGGA,.*$', 'match', 'lineanchors', 'dotexceptnewline');