Trying to delete lines that start with an alphabet on a text file

Hi folks,

I have a huge textfile right here with around 100k lines and I am trying to delete all the lines that start with an alphabet (not deleting the ones that start with numbers). Can anybody help? I am having trouble structuring the m file.

Thanks.

Answer 1

[Guillaume]

Use fopen, fgetl, fclose to read your file into a cell array and discard the lines you don't want. Or if you want to write a new file, use fopen, fprintf, fclose and write as your read:

fidi = fopen('somefile.txt', 'rt');
fido = fopen('newfile.txt', 'wt');
tline = fgetl(fidi);
while ischar(tline)
  if ~isempty(tline) && tline(1) >= '0' && tline(1) <= '9'
    %line to keep
    fprintf(fido, '%s\n', tline);
  end
  tline = fgetl(fidi);
end
fclose(fidi);
fclose(fido);

edit: forgot to read the next line!

[mt]

I tried it with a smaller text file, but 'Run' never ends for this code. What could be wrong?

[Guillaume]

Yep, I forgot a

tline = fgetl(tline);

within the loop. (You could have found that out in the documentation of fgetl that I linked).

I've edited my answer.