FID = fopen(FileName, 'r');
if FID == -1; error('Cannot read file'); end
Data = textscan(FID, '%s', 'delimiter', '\n', 'whitespace', '');
fclose(FID);
CStr = Data{1};
startWith_at = strncmp(CStr, '@', 1);
last_at = find(startWith_at, 1, 'last');
last_number = sscanf(CStr{last_at}, '@%d');
% Delete trailing lines:
CStr(last_at + 1:end) = [];
Do you want to write the file afterwards?
FID = fopen(FileName, 'w');
if FID == -1; error('Cannot read file'); end
fprintf(FID, '%s\n', CStr{:});
fclose(FID);
