replacing the content of a text file

Hi all. I have a text file "A.txt". I have a string S='Hello World'.

How to delete from line 10 to the end of file in "A.txt" and replace those deleted contents by string S, and save the new file to "B.txt"?

[Paolo]

What's your OS? Can you show contents of "A.txt" ?

[H R]

Windows 10. Please see the attached.

Answer 1

[Image Analyst]

Try this:

S='Hello World';

% Open the input file for reading.
fullInputFileName = 'A.txt';
inputFileID = fopen(fullInputFileName, 'rt');
% Open the input file for reading.
fullOuputFileName = 'B.txt';
outputFileID = fopen(fullOuputFileName, 'wt');
% Transfer the first 9 lines.
for k = 1 : 9
  % Read the line.
  textLine = fgetl(inputFileID);
  fprintf('Transferring line #%d: "%s"\n', k, textLine);
  % Write the line.
  textLine = fprintf(outputFileID, '%s\n', textLine);
end
% Write S to B.txt
textLine = fprintf(outputFileID, '%s\n', S);

% All done reading all lines, so close the file.
fclose(inputFileID);
fclose(outputFileID);

fprintf('\n--------------------------------\nHere is B.txt:\n');
type(fullOuputFileName);