Concatenate data using fgets

I want to read a data pattern from a txt file and concatenate each line together. I wrote the following program but the error message shows:

function read_datapattern(filename)
fid = fopen(filename,'rt');
if fid < 0
  error('error opening file %s\n\n',filename);
end
pattern = fgets(fid);
for n = 1:32767
  nextline = fgets(fid);
  pattern = strcat(pattern, nextline);
fprintf(pattern);
fprintf('\n');
fclose(fid);
end

"Invalid file identifier. Use fopen to generate a valid file identifier." "nextline = fgets(fid);"

How do I need to modify the program? Thank you~

Answer 1

[KSSV]

You are closing the file in the loop. close the file after the loop. I assume the below should work.

function read_datapattern(filename)
fid = fopen(filename,'rt');
if fid < 0
  error('error opening file %s\n\n',filename);
end
pattern = fgets(fid);
for n = 1:32767
  nextline = fgets(fid);
  pattern = strcat(pattern, nextline);
fprintf(pattern);
fprintf('\n');
end
fclose(fid);

[Zhonghao Liao]

Yes, that is work. Thank you~