Why did my fread suddenly stop working?

file = uigetfile('*.bin', 'select a binary file');

[fid, message] = fopen(file,'r');

% Read number of frames

NumberOfFrames = fread(fid, 1, 'int16');

I've had this code working for a couple of weeks now. I reinstalled matlab yesterday and took the night. When I returned today this code produced an error which it has not done before, namely:

Error using fread
Invalid file identifier. Use fopen to generate a valid file identifier.

I would appreaciate any help on the matter, or fixes if anyone has had this happening.

[KSSV]

What is value of fid? Probably problem is at fopen.

[Stian Hilstad]

The value of fid was -1

Answer 1

[Walter Roberson]

[filename, filedir] = uigetfile('*.bin', 'select a binary file');
if ~ischar(filename)
  return;
end
file = fullfile(filedir, filename);

[fid, message] = fopen( file, 'r');
if fid < 0
   error("failed to open file "%s" because "%s"', file, message);
end

[Stian Hilstad]

It worked, thank you! But could you give me any insight into what the error was and why it didn't occur before?

[Walter Roberson]

My guess is that you were asking to read a file in a different directory. Your code expected the file to be in your current directory.