MATLAB: Error in .exe but not in .m file

.exe problemMATLAB Compiler

Here is my program, reading a folder(let's say five .txt file in this folder)and the information where in the txt file will display on the Textbox,my program works well in .m file, but once I convert to .exe file, the error occurred on reading function (fid = -1, 'Invalid file identifier'), so I had to check this problem, and I found that if I didn't 'add path' my test folder to the working environment, the same problem occurred again…below shows the code of the reading function:
if true
  % code
==================================================
inputData = dir(fullfile(inputPath,'*.txt'));
  fileLength = length(inputData);
  for i = 1:fileLength
      fileName = inputData(i).name;
      fid = fopen(fileName, 'rt');
        %%%%%%%%%%%%test %%%%%%%%%%%%%%
        display(num2str(fid));
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
end

Best Answer

Use an absolute path:
inputData = dir(fullfile(inputPath,'*.txt'));
fileLength = length(inputData);
for i = 1:fileLength
    fileName = inputData(i).name;
    file     = fullfile(inputPath, fileName);  % Absolute path
    fid      = fopen(file, 'rt');
    if fid == -1, error('Cannot open file: %s', file); end
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