Trouble with permissions for fopen and textscan

I'm looking at reading in text data from a data I took in a .txt format from a data acquisition unit and I'm having trouble reading it into MatLab. The following is what my function looks like:

% 
function [ data0 ] = NIopen( filename )
fileID=fopen(filename);
data=textscan(fileID, '%s %s %s %s %s %s %s %s');
data=data(3);
data=data{1,1};
data=data(2:end);
data0=str2double(data(:));
fclose('all');
end

I'm looking at just getting the third column of data (date, time, data, date, time, data), but for some reason, I keep getting the following message referencing fopen() not working for some reason.

 NIopen('Combo_1_2_70.txt');

>>NIopen('Combo_1_2_70.txt');
??? Error using ==> textscan
Invalid file identifier.  Use fopen to generate a valid file identifier.

Error in ==> NIopen at 7
data=textscan(fileID, '%s %s %s %s %s %s %s %s');

And when that gets resolved (I change the permissions to 'r+'), textscan() spits out 8, 0x1 [] cells. This worked this morning and now it's not, leading me to wonder if it's a permissions issue, but I'm not sure how to proceed. Any help would be very much helpful!

Thanks!

Answer 1

[Image Analyst]

Try replacing this line

fileID=fopen(filename);

with this:

if ~exist(filename)
  errorMessage = sprintf('Error: file %s not found.  Click OK to exit.\n', filename);
  fprintf('%s\n', errorMessage);
  uiwait(warndlg(errorMessage));
  return;
end
fileID=fopen(filename)
fprintf('fileID = %d\n', fileID);

[Anuradha Bhattacharya]

Why does this 'Invalid permission' message arise at all? What does it mean?

[Walter Roberson]

Anuradha Bhattacharya, please post an exact copy of the error message. Also, try

[fileID, msg] = fopen(filename, 'rt');
if fileID < 0
  error('Failed to open file "%s" because "%s"', filename, msg);
end