Why using "fullfile" inside "fopen" gives error but "uigetfile" along with "fopen" works fine?

I am trying to use: Method-1

fullName1 = fullfile(filepath, filename);
[fid1, msg1] = fopen(fullName1 , 'r', 'ieee-le');

Method-1 yields:

fid1 = -1 (file was NOT found).

I have also tried doing this as follows: Method-2

[fName, fPath] = uigetfile(*.*);
fullName2 = [fPath, fName];
[fid2, msg2 = fopen(fullName, 'r', 'ieee-le');

Method-2 yields:

fid2 = 3 (file was opened).

This is so surprising! The first method could not find the file at all while the second could. So, I compared the strings fullName1 and fullName2:

strcmp(fullName1, fullName2)  --> This yields 0; 
=> fullName1 and fullName2 are different!

If someone could kindly explain why this is happening and what could fix this, that will help me a lot. My ultimate goal is to use fileName1 inside fopen. (i.e. use method-1)

Thanks.

Note: The folder where the data files are kept has also been added to the search path in MATLAB. Also, I have already looked at all the following sites--

1. https://www.mathworks.com/help/matlab/ref/fullfile.html
2. https://www.mathworks.com/help/matlab/ref/fopen.html
3. https://www.mathworks.com/matlabcentral/newsreader/view_thread/88964
4. https://www.mathworks.com/matlabcentral/answers/73662-open-multiple-files-with-fopen
5. http://stackoverflow.com/questions/10606373/what-causes-an-invalid-file-identifier-in-matlab

[Guillaume]

"The folder where the data files are kept has also been added to the search path"

That won't make any difference. Since you're using the full path of the file the folder doesn't need (and shouldn't) be in matlab search path.

I can't see anywhere in your question why fullname1 and fullname2 should be the same unless filepath and filename in method 1 are identical to the file you select with method2. Clearly, they're not as your strcmp test demonstrates.

[Adam]

This is an issue of how you define 'filename' and 'filepath'. If you pasted one of them in from Windows Explorer or somewhere then you probably have one of the invisible characters that Walter's answer mentions included.

I'm not sure what exactly causes this to happen. I've had it once or twice before, but usually copying and pasting a name works fine. However, it may just be that if you paste over slightly too much to do the copy you will pick up some hidden character in your name too.

You can run an isdir test on your filepath variable to check if it is found as a directory before adding your filename to it.

[Steven Lord]

You called fopen with two outputs in the first call, the one that failed. What were the contents of that second output? That should be a message from the system indicating why fopen was unable to open the file.

[Sugato]

After diagnosing a little bit more, I realized that there was a minor error in the filename ( variable: filename) that was provided by hardcoding it. The uigetfile on the other hand was able to pick the file name and path correctly and that's why it was working. Thank you very much for your time and suggestions.

@Adam: Thanks for pointing out where the error could be.

Answer 1

[Jan]

There can be other reasons for a failing fopen:

• The number of open files exceeds the limit defined by the operating system. See fopen('all')
• The file is opened for writing from anywhere else.
• Typos or invisible characters in the file name.

Answer 2

[Walter Roberson]

Are the strings the same length?

Is it possible that there is a non-printing character in the file name? Compare double(fullName1) to double(fullName2)