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

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Sugato 2017-1-12

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https://ww2.mathworks.cn/matlabcentral/answers/320077-why-using-fullfile-inside-fopen-gives-error-but-uigetfile-along-with-fopen-works-fine

评论： Sugato 2017-1-12

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--

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Steven Lord 2017-1-12

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 2017-1-12

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.

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Answer 1

Jan 2017-1-12

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https://ww2.mathworks.cn/matlabcentral/answers/320077-why-using-fullfile-inside-fopen-gives-error-but-uigetfile-along-with-fopen-works-fine#answer_250338

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.