How can I know which file identifiers correspond to open files?

I have opened a file using FOPEN and processed it. A few lines of code later, there was an error, and the file wasn't closed properly.

I would like to know which file identifiers correspond to open files so I can close them using FCLOSE.

Answer 1

[MathWorks Support Team]

To see the list of identifiers of all open files you can use the following command:

fids = fopen('all')

To see the file names which correspond to those file identifiers you can use the following command:

filenames = arrayfun(@fopen, fids, 'UniformOutput', 0)

Finally, if you just want to close all open files you can use the following command:

fclose('all')

Answer 2

[Josh Kahn]

Also, if you want to avoid this, you can now use a cleanup object to close the file when the function is done (error or normal) similar to a try/catch.

For more information, see:

https://www.mathworks.com/help/matlab/ref/oncleanup.html

function myFunction
    fid = fopen('myFile.txt', 'w')
    cleanup = onCleanup(@() fclose(fid));
    
    fprintf(fid, 'hello!');
end

equivalent to:

function myFunction
    fid = fopen('myFile.txt', 'w')
    
    try
        fprintf(fid, 'hello!');
        fclose(fid);
    catch ME
        fclose(fid);
        rethrow(ME);
    end
end