Compiled application does not write to diary log file

Hi all,

I have created a project using app designer and a number of functions. To keep track of how the calculation routes through the various functions I save comments in a log file using the diary() function and many fprintf() functions (see simplified example code below). This all works perfectly when run through matlab.

However, when I run a compiled version of the project, the log file is completely empty, even though the log file itself is created. (other files are also created/saved correctly).

I assume it's because there is no command window... for fprintf() to write to...? The same happens on my colleagues system.

Is there a way around this? Or do I need to write a dedicated logging function?

TIA, Mark.

R2019b

function mlappGUI()
    main()
end

function main()
    diary('c:\MatLab\logFile.log') %starts the log file
        sub1()
        sub2()
    diary off
end

function sub1()
    fprintf('subFunction1 : log file comment\n');
end

function sub2()
    fprintf('subFunction2 : log file comment\n');
end

[Dani]

If I compile your example (mcc -e mlappGUI.m) und run the exe then I do get the logfile with all its entries. This is with 2020a.

But I have come across this problem before. I was relying on diary for logging warnings and errors in my deployed applications (yes, lazy, but efficient, saves you adding endless try-catch statements) and with the introduction of 2019b it stopped working. The problem was that it did not stop to work entierly, so simple test cases worked for me but my full application it did not. Difficult to debug. So, I'm not sure if your test script is one of the simple cases or if in 2020a this started working properly again.

Answer 1

[Fangjun Jiang]

I think you are right. The cause is that there is no Command Window in your compiled app.

I would suggest writing to a specific file. Use fid=fopen() to create a FID and then fprintf(fid,'log text')

You can switch to Command Window when forcing fid to be 1.

fprintf(1,'abc\n') is the same as display('abc')

[MC]

Hi Fangjun Jiang,

Thanks for the response.

I have reworked it to look something like this and used a single global variable as I don't pass lots of data into some of the smaller functions.

function main()
    global logID
    logID = fopen('C:\matlab\Log.log');
        fprintf(logID,'main: blah %i\n',0);
        sub1()
    fclose(logID)
end

function sub1()
    global logID
    fprintf(logID,'sub1: blah %i\n',1);
end

The only problem is that fprintf() doesn't output to the command window (which is useful for development).

A possible solution may be to create a dedicated logging function which outputs to both:

function main()
	global logID
	logID = fopen('C:\matlab\Log.log');
		logEntry(sprintf('main: blah %i\n',0))
		sub1()
	fclose(logID)
end

function sub1()
	logEntry(sprintf('sub1: blah %i\n',1))
end

function logEntry(txt)
	global logID
	fprintf(txt); % display in command window
	fprintf(logID,txt); % save to log file.
end

[Fangjun Jiang]

When you debug during development, force logID to be 1 somewhere then it will print to the Command Window. Run diary() outside of your app to save the log into a file.

[MC]

Good tip. thanks.