What happens in response to fprintf commands when a deployed app is created using deploytool?

I am creating an App for others to use the matlab code, using deploytool. I have a couple of questions.

1. What happens if I am using the fprintf commands since there is no MATLAB window to print in response to this command?

2. My code runs fine in the MATLAB environment. However, when I run the app created by deploytool, it bombs with no indication of where it did so? How can I debug this error since debug flags cannot be used here?

Answer 1

[Benjamin Kraus]

You can specify a file identifier (created using fopen) as the first input to fprintf, which will send the output to a file. If you don't specify the file, then fprintf should send all it's output to "standard out", which should be the command line you used to launch your App. If you started the App by double-clicking the executable, I don't believe the output is sent anywhere, so if you want to capture that output you need to start your App from a terminal or command window (the details depends on your operating system).

[Ranjan Sonalkar]

Ben Thanks for your solution. Another related question, if you do not mind. I have a pause in the code to allow the user to zoom into a drawn figure. Then I would like to resume the program. In normal running any key press resumes it. However, in the deployed application, (which I start from a CMD window, so the I/O from the code should go to the CMD window) the program pauses, however, I cannot get it to resume. The CMD window appears to be locked and the keyboard entries are ignored.

[Walter Roberson]

No, input data files that come with the installation are always in ctfroot() or a subdirectory of that. The default output directory will be ctfroot().

If you want the user to be able to customize input and output locations then you need to build that into the executable.

[Walter Roberson]

Ranjan Sonalkar: I noticed you edited your comment. I see your question about the pause now, but I do not know whether that is something that you dealt with months ago, or if that is a new question that you edited into place ?

[Ranjan Sonalkar]

It is related to the original question regarding how to interact with the App. I want the app to display instructions, so the user can act accordingly. I start the app from CMD window and I am still not getting the disp command in the code to display the instructions in the window. I also want the app to pause the program to allow the user to zoom into a figure. Then the user should be able to press any key (as you can do when running MATLAB code directly) to resume the program. I inserted pause("on") in the code, so the code pauses. But I cannot get it to resume. That is, even if I press any key, the code does not resume as it is supposed to.

[Walter Roberson]

Are you asking to create a "console program" or an "application" ?

Answer 2

[Ranjan Sonalkar]

I don't know the difference. I use deploytool to create the deliverable APP.

[Walter Roberson]

An "application" is something like MATLAB itself, in that when the user launches it, it starts up its own graphics and runs independently.

A "console program" might have graphics but it relies upon starting up a command shell and executing from the command shell. System error messages and stderr (standard error output) are sent to the command shell.

[Ranjan Sonalkar]

I need the program to send some output to the CMD window after I start the program from the CMD window. The answer by Ben Kraus suggested to start the program from the CMD window and then use fprintf without specifying a file output. I did that but I still do not get the fprintf output text in the CMD window.

[Walter Roberson]

I do not use deploytool myself, but it appears to me that if you ask to use the application compiler, and go to the Settings icon, then there is a field for addition settings to be passed to MCC. If you put

-m

there, then I think it will create a console program. But possibly I am misreading and you might need -e instead of -m

https://www.mathworks.com/help/compiler/compile-a-standalone-application-from-the-command-line.html