Read user input in app generated by jpackage

Question

I am using jpackage to convert a Java application into an executable .app file.

When running on macOS, as shown below, the application cannot read user input.

open -n /Applications/MyApp.app

The application can read user input if it is run as

open -n /Applications/MyApp.app/Contents/MacOS/MyApp.app

This is the code to read user input (using batch script is not applicable here)

BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
while (true) {
   String line = reader.readLine();
   // process the string line here
}

What needs to be done to read user input when launching an application using open -n /Applications/MyApp.app (or another convenient command) ?

You should ask yourself what exactly you are trying to read. — soundflix
– soundflix, Commented Jul 25 at 19:17

TITKOV · Accepted Answer · 2025-07-23 21:32:39Z

1

Use Terminal to Launch the Executable

Instead of using open, you can directly invoke the executable file within the app bundle: bash

/Applications/MyApp.app/Contents/MacOS/MyApp

This ensures the application attaches to the terminal and can read user input. i hope*

answered Jul 23 at 21:32

TITKOV

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4 Comments

Evgeny Jul 23 at 21:44

This works, the app is connected to the OS terminal and allows reading user input. Is there a way to collect user input when the app is launched, by clicking on its icon in the Dock or by running it as /Applications/MyApp.app?

TITKOV Aug 31 at 12:56

On macOS, when you start a .app via Finder / Dock / open, it launches as a GUI app with no controlling terminal. That means stdin is not attached to a TTY (often /dev/null), so readLine() will block and you won’t be able to read from the keyboard. There isn’t a flag in jpackage that makes a GUI app suddenly get a terminal.

TITKOV Aug 31 at 12:57

1) osascript -e 'tell application "Terminal" do script "/Applications/MyApp.app/Contents/MacOS/MyApp" activate end tell' 2) Create MyApp.command (make it executable with chmod +x) anywhere (e.g., alongside the .app) with: #!/bin/bash /Applications/MyApp.app/Contents/MacOS/MyApp read -n 1 -s -p "Press any key to close..." Double-clicking MyApp.command opens a Terminal window and runs the app.

TITKOV Aug 31 at 12:57

If your app must be launched like a normal Mac app (Finder/Dock), don’t use stdin. Replace the BufferedReader code with a small Swing/JavaFX (or even AWT) dialog to capture inputt

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