This is useful for running programs unattended but not fully in background. The main effect is to convert any message boxes which would otherwise require user input to trace messages in the System Messages window or on the screen.
Beginning with A-Shell 7.0.1778 of October 2025, the -ua switch has an additional side effect under Linux: it allows allow background jobs to sit at input prompts without aborting. Normally a process in background will terminate when it tries to input if it doesn't have a real terminal and there is no piped input available, which normally makes sense. But in some cases, it is useful to be able to launch a background task and let it wait for input to be forced to it via the FORCE command. In particular, this technique is used by ADB when debugging a process running in a background task launched by ADB itself.
