How do I observe and control a macOS update using `softwareupdate`? I made the mistake (don't ask) of entering

softwareupdate -ia --verbose


in Terminal, which is now stuck doing — I don't know what:

Software Update Tool

Finding available software

Downloading Command Line Tools (macOS Mojave version 10.14) for Xcode
Downloading macOS 10.14.4 Update
Downloaded Command Line Tools (macOS Mojave version 10.14) for Xcode
Downloaded macOS 10.14.4 Update
Installing Command Line Tools (macOS Mojave version 10.14) for Xcode, macOS 10.14.4 Update
Done with Command Line Tools (macOS Mojave version 10.14) for Xcode


and attempts to stop it with ^C result in 

Cannot cancel updates after installation has started.


I have no progress indictor or feedback, and this has been going on for hours and softwareupdate --dump-state shows no entries (except for running dump-state) for quite some time.

How do I check the status of a softwareupdate installation, and how do I abort it if it isn't stopping or completing on its own?
Out of frustration I simply tried
softwareupdate --install --all

in a new Terminal window, which unstuck the instance of softwareupdate running on the other original window. This seems to have resolved the issue completely.