If using an OS X operating system most things are done with a GUI. However there are a lot of things under the hood one can do from command line. Lately I have been searching for a way to update the system and installed applications without using the App Store GUI. The command is called softwareupdate

Usage: softwareupdate <mode> [<args> ...]

** Catalog Management:
    --set-catalog <URL> Set the new catalog URL (requires privileges)
    --clear-catalog     Clear the catalog URL back to defaults (requires privileges)

** Manage Updates:
    -l | --list     List all appropriate update labels
    -d | --download     Download Only
    -i | --install      Install
        <label> ... specific updates
        -a | --all      All appropriate updates
        -r | --recommended  Only recommended updates

    --ignore <label> ...    Ignore specific updates
    --reset-ignored     Clear all ignored updates
    --schedule (on | off)   Set automatic checking

-v | --verbose  Enable verbose output
-h | --help Print this help

The following command will list all application that need to be updated

sudo softwareupdate --list 

This way it is possible to get updates for installed applications, it is not possible to install new applications.