Is there a way to quickly check for the availability of security updates from the command line?
On my 12.04 system running
apt-get update fetches 20MB of data about available packages every time I run it, hitting many repositories along the way. Then I can use any of the methods described here to actually perform the update.
My question is just about detecting the availability of security updates (ie, not performing the actual upgrade using apt-get/aptitude/etc): is there a quick check that can be done from the command line that provides a yes-no answer the question "are there security updates available?". I would like to run that before running the lengthy
apt-get update + actual upgrade.
I suppose I don't need to download 20MB of data to know the answer to that every day.