List available updates but do not install them

Question

I want my cron-run reporting script to notify me in case there are updates for my packages. Is the a way to make apt-get give me the list of available updates but don't do anything more?

Answer 1

The -u switch shows a list of packages that are available for upgrade:

# apt-get -u upgrade

From the apt-get man page:

-u
--show-upgraded  Show upgraded packages; Print out a list of all packages that are to be upgraded. Configuration Item: APT::Get::Show-Upgraded.

Answer 2

You can run

aptitude -F%p --disable-columns search ~U

or the undocumented

/usr/lib/update-notifier/apt-check -p; echo

Another method using an apt-get simulation:

apt-get -s dist-upgrade | awk '/^Inst/ { print $2 }'

Answer 3

Take a look at package "apticron":

apticron - Simple tool to mail about pending package updates

http://packages.debian.org/squeeze/apticron

Answer 4

apt-get --just-print upgrade

Is not read that easily, below is a perl one liner to parse apt-get's output:

apt-get --just-print upgrade 2>&1 | perl -ne 'if (/Inst\s([\w,\-,\d,\.,~,:,\+]+)\s\[([\w,\-,\d,\.,~,:,\+]+)\]\s\(([\w,\-,\d,\.,~,:,\+]+)\)? /i) {print "PROGRAM: $1 INSTALLED: $2 AVAILABLE: $3\n"}'

This should output something like:

PROGRAM: grub-pc INSTALLED: 1.99-21ubuntu3.1 AVAILABLE: 1.99-21ubuntu3.9

Hopefully it will help someone else,