How to show the number of installed packages

Question

What is the Debian equivalent of Fedora's yum list installed | grep wc --lines?

Answer 1

According to this thread:

To list installed packages:

dpkg --list | wc --lines

To see if a package is installed:

dpkg --list | grep package

Answer 2

dpkg -l | grep -c '^ii'

There are subtle variants like dpkg -l | grep -c '^?i' if you want to include packages that are installed but whose removal you've requested. Another way is

aptitude search '~i' |wc -l

You can even poke directly into the dpkg database:

sh -c 'set /var/lib/dpkg/info/*; echo $#'

This one includes packages that are not installed but that have configuration files left over; you can list these with dpkg -l | grep '^rc'.

Answer 3

dpkg -l is nice but I actually find myself using apt-show-versions (not installed by default on Debian; install the package of the same name) a lot instead, especially when I want to process the output further (dpkg tries to be too clever with line wrapping).

Answer 4

Synaptic, a GUI package manager, displays the count at the bottom of its main window.

Answer 5

What I've been using is:

dpkg --get-selections | wc --lines

This will give you the number of installed packages.

If you want to find if a particular package is installed, use:

dpkg --get-selections | grep <package>

I believe that this will solve Gilles' complaint about including other, non-installed packages.