In this article I will show you 4 ways to verify if a package is installed or not, in Debian, Ubuntu, Linux Mint, Knoppix and other Debian Based distros.
1. With aptitute:
$ aptitude show vim | grep -i state
State: installed
2-3. With dpkg:
$ dpkg -s vim | grep -i status
Status: install ok installed
$ dpkg -l | grep vim
ii vim 2:7.3.154+hg~74503f6ee649-2ubuntu3.1 Vi IMproved - enhanced vi editor
ii vim-common 2:7.3.154+hg~74503f6ee649-2ubuntu3.1 Vi IMproved - Common files
ii vim-runtime 2:7.3.154+hg~74503f6ee649-2ubuntu3.1 Vi IMproved - Runtime files
ii vim-tiny 2:7.3.154+hg~74503f6ee649-2ubuntu3.1 Vi IMproved - enhanced vi editor - compact version
4. With Apt package manager:
$ apt-cache policy vim | grep -i installed
Installed: 2:7.3.154+hg~74503f6ee649-2ubuntu3.1