This is a small how to on listing installed softwares in Linux Ubuntu OS. Some times we require to list softwares which are already installed so that we will not redo the same work by installing it once again.

Example1: To list installed softwares execute below command

dpkg –get-selections

Output(clipped):

xul-ext-ubufox                    install
xul-ext-unity                    install
xul-ext-webaccounts                install
xul-ext-websites-integration            install
xz-utils                    install
yelp                        install
yelp-xsl                    install
zeitgeist                    install
zeitgeist-core                    install
zeitgeist-datahub                install
zenity                        install
zenity-common                    install
zip                        install
zlib1g:amd64                    install
zlib1g:i386                    install

Example2: To count all installed softwares use below command which is modified version of above one.

	dpkg --get-selections | wc -l

Example3: To know the version and other details about installed package use below command

	aptitude show <package-name>

Example:

root@linuxnix:/home/surendra# aptitude show zip
Package: zip                             
State: installed
Automatically installed: no
Multi-Arch: foreign
Version: 3.0-8
Priority: optional
Section: utils
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Architecture: amd64
Uncompressed Size: 603 k
Depends: libbz2-1.0, libc6 (>= 2.14)
Recommends: unzip
Conflicts: zip
Provides: zip
Provided by: zip
Description: Archiver for .zip files
 This is InfoZIP's zip program. It produces files that are fully compatible with the popular PKZIP program; however, the command line options
 are not identical. In other words, the end result is the same, but the methods differ. 🙂 
 
 This version supports encryption.
Homepage: http://www.info-zip.org/Zip.html

Hope this helps some one who is in need to get details on the package installed in Ubuntu machine. 

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Mr Surendra Anne is from Vijayawada, Andhra Pradesh, India. He is a Linux/Open source supporter who believes in Hard work, A down to earth person, Likes to share knowledge with others, Loves dogs, Likes photography. He works as Devops Engineer with Taggle systems, an IOT automatic water metering company, Sydney . You can contact him at surendra (@) linuxnix dot com.