To check if a given package is installed in Debian / Ubuntu, type
dpkg -s <package-name>
To get a neater output use dpkg-query which accepts wildcards as well.
dpkg-query -l <package-name>
In Redhat / Fedora / CentOS use the following command
rpm -qa | grep <package-name> # no output, package not installed
# to display list of all installed packages
rpm -qa
rpm -qa | less
Posted by Sandheep to Sandheep's deck (2013-05-03 14:17)