If you manage the installed packages on your ubuntu server, you may know that the installation of a package that is already installed may lead in some circunstances to data loss. That's why is pretty useful to verify wheter a package has been already installed or not. This can be easily done in Ubuntu using the debian package manager (dbpk).
To verify if a package has been installed with a verbose output, you can use the following command:
dpkg -s <package name> | grep Status # example with the potrace package dpkg -s potrace | grep Status
For example, running the previous command will show the following output in the terminal (as long as potrace isn't installed):
dpkg-query: package 'potrace' is not installed and no information is available Use dpkg --info (= dpkg-deb --info) to examine archive files, and dpkg --contents (= dpkg-deb --contents) to list their contents.
If you feel uncomfortable with all the generated output, you can use even a shorter variant that generates less output:
dpkg -l <package name> # example with the potrace package dpkg -l potrace
Running the previous command on a system (assuming that potrace isn't installed) would generate the following output:
dpkg-query: no packages found matching potrace
Happy server management !