Script for checking for installed applications

Question

I'm trying to write a script for ubuntu 10.0.4 to check for an application on my system. I want the script to see if the particular named application is installed, and if it is, if it needs updating. I also want the script to automatically install the app if it isn't installed, or update the application if it is installed. Like if i needed to install WINE or GIMP. I'm not sure how to structure the commands but I know I will use either apt-get, or yum to find the application.

Answer 1

You can combine these two pieces:

dpkg-query -W -f '${status} ${package} ${version}\n' |
sed -n 's/^install ok installed //p'

This will show the names of all installed packages, including their versions. If you don't need version numbers, omit the ${version} part.

Then, run apt-get update to get updated package lists, and:

/usr/lib/update-notifier/apt-check  -p

This will tell you the names of packages for which updates are available.

An idea would be (don't take this verbatim, I'm just providing an idea):

#!/bin/bash

$first_command > installed_packages
$second_command > packages_with_updates

if (grep $YOUR_PACKAGE installed_packages); then
   echo "Package is installed"
   if (grep $YOUR_PACKAGE packages_with_updates); then
      sudo apt-get -q -q update #apt-get runs in quiet mode to avoid lots of output
      echo "Update available for package"
      #Whatever you need to update the package here
   fi
else
   echo "Package not installed, installing..."
   #whatever you need to do to install here
fi