Check if an apt-get package is installed and then install it if it's not on Linux

Question

I\'m working on a Ubuntu system and currently this is what I\'m doing:

if ! which command > /dev/null; then
   echo -e \"Command not found! Install? (y/n)         


        

Answer 1

To check if packagename was installed, type:

dpkg -s <packagename>

You can also use dpkg-query that has a neater output for your purpose, and accepts wild cards, too.

dpkg-query -l <packagename>

To find what package owns the command, try:

dpkg -S `which <command>`

For further details, see article Find out if package is installed in Linux and dpkg cheat sheet.

Answer 2

I've found all solutions above can produce a false positive if a package is installed and then removed yet the installation package remains on the system.

To replicate: Install package apt-get install curl
Remove package apt-get remove curl

Now test above answers.

The following command seems to solve this condition:
dpkg-query -W -f='${Status}\n' curl | head -n1 | awk '{print $3;}' | grep -q '^installed$'

This will result in a definitive installed or not-installed

Answer 3

For Ubuntu, apt provides a fairly decent way to do this. Below is an example for google chrome:

apt -qq list google-chrome-stable 2>/dev/null | grep -qE "(installed|upgradeable)" || apt-get install google-chrome-stable

I'm redirecting error output to null because apt warns against using its "unstable cli". I suspect list package is stable so I think it's ok to throw this warning away. The -qq makes apt super quiet.

Answer 4

In Bash:

PKG="emacs"
dpkg-query -l $PKG > /dev/null || sudo apt install $PKG

Note that you can have a string with several packages in PKG.

Answer 5

I use the following way:

which mySQL 2>&1|tee 1> /dev/null
  if [[ "$?" == 0 ]]; then
                echo -e "\e[42m MySQL already installed. Moving on...\e[0m"
        else
        sudo apt-get install -y mysql-server
                if [[ "$?" == 0 ]]; then
                        echo -e "\e[42mMy SQL installed\e[0m"
                else
                        echo -e "\e[42Installation failed\e[0m"
                fi
        fi

Answer 6

To be a little more explicit, here's a bit of bash script that checks for a package and installs it if required. Of course, you can do other things upon finding that the package is missing, such as simply exiting with an error code.

REQUIRED_PKG="some-package"
PKG_OK=$(dpkg-query -W --showformat='${Status}\n' $REQUIRED_PKG|grep "install ok installed")
echo Checking for $REQUIRED_PKG: $PKG_OK
if [ "" = "$PKG_OK" ]; then
  echo "No $REQUIRED_PKG. Setting up $REQUIRED_PKG."
  sudo apt-get --yes install $REQUIRED_PKG 
fi

If the script runs within a GUI (e.g. it is a Nautilus script), you'll probably want to replace the 'sudo' invocation with a 'gksudo' one.