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

It seems that nowadays apt-get has an option --no-upgrade that just does what the OP wants:

--no-upgrade Do not upgrade packages. When used in conjunction with install, no-upgrade will prevent packages listed from being upgraded if they are already installed.

Manpage from https://linux.die.net/man/8/apt-get

Therefore you can use

apt-get install --no-upgrade package

and package will be installed only if it's not.