Find Packages Installed with apt-get

#!/bin/bash

# apt-list - A script to show packages installed with apt-get
#
# Usage: apt-list <installed|removed|kept>
#
# G+ Post: https://plus.google.com/+JessiBaughman/posts/7USUQfh3y7y
# Created by: Jessi A. Baughman
# Last Modified: 2018-09-06

if [[ $1 == "installed" ]];then
    awk '$0 ~ "install " {if ($4 != "install" && $4 != "-y" ) print $4}' /var/log/apt/history.log | awk '!x[$0]++' | sort
elif [[ $1 == "removed" ]];then
    awk '$0 ~ "remove " {if ($4 != "remove") print $4}' /var/log/apt/history.log | awk '!x[$0]++' | sort
elif [[ $1 == "kept" ]];then
    awk '$0 ~ "install " {if ($4 != "install" && $4 != "-y") print $4} $0 ~ "remove " {if ($4 != "remove") print $4}' /var/log/apt/history.log | awk '{!seen[$0]++};END{for(i in seen) if(seen[i]==1)print i}' | sort
else
    echo
    echo "Usage: apt-list <installed|removed|kept>"
    echo
fi