Delete .deb files of Removed packages from apt-cache

apt-get autoclean deletes outdated .deb files from /var/cache/apt/archives directory which are no longer available or cannot be downloaded anymore.

whereas apt-get clean deletes each and every .deb file located in /var/cache/apt/archives directory.

I want to delete the .deb files of only those packages which are no longer installed, have been uninstalled or removed. How to do this?

APT relies on fcntl(2) locking; since ubuntu does not provide an fcntl lock command, you may use fcntl-lock utility for locking (a clone of Peter Anvin's flock command, slightly outdated, though).

#!/bin/bash

apt_cache=/var/cache/apt/archives

# Link: https://github.com/magnumripper/fcntl-lock
# fcntl-lock is a fcntl() clone of H. Peter Anvin's flock(1)
coproc LOCK {
    exec fcntl-lock \
    -x -w 3600 "$apt_cache/lock" -c 'echo true; exec cat'
}
read -ru ${LOCK[0]} || { \
    echo Failed to obtain a lock.
    exit 1
}

declare -a a=()
declare -A A=() B=()

# URL decode .deb filenames.
cd "$apt_cache"
for b in *.deb; do
    printf -v c %b "${b//%/\\x}"; A[$c]=$b
done

# You may use @(rc|ii) to add more Abbrev's
while read -r d e; do
    [[ $d = ii ]] && B[$e]=1
done < <( \
    dpkg-query \
        -Wf='${db:Status-Abbrev} ${Package}_${Version}_${Architecture}.deb\n' \
)

for f in "${!A[@]}"; do
    [[ ${B[$f]} = 1 ]] || \
        a+=("$apt_cache/${A[$f]}")
done
((${#a[@]} > 0)) && \
    printf %s\\0 "${a[@]}" | xargs -0 rm -v || exit 0

# echo Success | ts >> /var/log/apt-archive-clean.log

If you want to automate, I think using systemd.path works best.

apt-archive-clean.path

[Unit]
Description=APT Archive Cleanup

[Path]
PathChanged=/var/cache/apt/archives/lock

[Install]
WantedBy=multi-user.target

apt-archive-clean.service

[Unit]  
Description=APT Archive cleanup  
  
[Service]  
Type=simple  
ExecStart=/opt/bin/apt-archive-clean.sh