.config/systemd/user/pacman-packages.service

[Unit]
# REQUIRES: https://github.com/speziato/dotfiles/.local/bin/pacman-packages.sh
Description=Get the list of explicitly installed packages with pacman and save it in a file
After=local-fs.target
After=network.target
#After=XXX

[Service]
ExecStart=%h/.local/bin/pacman-packages.sh build
RemainAfterExit=no
Type=oneshot

[Install]
WantedBy=default.target