View source for Screen under systemd

Sometimes I want to run a process in [https://www.gnu.org/software/screen/ GNU Screen] out of [[systemd]], sometimes out of a user's session. This way, it gets started along with other services, I can monitor its status through standard systemd infrastructure, it gets restarted (or otherwise handled appropriately) on a crash or accidental kill/exit, but I can also come along at any time and monitor its (potentially tty-like) output and send it interactive input.

==rtorrent under Screen==
Here's my systemd unit for running [https://github.com/rakshasa/rtorrent rtorrent], a full-screen [[Ncurses]] application, under Screen in my user session:
<pre>
# /home/dank/.config/systemd/user/rtorrent.service
[Unit]
Description=rtorrent screen session
After=network.target

[Service]
Type=simple
ExecStart=/usr/bin/screen -L -DmS rtorrent /usr/bin/rtorrent
ExecStop=/usr/bin/screen -S rtorrent -X quit
NoNewPrivileges=yes
ProtectKernelTunables=yes
ProtectControlGroups=yes
RestrictNamespaces=yes
WorkingDirectory=/home/dank/var/lib/rtorrent
#RestrictAddressFamilies=AF_INET AF_INET6
#ProtectSystem=yes

[Install]
WantedBy=default.target
</pre>