Support of non systemd linux systems.

[zen2]

My system is not using systemd and so NSL is not launched as a daemon and produce errors when looking for systemctl command.
I've commented systemd part of the code and I'm able to install launchers.
I can scan games too by using myNSLGameScanner.py but I need to restart steam in order to see new games (I don't know if this restart is required on functional NSL installation).

So it can be really good to detect other classical /etc/init.d system and ideally to have a script that accept start/stop/restart in order that NSL can be easily integrated in any kind of init system.

[moraroy]

@zen2 ah thanks for the heads up, I didn't realize that would be an issue! I'll try my best to fix that for you, so essentially since there is no service file being ran, you're basically just running the .py manually correct? If I can find a way to not have a service file that would be better in my opinion.

[zen2]

@moraroy the classical way is to make a script autonomous from system with optionally a background option command and provide optionality systemd or init.d files separately. In my case I can write my own init.d one if the script works on itself.

Most of linux distro package maintainers write needed init.d script or systemd init files to launch daemon process.
So it means your script have to be independent from it.
It is the init system that take care to start/stop/restart and keep it in background the process/script.
Usually the init system create a pid file to track if the process have been already start and is running.
Note that the process can create his own pid file on his own if needed and so the init.d system will use it.

About background option:
It means when you launch the script normally from a terminal it will be launched in foreground by taking over the terminal and use it for stdout/stderr.
With an option like --background/-b the script can detach from terminal and run in background.

About daemon exit:
If you need to clean up some temporary files or execute specific actions before the daemon exits you need to intercept signals that will be send by the init system to kill the daemon. Usually init system send a SIGTERM signal to ask daemon to terminate properly then a SIGKILL signal to kill it anyway after a timeout in case the process doesn't terminate.

Basic example in bash:

#!/bin/bash

myname="$(basename $0)"
mypath="$(dirname $0)"
mylog="/tmp/${myname}.log"

# Relaunch script in background and exit
if [ "$1" = "-b" ]; then
  nohup "$mypath/$myname" &> "$mylog" &
  pid=$!
  echo "$myname is running now in background."
  echo "Command to terminate the background process: kill -15 $pid"
  exit 0
else
  echo "Launch me with -b option to make me running in background."
fi

# function to clean up before exiting
exit_on_trap() {
  echo "Execute actions to clean up before exiting"
  rm "$mylog"
  exit 0
}

# intercept exit signal to exit properly
trap exit_on_trap SIGTERM SIGQUIT

# Daemon main loop
while true; do
  sleep 1
  echo "I'm alive"
done

In python, take a look to:

• daemonize: https://github.com/thesharp/daemonize/
• python-daemon: https://pagure.io/python-daemon/