Hi, $INVOCATION_ID is quite a reliable source for this. I do not what if there are other behavior changes apart from forking you want to do but it is usually better to do those at a finer resolution than just a big check for systemd. First and foremost there are also other service managers which make forking unnecessary, the same hold for running your program in a container (e.g. Docker) - a cli flag might be a better option. If you want to use journald, check for it specifically using the socket or $JOURNAL_STREAM, for socket activation check $LISTEN_FDS, etc.
Cheers, Nils On Mon, Jun 30, 2025, 13:30 Stef Bon <stef...@gmail.com> wrote: > Hi, > > it's important for a program to detect it has been started by systemd. > For example it does not have to fork since it has already been forked. > > I've written a test script, which calls env, and there are a few > unique environment variables which are an indication it has been > started by systemd: SYSTEMD_EXEC_PID and INVOCATION_ID. > > Is it a good way to test these environment vars (to detect started by > systemd) or is there a better way? > > S. Bon >
