Does systemd expose any unit-file-parsing functionality?

Tom Lane tgl at
Thu Mar 22 00:39:58 UTC 2012

Lennart Poettering <mzerqung at> writes:
> On Sat, 17.03.12 11:41, Tom Lane (tgl at wrote:
>> Tomasz Torcz <tomek at> writes:
>>> You can try
>>> systemctl show -p Environment <unit>

>> [ experiments with that ... ]  Hm, the output format seems pretty
>> ill-designed, but I guess I can pick it apart with some careful
>> sed'ing.  Better than trying to handle .include for myself, anyway.
>> Thanks for the suggestion!

> Hmm, what are you mising in the output format? We are always interested
> in suggestions for imprvoement.

The case that I was interested in was for postgresql, which needs to
scrape the PGPORT port number setting and the PGDATA data directory path
out of postgresql.service.  Assuming that somebody has overridden the
PGPORT setting by using a custom service file that .include's the
standard one, what I find "systemctl show" producing is a line like

	Environment=PGPORT=5432 PGDATA=/var/lib/pgsql/data PGPORT=5433

So I have to pick this apart, understanding that later entries override
earlier ones.  And the really nasty problem with it is that the layout
is simply broken by environment variable names or values that contain
spaces.  I don't mind so much needing to implement a "take the last
match" rule, but it'd be nice if I didn't have to tell people they can't
use a PGDATA path that includes spaces.  I don't have an immediate
proposal for making it better though.

> Note that this command will not show you the environment inherited by
> the PID 1 or any other env that is passed on that is not explicitly
> configured in the unit files.

No, that's not a problem, I just need to know what's configured in the
unit file(s).

BTW, while I'm thinking about it: I found in testing that any editing
of the on-disk files was reflected immediately in "systemctl show"'s
output.  Which was exactly what I wanted, but it surprised me quite a
bit --- I was expecting that what this command shows is systemd's
internal state and thus I'd have to do daemon-reload to make it update
after an edit.  Can I expect that that behavior will persist, or am I
relying on something that's going to change?

			regards, tom lane

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