[systemd-devel] Return codes of systemctl (status)

[Cecil Westerhof]

The man page of systemctl says:
On success, 0 is returned, a non-zero failure code otherwise.

When I do a systemctl status on a service that is not running I get a 3.
What other values can be returned and where do I find those?

[Ryan Gonzalez]

I believe the errors are based on errno:
http://www.virtsync.com/c-error-codes-include-errno

Return status 3 -> ESRCH -> No such process

Post by Cecil Westerhof
On success, 0 is returned, a non-zero failure code otherwise.
When I do a systemctl status on a service that is not running I get a 3.
What other values can be returned and where do I find those?
--
Cecil Westerhof
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[Cecil Westerhof]

I believe the errors are based on errno: http://www.virtsync.com
/c-error-codes-include-errno
Return status 3 -> ESRCH -> No such process

Thanks I will look into that.


I think it is not completely correct. For example if I do:
systemctl status dummy

This gives as description:
Unit dummy.service could not be found.

And the error code that is returned is 4.
I would not say that a non existing service is an interrupted service call.
I would find 22 (invalid argument) more logical. But it all depends how you
interpret things.

Post by Cecil Westerhof
On success, 0 is returned, a non-zero failure code otherwise.
When I do a systemctl status on a service that is not running I get a 3.
What other values can be returned and where do I find those?

[Dave Reisner]

    On success, 0 is returned, a non-zero failure code otherwise.
When I do a systemctl status on a service that is not running I get a 3.
What other values can be returned and where do I find those?

I believe exit codes are meant to conform to LSB specs:

http://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/iniscrptact.html

In general, I'd suggest not depending on the specific values, but
instead using a more appropriate verb. For example, if you want to
know that a service is running, is 'systemctl is-active'.

dR

[Filipe Brandenburger]

Post by Dave Reisner

Post by Cecil Westerhof
On success, 0 is returned, a non-zero failure code otherwise.
When I do a systemctl status on a service that is not running I get a 3.
What other values can be returned and where do I find those?

http://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/iniscrptact.html

Yes, that is correct.

See comments and enum here:
https://github.com/systemd/systemd/blob/v239/src/systemctl/systemctl.c#L80

Post by Dave Reisner
In general, I'd suggest not depending on the specific values, but
instead using a more appropriate verb.

Agreed. In particular, man page for systemctl simply says "on success,
0 is returned, a non-zero failure code otherwise" for exit status. In
other words, the specific non-zero exit codes are undocumented, so
shouldn't be relied upon.

Cheers,
Filipe

[Cecil Westerhof]

Post by Filipe Brandenburger
Agreed. In particular, man page for systemctl simply says "on success,
0 is returned, a non-zero failure code otherwise" for exit status. In
other words, the specific non-zero exit codes are undocumented, so
shouldn't be relied upon.

Personally I would say that when asking the status of a non running service
is not a failure, but that does return a 3. So I have to catch that.

[Cecil Westerhof]

Post by Dave Reisner

Post by Cecil Westerhof
On success, 0 is returned, a non-zero failure code otherwise.
When I do a systemctl status on a service that is not running I get a 3.
What other values can be returned and where do I find those?

http://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/iniscrptact.html

That is quite an interesting bit of info. :-D

Post by Dave Reisner
In general, I'd suggest not depending on the specific values, but
instead using a more appropriate verb. For example, if you want to
know that a service is running, is 'systemctl is-active'.

The problem is that I use the commands from Tcl. I use the output, but when
using exec Tcl has 'a problem' with non zero codes. When I ask the status
of a service it can return a 0, 3, or 4. When returning a 3 that is not a
real error and I should inhibit the throw. If it is a 4 (service does not
exist) it is a real error and I should let the throw be fired.

[Lennart Poettering]

Post by Dave Reisner

    On success, 0 is returned, a non-zero failure code otherwise.
When I do a systemctl status on a service that is not running I get a 3.
What other values can be returned and where do I find those?

http://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/iniscrptact.html
In general, I'd suggest not depending on the specific values, but
instead using a more appropriate verb. For example, if you want to
know that a service is running, is 'systemctl is-active'.

This is correct. This is supposed to match LSB status exit codes, but
the mapping is a bit skewed due to different semantics.

In general we return 0 on success, non-zero otherwise, but "systemctl
status" (and a few verbs like it) do this differently to match LSB. We
should probably document that better. I filed a bug requesting this
now, so that we keep track of this.

https://github.com/systemd/systemd/issues/10056

Lennart