Bug 64614 - make sd_journal_next after sd_journal_seek_tail return 0 and enhance documentation
Summary: make sd_journal_next after sd_journal_seek_tail return 0 and enhance document...
Status: NEW
Alias: None
Product: systemd
Classification: Unclassified
Component: general (show other bugs)
Version: unspecified
Hardware: Other All
: medium normal
Assignee: systemd-bugs
QA Contact: systemd-bugs
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Reported: 2013-05-15 07:05 UTC by Marius Vollmer
Modified: 2015-09-08 21:47 UTC (History)
4 users (show)

See Also:
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Attachments
Test program. (1014 bytes, text/plain)
2013-05-15 07:05 UTC, Marius Vollmer
Details

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Description Marius Vollmer 2013-05-15 07:05:38 UTC
Created attachment 79325 [details]
Test program.

From the documentation, one might understand that sd_journal_seek_tail move to the last entry and that a subsequent sd_journal_next would access that entry.
(Because it is worded very much like the docs for sd_journal_seek_head, which works that way.)

In fact, sd_journal_seek_tail seems to move to just _after_ the last entry, and one needs to use sd_journal_previous to access it.  I think this should be documented more clearly.

What's worse is that if does call sd_journal_next after sd_journal_seek_tail, this is successful and will access random entries.  Instead, I would expect sd_journal_next to return 0 (or an error).  The attached program demonstrates this.

I might try to provide some patches (docs and code), but with low priority.
Comment 1 Marius Vollmer 2013-06-10 06:43:54 UTC
Not that even with improved documentation, it would still be very good to have sd_journal_next after sd_journal_seek_tail return an error instead of succeeding and moving to a random entry.
Comment 2 Zbigniew Jedrzejewski-Szmek 2013-06-10 14:36:38 UTC
(In reply to comment #1)
> Not that even with improved documentation, it would still be very good to
> have sd_journal_next after sd_journal_seek_tail return an error instead of
> succeeding and moving to a random entry.

You're right, I somehow missed the part about random results...

It would be great if you turned you test program directly into a test that we can include in systemd. I did something like that with your other program (http://cgit.freedesktop.org/systemd/systemd/commit/?id=7a050b54).

I'm pretty sure that sd_journal_next after sd_journal_seek_tail should return 0.
Comment 3 Daurnimator 2014-10-16 15:16:18 UTC
I ran into this bug. Mailing list thread: http://lists.freedesktop.org/archives/systemd-devel/2014-October/023916.html


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