Dear Maintainer,

I've tried to use faketime to build something reproducibly, by using the git
commit time.
Git offers shortcuts for the formats "iso" (e.g. "2019-09-06 03:14:37 +0200")
and "iso-strict" (e.g. "2019-09-06T03:14:37+02:00").

Steps to reproduce, and actual behavior in bash:

$ LC_ALL=C faketime -f "2019-09-06 03:14:37 02:00" true  # "iso"
[$? = 0]
$ LC_ALL=C faketime -f "2019-09-06T03:14:37+02:00" true  # "iso-strict"
Failed to parse FAKETIME timestamp: Success
[$? = 1]

Expected behavior: Either the second invocation should "just work",
or produce a more meaningful error message.

I prefer the first behavior, and "Success"
sounds like the parsing actually worked, just got handled wrongly,
so maybe this can be done easily?

For my little thing I'll just use git's "iso" shortcut.

Cheers,
Ben Wiederhake

Hi Ben,

thanks for reporting this. Please be advised that a newer release is
available upstream, which however likely is not related to your issue.

With your calls, you should not use the '-f' parameter. Without '-f',
the timestamp is passed on to date/gdate for parsing, which yields the
following for me on Debian Buster x86_64:


./faketime '2019-09-06 03:14:37 02:00' /bin/date
date: invalid date ‘2019-09-06 03:14:37 02:00’
Error: Timestamp to fake not recognized, please re-try with a different
timestamp.

./faketime '2019-09-06T03:14:37+02:00' /bin/date
Fri 06 Sep 2019 03:14:37 AM CEST


So the "iso-strict" variant seems to work out of the box.


When using '-f', the specified string is directly passed on to
libfaketime by the 'faketime' wrapper without parsing (using
date/gdate). In this case, you either have to stick to one of the
formats that libfaketime expects (as documented in the README at
https://github.com/wolfcw/libfaketime), or, which might be more
appropriate for your case, you also have to set the FAKETIME_FMT
environment variable.

I hope that helps a bit.

I also agree that "Success" isn't much of a useful error message here.
In this case, it's created by a call to the standard perror() system
call, which should be considered to be replaced with something more
meaningful. I'll put that on the todo list. :-) However, more useful
error messages are printed by the wrapper when '-f' is not used.


Best regards
Wolfgang


Ben Wiederhake wrote on 08.09.19 20:54:

Hello Wolfgang,

thanks for your quick response!
time passing.
In my case the call goes to a build process which takes several seconds,
and the timestamp that I want to influence is taken at the very end of
it.  So without the '-f', the "fake clock" would show a
non-deterministic, and most likely different, time.  That's exactly the
thing that I want to avoid.

Thanks!  I hoped that it could parse the absolute timestamp anyway, but
4b) is clear enough.  Oh well.

It does indeed, thank you.  Like I already mentioned, in my case git's
`iso` makes faketime happy, and makes me brush up my knowledge on bash.

So in summary:
- The parsing is "as intended".
- git and faketime have different about "strict ISO date formats".
- The bug is actually only the `: Success` part of the output.
Therefore, the bug is only minor.  Also, I have a manual workaround anyway.

Cheers,
Ben Wiederhake

Control: forwarded 939789 https://github.com/wolfcw/libfaketime/pull/368
Control: tags 939789 + patch

I've proposed a patch (attached) for this, and forwarded it upstream, as
this is still an issue on version 0.9.9 and even the upstream git master.

We believe that the bug you reported is fixed in the latest version of
faketime, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 939789@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Daniel Kahn Gillmor <dkg@fifthhorseman.net> (supplier of updated faketime package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Wed, 09 Mar 2022 10:47:30 -0500
Source: faketime
Architecture: source
Version: 0.9.10-1
Distribution: unstable
Urgency: medium
Maintainer: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Changed-By: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Closes: 939789
Changes:
 faketime (0.9.10-1) unstable; urgency=medium
 .
   * new upstream release (no functional changes since previous git snapshot)
     - Closes: #939789
   * move to unstable
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