What does double tilde mean in RPM requirements?

Ask Fedora
1

I’ve noticed that RPM packages sometimes have requirements where version numbers are suffixed with double tildes. For example python3-django-5.1.7-2.fc42 has this requirement (among others):
(python3.13dist(asgiref) < 4~~ with python3.13dist(asgiref) >= 3.8.1)
I fail to google up the meaning of 4~~ rather than a plain 4. Does anyone here know?

2

I think it is meant to be a rough ASCII approximation to the math relation ≈ (almost equal to).

3

Thank you! That sounds plausible, but what would that actually mean? What versions of python3.13dist(asgiref) does python3-django allow, and what versions doesn’t it allow? It needs to be at least 3.8.1 obviously, but what exactly is the upper limit?

4

FWIW, here is what I could find.

Excerpted from fedoraproject.org – wiki – non-numeric versions:

Non-Numeric Versions

There are three cases in which non-numeric versions occur in the Version field:

Pre-release packages
Post-release packages
Snapshot packages

Pre-Release Packages

Non-numeric versioned “pre-release” packages can be problematic so they must be treated with care. These are cases where the upstream “pre-release” version has letters rather than simple numbers in their version. Often they have tags like alpha, beta, rc, or letters like a and b denoting that it is a version before the “final” number. We need to follow a special scheme to ensure proper ordering in the Version field.

Version Tag for Pre-Release Packages: %{X}~%{alphatag}

Where %{X} is the software version that the pre-release will become, and %{alphatag} is the string indicating the pre-release state. In this case, the tilde ‘~’ is used as not only a separator, but also an indicator for RPM to consider it lower than a package that just has %{X} in the Version field.

I also see a commit where a ~ was changed to ~~ for “dev” packages (“pre” packages continue to use the ~ separator):

        if self.pre:
            rpm_suffix = '~{}'.format(''.join(str(x) for x in self.pre))
        elif self.dev:
-           rpm_suffix = '~{}'.format(''.join(str(x) for x in self.dev))
+           rpm_suffix = '~~{}'.format(''.join(str(x) for x in self.dev))
        elif self.post:
            rpm_suffix = '^post{}'.format(self.post[1])
        else:

Edit: That documentation I found was a draft. Here is the current/official documentation: Versioning Guidelines :: Fedora Docs

1 Like
5

Thanks again! I think I understand now.

I was aware of using ~ as a separator to mark prerelease versions as earlier than the final release. But I had always thought of it as a thing splitting a full release number in a left and right side. The commit you found made me realise a tilde simply means a version before whatever is to the left, even if that part itself contains a tilde. Some experiments with rpmdev-vercmp seems to confirm that. Add to that the fact that a version that is a prefix of another version is considered less, the “empty” prerelease before the second tilde in my 4~~ example becomes less than any actual prerelese. And the empty field after the second tilde becomes less than any version with an empty prerelease but a non-empty dev part in the terms of the Python script.

So < 4~~ is used to say "before major version 4 or any prerelese, development, or other preliminary variant of version 4”. An actual version 3 in other words.

In retrospect it almost looks obvious, but I didn’t realize it.

It would break if anyone would make an “pre-dev” version numbered 4~~~. But let’s hope that doesn’t happen. :slight_smile:

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