[ruby-core:82993] [Ruby trunk Feature#13696] Add exchange and noreplace options to File.rename

Issue #13696 has been updated by shyouhei (Shyouhei Urabe).


I think it's hard to have platform-specific API extensions like this to be in-core.  If atomicity is such an important feature (and I'm sure it is), it's hard to emulate this in pure-userland for people without OS that support it.

This should be implemented as a gem.  That way, gem install can bail out purposefully for unsupported platforms.  That should prevent hidden race condition that you want to avoid.

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Feature #13696: Add exchange and noreplace options to File.rename
https://bugs.ruby-lang.org/issues/13696#change-66901

* Author: Glass_saga (Masaki Matsushita)
* Status: Open
* Priority: Normal
* Assignee: Glass_saga (Masaki Matsushita)
* Target version: 2.5
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renameat2(2) introduced in linux kernel 3.15 takes following flags.

```
RENAME_EXCHANGE: Atomically exchange oldpath and newpath.

RENAME_NOREPLACE: Don't overwrite newpath of the rename. Return an error if newpath already exists.
```

This change makes `File.rename` take these flags as keyword arguments.

Example:

```ruby
File.write("hoge", "hoge")
File.write("fuga", "fuga")
File.rename("hoge", "fuga", exchange: true) # atomically exchanged
File.read("fuga") #=> "hoge"

File.rename("hoge", "fuga", noreplace: true) #=> File exists @ syserr_fail2_in - fuga (Errno::EEXIST)
```

---Files--------------------------------
patch.diff (4.19 KB)
patch.diff (4.84 KB)


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