Atomic file swapping

Sadly, no, this is not a nuclear-powered utility to swap files. atomicswap is a Python module that implements the swapping of two files on a filesystem in a single operation that can't be broken up; either the entire operation completes correctly or none of it completes. This prevents the filesystem from being left in an inconsistent state and avoids certain race conditions.

The API is very simple; only a single swap() function is provided. The function takes two file paths for the two files to be swapped. In the event that either path is a relative path, you may also provide file descriptors for directories that the relative paths should start from; if either is missing then the path is relative to the current working directory. Paths can be provided either as Python strings or pathlib paths.

Example

Swapping the files /etc/something/active and /etc/something/standby in a single operation can be performed as follows:

from atomicswap import swap
...
swap("/etc/something/active", "/etc/something/standby")

Alternatively, if using Path objects, this could be implemented as:

from pathlib import Path
from atomicswap import swap
...
base_dir = Path("/etc/something")
swap(base_dir / "active", base_dir / "standby")

Platform support

Currently atomicswap supports Linux and macOS. A Windows version is a possibility in the future.

License

atomicswap is released under the MIT license. See LICENSE.md for details.