Function write_atomic 

pub fn write_atomic(
    path: impl AsRef<Path>,
    write: impl FnOnce(&mut dyn Write) -> Result<()>,
) -> Result<()>

Write path atomically: stream through write into a temp file in the same directory, then persist it over path in a single rename. A failed or interrupted write leaves path untouched, so a concurrent reader never observes a half-written file. Delegates the platform-specific atomic replace to tempfile, which handles the Unix and Windows differences.

The temp file is a sibling of path so the rename stays within one filesystem (a metadata move, not a copy). path must have a parent or be relative to the current directory.