Function atomic_cp 

pub fn atomic_cp(from: &Path, to: &Path) -> Result<()>

Atomically copies a file from from to to.

The content is first written to a uniquely named temporary sibling (with PID and timestamp) and then moved into place with std::fs::rename. This minimizes the window where readers could observe a partially written file.

Errors

• A filesystem operation (open/read/write/remove) fails.
• from Does not exist.
• The atomic rename fails.
• The destination’s parent directory or file name cannot be resolved.
• The temporary copy fails.