Function write_atomic 

pub fn write_atomic(path: &Path, contents: impl AsRef<[u8]>) -> Result<()>

Atomically replace path with contents.

Examples

The destination either holds the old bytes or the new ones. A reader racing the write never sees a prefix of the new contents, which is the whole reason this is not fs::write.

let dir = std::env::temp_dir().join("choir-fs-doctest-write-atomic");
fs::create_dir_all(&dir)?;
let path = dir.join("policy");

choir_fs::atomic_file::write_atomic(&path, "first\n")?;
assert_eq!(fs::read_to_string(&path)?, "first\n");

// Replacing is one rename, not a truncate-then-write.
choir_fs::atomic_file::write_atomic(&path, "second\n")?;
assert_eq!(fs::read_to_string(&path)?, "second\n");

// Nothing is left behind in the directory the temp file was written to.
let strays: Vec<_> = fs::read_dir(&dir)?
    .filter_map(Result::ok)
    .filter(|e| e.file_name() != "policy")
    .collect();
assert!(strays.is_empty(), "temp file survived the rename");

Errors

Any io::Error from creating, writing, syncing or renaming the replacement file, and InvalidInput when path has no parent directory to write the replacement into.