Module sys/file

Async and sync file operations.

Provides low-level file I/O wrappers around the C runtime externs.

Async operations return IoFuture which resolves to:

• Positive value: success (fd for open, bytes for read/write, 0 for others)
• Negative value: -errno on failure

Stability

unstable — a raw wrapper over the C file calls whose async results are a bare i32 that is a value on success and -errno on failure, which a caller converts with IoError.from_result. std/fs is the typed face (File, read_to_string, write, the Reader/Writer impls) and is what should be imported.

It freezes, if ever, as an implementation detail of std/fs. The one thing worth knowing before then is that the *u8 + length parameter shape here is the same one std/io's traits carry, for the same reason — Yo has no slice type — so if a slice type arrives, both layers change together.