msync

Flushes dirty pages of a file-backed mapping back to the underlying vnode.

Prototype

int msync(caddr_t addr, size_t len, int flags);

Returns: int

Arguments

Name	Type	Dir
addr	caddr_t	-
len	size_t	-
flags	int	-

Version history

XNU tag	macOS	#
xnu-1456.1.26	macOS 10.6 Snow Leopard	65
xnu-1486.2.11	—	65
xnu-1504.15.3	—	65
xnu-1504.3.12	—	65
xnu-1504.7.4	—	65
xnu-1504.9.17	—	65
xnu-1504.9.26	—	65
xnu-1504.9.37	—	65

Examples

C — synchronous flush

msync(map, len, MS_SYNC);

Notes

msync(2) supports MS_ASYNC (queue the I/O), MS_SYNC (block until completion) and MS_INVALIDATE (drop clean cached pages and force a re-read). For anonymous mappings it is a no-op. macOS routes the write-back through the ubc (unified buffer cache), so the data is visible to subsequent read(2) calls on the same vnode.

Related APIs

mmapmunmapfsyncfdatasyncmadvise