SYNOPSISIn sys/mman.h Ft int Fn msync void *addr size_t len int flags
DESCRIPTIONThe Fn msync system call writes any modified pages back to the file system and updates the file modification time. If Fa len is 0, all modified pages within the region containing Fa addr will be flushed; if Fa len is non-zero, only those pages containing Fa addr and Fa len-1 succeeding locations will be examined. The Fa flags argument may be specified as follows:
- Return immediately
- Perform synchronous writes
- Invalidate all cached data
RETURN VALUESRv -std msync
ERRORSThe Fn msync system call will fail if:
- Bq Er EBUSY
- Some or all of the pages in the specified region are locked and MS_INVALIDATE is specified.
- Bq Er EINVAL
- The Fa addr argument is not a multiple of the hardware page size.
- Bq Er ENOMEM
- The addresses in the range starting at Fa addr and continuing for Fa len bytes are outside the range allowed for the address space of a process or specify one or more pages that are not mapped.
- Bq Er EINVAL
- The Fa flags argument was both MS_ASYNC and MS_INVALIDATE. Only one of these flags is allowed.
- Bq Er EIO
- An error occurred while writing at least one of the pages in the specified region.
HISTORYThe Fn msync system call first appeared in BSD 4.4
BUGSThe Fn msync system call is usually not needed since BSD implements a coherent file system buffer cache. However, it may be used to associate dirty VM pages with file system buffers and thus cause them to be flushed to physical media sooner rather than later.