msync - 同步用的存儲器映射的文件

內容簡介

#include <sys/mman.h>

int msync(void **start*, size_t length**, int** flags**);**

描述

msync () flushes changes made to the in-core copy of a file that was mapped into memory using  mmap (2) back to disk. Without use of this call there is no guarantee that changes are written back before  munmap (2) is called. To be more precise, the part of the file that corresponds to the memory area starting at  start  and having length  length is updated. The  flags  argument may have the bits MS_ASYNC, MS_SYNC and MS_INVALIDATE set, but not both MS_ASYNC and MS_SYNC. MS_ASYNC specifies that an update be scheduled, but the call returns immediately. MS_SYNC asks for an update and waits for it to complete. MS_INVALIDATE asks to invalidate other mappings of the same file (so that they can be updated with the fresh values just written).

返回值

On success, zero is returned. On error, -1 is returned, and  errno  is set appropriately.

錯誤

標籤

描述

EINVAL

start is not a multiple of PAGESIZE; or any bit other than MS_ASYNC | MS_INVALIDATE | MS_SYNC is set in flags; or both MS_SYNC and MS_ASYNC are set in flags.

ENOMEM

The indicated memory (or part of it) was not mapped.

可用性

On POSIX systems on which  msync () is available, both  _POSIX_MAPPED_FILES  and _POSIX_SYNCHRONIZED_IO  are defined in <unistd.h> to a value greater than 0. (See also  sysconf (3).)

遵循於

POSIX.1-2001.

This call was introduced in Linux 1.3.21, and then used EFAULT instead of ENOMEM. In Linux 2.4.19 this was changed to the POSIX value ENOMEM.

另請參閱

• mmap (2)

B.O. Gallmeister, POSIX.4, O’Reilly, pp. 128-129 and 389-391.