MSYNC(2) |
Linux Programmer's Manual |
MSYNC(2) |
NAME
msync - synchronize a file with a memory map
SYNOPSIS
#include <sys/mman.h>
int msync(void *
addr
, size_t
length
, int
flags
);
DESCRIPTION
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
addr 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).
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and
errno is set appropriately.
ERRORS
-
EBUSY
-
MS_INVALIDATE was specified in
flags, and a memory lock exists for the specified address range.
-
EINVAL
-
addr 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.
CONFORMING TO
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.
AVAILABILITY
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).)
SEE ALSO
mmap(2)
B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128-129 and 389-391.
COLOPHON
This page is part of release 3.53 of the Linux
man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.