|
|
msync — synchronize a file with a memory map
#include <sys/mman.h>
int
msync( |
void *addr, |
| size_t length, | |
int flags); |
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).
On success, zero is returned. On error, −1 is
returned, and errno is set
appropriately.
MS_INVALIDATE was
specified in flags, and a memory lock
exists for the specified address range.
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.
The indicated memory (or part of it) was not mapped.
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.
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).)