MSYNC(2) Linux Programmer's Manual MSYNC(2)
NAME
msync - synchronize a file(1,n) with a memory map
SYNOPSIS
#include <sys/mman.h>
int msync(void *start, size_t length, int flags);
DESCRIPTION
msync flushes changes made to the in-core copy of a file(1,n) 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 mun-
map(2) is called. To be more precise, the part of the file(1,n) that corre-
sponds 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(7,n,1 builtins), but not both MS_ASYNC and MS_SYNC. MS_ASYNC speci-
fies that an update(7,n) be scheduled, but the call returns immediately.
MS_SYNC asks for an update(7,n) and waits for it to complete. MS_INVALIDATE
asks to invalidate other mappings of the same file(1,n) (so that they can be
updated with the fresh values just written).
RETURN VALUE
On success, zero is returned. On error(8,n), -1 is returned, and errno is
set(7,n,1 builtins) appropriately.
ERRORS
EINVAL start is not a multiple of PAGESIZE, or any bit other than
MS_ASYNC | MS_INVALIDATE | MS_SYNC is set(7,n,1 builtins) in(1,8) flags.
ENOMEM The indicated memory (or part of it) was not mapped.
AVAILABILITY
On POSIX systems on which msync is available, both _POSIX_MAPPED_FILES
and _POSIX_SYNCHRONIZED_IO are defined in(1,8) <unistd.h> to a value greater
than 0. (See also sysconf(3).)
CONFORMING TO
POSIX.1b (formerly POSIX.4)
This call was introduced in(1,8) Linux 1.3.21, and then used EFAULT instead
of ENOMEM. In Linux 2.4.19 this was changed to the POSIX value ENOMEM.
SEE ALSO
mmap(2)
B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128-129 and 389-391.
Linux 2.4 2003-08-21 MSYNC(2)