NAME
msync - synchronize a file with a memory map SYNOPSIS
#include
int msync(void *addr, sizet 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 mun‐ map(2) is called. To be more precise, the part of the file that corre‐ sponds to the memory area starting at addr and having length length is updated. The flags argument may have the bits MSASYNC, MSSYNC, and MSINVALI‐ DATE set, but not both MSASYNC and MSSYNC. MSASYNC specifies that an update be scheduled, but the call returns immediately. MSSYNC asks for an update and waits for it to complete. MSINVALIDATE 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 MSINVALIDATE 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 MSASYNC | MSINVALIDATE | MSSYNC is set in flags; or both MSSYNC and MSASYNC 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 POSIXMAPPEDFILES and POSIXSYNCHRONIZEDIO are defined in
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
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Linux 2008-04-22 MSYNC(2)