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RedHat 9 (Linux i386) - man page for msync (redhat section 2)

MSYNC(2)			    Linux Programmer's Manual				 MSYNC(2)

NAME
       msync - synchronize a file with a memory map

SYNOPSIS
       #include <unistd.h>
       #include <sys/mman.h>

       #ifdef _POSIX_MAPPED_FILES
       #ifdef _POSIX_SYNCHRONIZED_IO

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

       #endif
       #endif

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 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_INVALI-
       DATE 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
       EINVAL start is not a multiple of PAGESIZE, or any bit other than MS_ASYNC | MS_INVALIDATE
	      | MS_SYNC is set in flags.

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

CONFORMING TO
       POSIX.1b (formerly POSIX.4)

SEE ALSO
       mmap(2), B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128-129 and 389-391.

Linux 1.3.86				    1996-04-12					 MSYNC(2)


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