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MSYNC(2)		  FreeBSD System Calls Manual		      MSYNC(2)

NAME
     msync -- synchronize a mapped region

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <sys/mman.h>

     int
     msync(void	*addr, size_t len, int flags);

DESCRIPTION
     The msync() system	call writes any	modified pages back to the file	system
     and updates the file modification time.  If len is	0, all modified	pages
     within the	region containing addr will be flushed;	if len is non-zero,
     only those	pages containing addr and len-1	succeeding locations will be
     examined.	The flags argument may be specified as follows:

     MS_ASYNC	    Return immediately
     MS_SYNC	    Perform synchronous	writes
     MS_INVALIDATE  Invalidate all cached data

RETURN VALUES
     The msync() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     The msync() system	call will fail if:

     [EBUSY]		Some or	all of the pages in the	specified region are
			locked and MS_INVALIDATE is specified.

     [EINVAL]		The addr argument is not a multiple of the hardware
			page size.

     [ENOMEM]		The addresses in the range starting at addr and	con-
			tinuing	for len	bytes are outside the range allowed
			for the	address	space of a process or specify one or
			more pages that	are not	mapped.

     [EINVAL]		The flags argument was both MS_ASYNC and MS_INVALI-
			DATE.  Only one	of these flags is allowed.

     [EIO]		An error occurred while	writing	at least one of	the
			pages in the specified region.

SEE ALSO
     madvise(2), mincore(2), mlock(2), mprotect(2), munmap(2)

HISTORY
     The msync() system	call first appeared in 4.4BSD.

BUGS
     The msync() system	call is	usually	not needed since BSD implements	a
     coherent file system buffer cache.	 However, it may be used to associate
     dirty VM pages with file system buffers and thus cause them to be flushed
     to	physical media sooner rather than later.

FreeBSD	9.3			March 18, 2012			   FreeBSD 9.3

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | BUGS

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