netbsd man page for msync

MSYNC(2)						      BSD 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 all pages with shared modifications in the specified region of the process's address space back to permanent
     storage, and, if requested, invalidates cached data mapped in the region.	If len is 0, all modified pages within the region containing addr
     will be flushed; if len is non-zero, only modified pages containing addr and len succeeding locations will be flushed.  Any required synchro-
     nization of memory caches will also take place at this time.  Filesystem operations on a file that is mapped for shared modifications are
     unpredictable except after an msync().

     The flags argument is formed by or'ing the following values

	   MS_ASYNC	    Perform asynchronous writes.
	   MS_SYNC	    Perform synchronous writes.
	   MS_INVALIDATE    Invalidate cached data after writing.

RETURN VALUES
     Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS
     The following errors may be reported:

     [EBUSY]		The MS_INVALIDATE flag was specified and a portion of the specified region was locked with mlock(2).

     [EINVAL]		The specified flags argument was invalid.

     [EINVAL]		The addr parameter was not page aligned.

     [EINVAL]		The addr parameter did not specify an address part of a mapped region.

     [EINVAL]		The len parameter was negative.

     [EIO]		An I/O error occurred while writing to the file system.

     [ENOMEM]		Addresses in the specified region are outside the range allowed for the address space of the process, or specify one or
			more pages which are unmapped.

SEE ALSO
     mlock(2), mmap(2), munlock(2)

STANDARDS
     The msync() function conforms to IEEE Std 1003.1b-1993 (``POSIX.1'')

HISTORY
     The msync() function first appeared in 4.4BSD.  It was modified to conform to IEEE Std 1003.1b-1993 (``POSIX.1'') in NetBSD 1.3.

BSD
								 October 17, 2005							       BSD