Provided by: freebsd-manpages_7.0-2_all bug

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.

     [EINVAL]           The len argument is too large or negative.

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

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     The msync() system call is obsolete since BSD implements a coherent file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.