msync(3C)                        UNIX System V                        msync(3C)


NAME
      msync - synchronize memory with physical storage

SYNOPSIS
      #include <sys/types.h>
      #include <sys/mman.h>
      int msync(caddrt addr, sizet len, int flags);

DESCRIPTION
      The function msync writes all modified copies of pages over the range
      [addr, addr + len) to their backing storage locations.  msync optionally
      invalidates any copies so that further references to the pages will be
      obtained by the system from their backing storage locations.  The backing
      storage for a modified MAPSHARED mapping is the file the page is mapped
      to; the backing storage for a modified MAPPRIVATE mapping is its swap
      area.

      flags is a bit pattern built from the following values:
                   MSASYNC        perform asynchronous writes
                   MSSYNC         perform synchronous writes
                   MSINVALIDATE   invalidate mappings

      If MSASYNC is set, msync returns immediately once all write operations
      are scheduled; if MSSYNC is set, msync does not return until all write
      operations are completed.

      MSINVALIDATE invalidates all cached copies of data in memory, so that
      further references to the pages will be obtained by the system from their
      backing storage locations.

      The effect of msync(addr, len, flags) is equivalent to:

            memcntl(addr, len, MCSYNC, flags, 0, 0)

SEE ALSO
      memcntl(2), mmap(2), sysconf(3C).

DIAGNOSTICS
      Upon successful completion, the function msync returns 0; otherwise, it
      returns -1 and sets errno to indicate the error.

NOTES
      msync should be used by programs that require a memory object to be in a
      known state, for example, in building transaction facilities.










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