msync(3C)

synchronize memory with physical storage

From the original Amiga UNIX 2.1 manual. Some things it mentions may not be in this release.

NAME

msync - synchronize memory with physical storage

SYNOPSIS

#include <sys/types.h>
#include <sys/mman.h>

int msync(caddr_t addr, size_t len, int flags);

DESCRIPTION

The function msync writes all modified copies of pages  over
the  range [addr, addr + len) to their backing storage loca-
tions.  msync optionally  invalidates  any  copies  so  that
further references to the pages will be obtained by the sys-
tem from  their  backing  storage  locations.   The  backing
storage  for  a  modified MAP_SHARED mapping is the file the
page is mapped  to;  the  backing  storage  for  a  modified
MAP_PRIVATE  mapping  is its swap area.  flags is a bit pat-
tern built from the following values:
       MS_ASYNC        perform asynchronous writes
       MS_SYNC         perform synchronous writes
       MS_INVALIDATE   invalidate mappings
If MS_ASYNC is set, msync returns immediately once all write
operations  are scheduled; if MS_SYNC is set, msync does not
return   until   all   write   operations   are   completed.
MS_INVALIDATE  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, MC_SYNC, flags, 0, 0)

DIAGNOSTICS

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

NOTES