"synchronize disk block in-core status with that on disk"
#include <unistd.h> voidsync(void);
function forces a write of dirty (modified) buffers
in the block buffer cache out to disk.
The kernel keeps this information in core to reduce
the number of disk I/O transfers required by the system.
As information in the cache is lost after a system crash a
call is issued frequently by the in-kernel process
(about every 30 seconds).
may be used to synchronize individual file descriptor attributes.