sync(2) — SYSTEM CALLS
NAME
sync − update super block
SYNOPSIS
#include <unistd.h>
void sync(void);
DESCRIPTION
sync causes all information in memory that should be on disk to be written out. This includes modified super blocks, modified i-nodes, and delayed block I/O.
It should be used by programs that examine a file system, such as fsck(1M), df(1M), and so on. It is mandatory before a re-boot.
The writing, although scheduled, is not necessarily completed before sync returns. The fsync system call completes the writing before it returns.