NAME

sync — synchronize disk block in-core status with that on disk

SYNOPSIS

#include <unistd.h>

void
sync(void);

DESCRIPTION

The sync() 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 sync() call is issued frequently by the in-kernel process update (about every 30 seconds).

The function fsync(2) may be used to synchronize individual file descriptor attributes.

SEE ALSO

fsync(2), sync(8)

STANDARDS

The sync() function conforms to IEEE Std 1003.1-2008 (“POSIX.1”).

HISTORY

A sync() function appeared in Version 2 AT&T UNIX.

BUGS

sync() may return before the buffers are completely flushed.