NAME    [Toc]    [Back]

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

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

     #include <unistd.h>

     void
     sync(void);

DESCRIPTION    [Toc]    [Back]

     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, kernel thread
     ioflush ensures that dirty buffers are synced to disk eventually. By
     default, a dirty buffer is synced after 30 seconds, but some filesystems
     exploit ioflush features to sync directory data and metadata faster
     (after 15 and 10 seconds, respectively).

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

SEE ALSO    [Toc]    [Back]

     fsync(2), sync(8)

HISTORY    [Toc]    [Back]

     A sync() function call appeared in Version 6 AT&T UNIX.

BUGS    [Toc]    [Back]

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

BSD                              June 4, 1993                              BSD