sync(2) - NetBSD Manual Pages

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SYNC(2)                   NetBSD Programmer's Manual                   SYNC(2)


NAME

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


LIBRARY

     Standard C Library (libc, -lc)


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

     The function fsync(2) may be used to synchronize individual file descrip-
     tor attributes.


SEE ALSO

     fsync(2), sync(8)


BUGS

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


HISTORY

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

NetBSD 1.5.1                     June 4, 1993                                1