sync(2) - NetBSD Manual Pages

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SYNC(2)                   NetBSD System Calls 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
     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 descrip-
     tor attributes.


SEE ALSO

     fsync(2), sync(8)


HISTORY

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


BUGS

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

NetBSD 4.0                       June 4, 1993                       NetBSD 4.0