bsd/man/man2/sync.2

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  34 .\"     @(#)sync.2      8.1 (Berkeley) 6/4/93
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  36 .Dd June 4, 1993
  37 .Dt SYNC 2
  38 .Os BSD 4
  39 .Sh NAME
  40 .Nm sync
  41 .Nd "synchronize disk block in-core status with that on disk"
  42 .Sh SYNOPSIS
  43 .Fd #include <unistd.h>
  44 .Ft void
  45 .Fn sync void
  46 .Sh DESCRIPTION
  47 The
  48 .Fn sync
  49 function forces a write of dirty (modified) buffers
  50 in the block buffer cache out
  51 to disk. The kernel keeps this information in core to reduce
  52 the number of disk I/O transfers required by the system.
  53 As information in the cache is lost after a system crash a
  54 .Fn sync
  55 call is issued
  56 frequently
  57 by the user process
  58 .Xr update 8
  59 (about every 30 seconds).
  60 .Pp
  61 The function
  62 .Xr fsync 2
  63 may be used to synchronize individual file descriptor
  64 attributes.
  65 .Sh SEE ALSO
  66 .Xr fsync 2 ,
  67 .Xr sync 8 ,
  68 .Xr update 8
  69 .Sh BUGS
  70 .Fn Sync
  71 may return before the buffers are completely flushed.
  72 .Sh HISTORY
  73 A
  74 .Fn sync
  75 function call appeared in
  76 .At v6 .