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 .Fo sync
  46 .Fa void
  47 .Fc
  48 .Sh DESCRIPTION
  49 The
  50 .Fn sync
  51 function forces a write of dirty (modified) buffers
  52 in the block buffer cache out
  53 to disk. The kernel keeps this information in core to reduce
  54 the number of disk I/O transfers required by the system.
  55 As information in the cache is lost after a system crash a
  56 .Fn sync
  57 call is issued
  58 frequently
  59 by the user process
  60 .Xr update 8
  61 (about every 30 seconds).
  62 .Pp
  63 The function
  64 .Xr fsync 2
  65 may be used to synchronize individual file descriptor
  66 attributes.
  67 .Sh SEE ALSO
  68 .Xr fsync 2 ,
  69 .Xr sync 8 ,
  70 .Xr update 8
  71 .Sh BUGS
  72 .Fn Sync
  73 may return before the buffers are completely flushed.
  74 .Sh HISTORY
  75 A
  76 .Fn sync
  77 function call appeared in
  78 .At v6 .