1.\" $OpenBSD: fsync.2,v 1.8 2007/05/31 19:19:32 jmc Exp $ 2.\" $NetBSD: fsync.2,v 1.4 1995/02/27 12:32:38 cgd Exp $ 3.\" 4.\" Copyright (c) 1983, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)fsync.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd $Mdocdate: May 31 2007 $ 34.Dt FSYNC 2 35.Os 36.Sh NAME 37.Nm fsync 38.Nd "synchronize a file's in-core state with that on disk" 39.Sh SYNOPSIS 40.Fd #include <unistd.h> 41.Ft int 42.Fn fsync "int fd" 43.Sh DESCRIPTION 44.Fn fsync 45causes all modified data and attributes of 46.Fa fd 47to be moved to a permanent storage device. 48This normally results in all in-core modified copies 49of buffers for the associated file to be written to a disk. 50.Pp 51.Fn fsync 52should be used by programs that require a file to be in a known state, 53for example, in building a simple transaction facility. 54.Sh RETURN VALUES 55A 0 value is returned on success. 56A \-1 value indicates an error. 57.Sh ERRORS 58The 59.Fn fsync 60fails if: 61.Bl -tag -width Er 62.It Bq Er EBADF 63.Fa fd 64is not a valid descriptor. 65.It Bq Er EINVAL 66.Fa fd 67refers to a socket, not to a file. 68.It Bq Er EIO 69An I/O error occurred while reading from or writing to the file system. 70.El 71.Sh SEE ALSO 72.Xr sync 2 , 73.Xr sync 8 , 74.Xr update 8 75.Sh HISTORY 76The 77.Fn fsync 78function call appeared in 79.Bx 4.2 . 80