1.\" $OpenBSD: fsync.2,v 1.3 1999/02/27 21:56:16 deraadt 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. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)fsync.2 8.1 (Berkeley) 6/4/93 36.\" 37.Dd June 4, 1993 38.Dt FSYNC 2 39.Os BSD 4.2 40.Sh NAME 41.Nm fsync 42.Nd "synchronize a file's in-core state with that on disk" 43.Sh SYNOPSIS 44.Fd #include <unistd.h> 45.Ft int 46.Fn fsync "int fd" 47.Sh DESCRIPTION 48.Fn fsync 49causes all modified data and attributes of 50.Fa fd 51to be moved to a permanent storage device. 52This normally results in all in-core modified copies 53of buffers for the associated file to be written to a disk. 54.Pp 55.Fn fsync 56should be used by programs that require a file to be 57in a known state, for example, in building a simple transaction 58facility. 59.Sh RETURN VALUES 60A 0 value is returned on success. A -1 value indicates 61an error. 62.Sh ERRORS 63The 64.Fn fsync 65fails if: 66.Bl -tag -width Er 67.It Bq Er EBADF 68.Fa fd 69is not a valid descriptor. 70.It Bq Er EINVAL 71.Fa fd 72refers to a socket, not to a file. 73.It Bq Er EIO 74An I/O error occurred while reading from or writing to the file system. 75.El 76.Sh SEE ALSO 77.Xr sync 2 , 78.Xr sync 8 , 79.Xr update 8 80.Sh HISTORY 81The 82.Fn fsync 83function call appeared in 84.Bx 4.2 . 85