1.\" Copyright (c) 1983, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)fsync.2 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd June 4, 1993 36.Dt FSYNC 2 37.Os 38.Sh NAME 39.Nm fsync 40.Nd "synchronise changes to a file" 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In unistd.h 45.Ft int 46.Fn fsync "int fd" 47.Sh DESCRIPTION 48The 49.Fn fsync 50system call 51causes all modified data and attributes of 52.Fa fd 53to be moved to a permanent storage device. 54This normally results in all in-core modified copies 55of buffers for the associated file to be written to a disk. 56.Pp 57The 58.Fn fsync 59system call 60should be used by programs that require a file to be 61in a known state, for example, in building a simple transaction 62facility. 63.Sh RETURN VALUES 64.Rv -std fsync 65.Sh ERRORS 66The 67.Fn fsync 68fails if: 69.Bl -tag -width Er 70.It Bq Er EBADF 71The 72.Fa fd 73argument 74is not a valid descriptor. 75.It Bq Er EINVAL 76The 77.Fa fd 78argument 79refers to a socket, not to a file. 80.It Bq Er EIO 81An I/O error occurred while reading from or writing to the file system. 82.El 83.Sh SEE ALSO 84.Xr sync 2 , 85.Xr syncer 4 , 86.Xr sync 8 87.Sh HISTORY 88The 89.Fn fsync 90system call appeared in 91.Bx 4.2 . 92