1.\" $NetBSD: fdatasync.2,v 1.11 2002/10/02 10:36:44 wiz Exp $ 2.\" 3.\" Copyright (c) 1998 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Klaus Klein. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 29.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.Dd May 30, 1998 38.Dt FDATASYNC 2 39.Os 40.Sh NAME 41.Nm fdatasync 42.Nd synchronize the data of a file 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.Fd #include \*[Lt]unistd.h\*[Gt] 47.Ft int 48.Fn fdatasync "int fd" 49.Sh DESCRIPTION 50The 51.Fn fdatasync 52function forces all modified data associated with the file descriptor 53.Fa fd 54to be flushed to stable storage. 55.Pp 56The functionality is as described for 57.Xr fsync 2 , 58with the exception that file status information need not be synchronized, 59which may result in a performance gain, compared to 60.Xr fsync 2 . 61This behaviour is commonly known as 62.Bf -symbolic 63synchronized I/O data integrity completion. 64.Ef 65.Sh RETURN VALUES 66A value of 0 is returned on success. 67Otherwise, a value -1 is returned and 68.Va errno 69is set to indicate the error. 70.Sh ERRORS 71The 72.Fn fdatasync 73function will fail if: 74.Bl -tag -width Er 75.It Bq Er EBADF 76The 77.Fa fd 78argument is not a valid file descriptor. 79.It Bq Er EINVAL 80This implementation does not support synchronized I/O for this file. 81.It Bq Er ENOSYS 82The 83.Fn fdatasync 84function is not supported by this implementation. 85.El 86.Pp 87In the event that any of the I/O operations to be performed fail, 88.Fn fdatasync 89returns the error conditions defined for 90.Xr read 2 91and 92.Xr write 2 , 93and outstanding I/O operations are not guaranteed to have been completed. 94.Sh SEE ALSO 95.Xr fsync 2 , 96.Xr open 2 , 97.Xr read 2 , 98.Xr write 2 99.Sh STANDARDS 100The 101.Fn fdatasync 102function conforms to 103.St -p1003.1b-93 . 104