1.\" Copyright (c) 1983, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.man% 5.\" 6.\" @(#)fsync.2 8.1 (Berkeley) 06/04/93 7.\" 8.Dd 9.Dt FSYNC 2 10.Os BSD 4.2 11.Sh NAME 12.Nm fsync 13.Nd "synchronize a file's in-core state with that on disk" 14.Sh SYNOPSIS 15.Fd #include <unistd.h> 16.Ft int 17.Fn fsync "int fd" 18.Sh DESCRIPTION 19.Fn Fsync 20causes all modified data and attributes of 21.Fa fd 22to be moved to a permanent storage device. 23This normally results in all in-core modified copies 24of buffers for the associated file to be written to a disk. 25.Pp 26.Fn Fsync 27should be used by programs that require a file to be 28in a known state, for example, in building a simple transaction 29facility. 30.Sh RETURN VALUES 31A 0 value is returned on success. A -1 value indicates 32an error. 33.Sh ERRORS 34The 35.Fn fsync 36fails if: 37.Bl -tag -width Er 38.It Bq Er EBADF 39.Fa Fd 40is not a valid descriptor. 41.It Bq Er EINVAL 42.Fa Fd 43refers to a socket, not to a file. 44.It Bq Er EIO 45An I/O error occurred while reading from or writing to the file system. 46.El 47.Sh SEE ALSO 48.Xr sync 2 , 49.Xr sync 8 , 50.Xr update 8 51.Sh HISTORY 52The 53.Nm 54function call appeared in 55.Bx 4.2 . 56