.\" Copyright (c) 1983, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)fsync.2	8.1 (Berkeley) 06/04/93
.\"
.Dd 
.Dt FSYNC 2
.Os BSD 4.2
.Sh NAME
.Nm fsync
.Nd "synchronize a file's in-core state with that on disk"
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fn fsync "int fd"
.Sh DESCRIPTION
.Fn Fsync
causes all modified data and attributes of
.Fa fd
to be moved to a permanent storage device.
This normally results in all in-core modified copies
of buffers for the associated file to be written to a disk.
.Pp
.Fn Fsync
should be used by programs that require a file to be
in a known state, for example, in building a simple transaction
facility.
.Sh RETURN VALUES
A 0 value is returned on success.  A -1 value indicates
an error.
.Sh ERRORS
The
.Fn fsync
fails if:
.Bl -tag -width Er
.It Bq Er EBADF
.Fa Fd
is not a valid descriptor.
.It Bq Er EINVAL
.Fa Fd
refers to a socket, not to a file.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr sync 2 ,
.Xr sync 8 ,
.Xr update 8
.Sh HISTORY
The
.Nm
function call appeared in
.Bx 4.2 .