freebsd-skq/lib/libc/sys/fsync.2
mpp 1d267ab1ce Added a update(4) man page to describe the kernel initiated update
process and changed all of the old references to update(8) to update(4).
1996-02-12 00:45:47 +00:00

104 lines
3.2 KiB
Groff

.\" Copyright (c) 1983, 1993
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.\" @(#)fsync.2 8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.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 IMPLEMENTATION NOTES
.Pp
In the non-threaded library
.Fn fsync
is implemented as the
.Va fsync
syscall.
.Pp
In the threaded library, the
.Va fsync
syscall is assembled to
.Fn _thread_sys_fsync
and
.Fn fsync
is implemented as a function which locks
.Va fd
for read and write, then calls
.Fn _thread_sys_fsync .
Before returning,
.Fn fsync
unlocks
.Va fd .
.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 update 4 ,
.Xr sync 8
.Sh HISTORY
The
.Nm
function call appeared in
.Bx 4.2 .