84d9c625bf
- Fix for possible unset uid/gid in toproto
- Fix for default mtree style
- Update libelf
- Importing libexecinfo
- Resynchronize GCC, mpc, gmp, mpfr
- build.sh: Replace params with show-params.
This has been done as the make target has been renamed in the same
way, while a new target named params has been added. This new
target generates a file containing all the parameters, instead of
printing it on the console.
- Update test48 with new etc/services (Fix by Ben Gras <ben@minix3.org)
get getservbyport() out of the inner loop
Change-Id: Ie6ad5226fa2621ff9f0dee8782ea48f9443d2091
191 lines
5.3 KiB
Groff
191 lines
5.3 KiB
Groff
.\" $NetBSD: fsync.2,v 1.18 2013/09/22 10:02:05 apb Exp $
|
|
.\"
|
|
.\" Copyright (c) 1983, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)fsync.2 8.1 (Berkeley) 6/4/93
|
|
.\"
|
|
.Dd September 22, 2013
|
|
.Dt FSYNC 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm fsync ,
|
|
.Nm fsync_range
|
|
.Nd "synchronize a file's in-core state with that on disk"
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In unistd.h
|
|
.Ft int
|
|
.Fn fsync "int fd"
|
|
.Ft int
|
|
.Fn fsync_range "int fd" "int how" "off_t start" "off_t length"
|
|
.Sh DESCRIPTION
|
|
.Fn fsync
|
|
causes all modified data and attributes of
|
|
.Fa fd
|
|
to be written 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_range
|
|
is similar, but provides control over the region of the file
|
|
to be synchronized, and the method of synchronization.
|
|
.Pp
|
|
These functions should be used by programs that require a file to be
|
|
in a known state, for example, in building a simple transaction
|
|
facility.
|
|
.Pp
|
|
Note that writing the data to a permanent storage device
|
|
does not necessarily write the data to permanent storage media
|
|
within that device;
|
|
for example, after writing data to a disk device, the data might
|
|
reside in a cache within the device, but not yet on
|
|
more permanent storage within the device.
|
|
Neither
|
|
.Fn fsync
|
|
nor the default behavior of
|
|
.Fn fsync_range
|
|
(without the
|
|
.Dv FDISKSYNC
|
|
flag)
|
|
will flush disk caches,
|
|
because they assume that storage devices are able to ensure that
|
|
completed writes are transferred to media some time between the
|
|
write and a power failure or system crash.
|
|
.Pp
|
|
.Fn fsync_range
|
|
causes all modified data starting at
|
|
.Fa start
|
|
for length
|
|
.Fa length
|
|
of
|
|
.Fa fd
|
|
to be written to a permanent storage device.
|
|
If the
|
|
.Fa length
|
|
parameter is zero,
|
|
.Fn fsync_range
|
|
will synchronize all of the file data.
|
|
.Pp
|
|
.Fn fsync_range
|
|
takes a
|
|
.Fa how
|
|
parameter which contains one or more of the following flags:
|
|
.Bl -tag -width FDATASYNC -offset indent
|
|
.It Dv FDATASYNC
|
|
Synchronize the file data and sufficient meta-data to retrieve the
|
|
data for the specified range.
|
|
This is equivalent to
|
|
.Xr fdatasync 2
|
|
on the specified range.
|
|
.It Dv FFILESYNC
|
|
Synchronize all modified file data and meta-data for the specified range.
|
|
This is equivalent to
|
|
.Xr fsync 2
|
|
on the specified range.
|
|
.It Dv FDISKSYNC
|
|
Request the destination device to ensure that the relevant data
|
|
and meta-data is flushed from any cache to permanent storage media.
|
|
In the present implementation, the entire cache on the affected device will
|
|
be flushed, and this may have a significant impact on performance.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Dv FDATASYNC
|
|
and
|
|
.Dv FFILESYNC
|
|
flags are mutually exclusive.
|
|
Either of those flags may be combined with the
|
|
.Dv FDISKSYNC
|
|
flag.
|
|
.Pp
|
|
Note that
|
|
.Fn fsync_range
|
|
requires that the file
|
|
.Fa fd
|
|
must be open for writing, whereas
|
|
.Fn fsync
|
|
does not.
|
|
.Sh RETURN VALUES
|
|
A 0 value is returned on success.
|
|
A \-1 value indicates an error.
|
|
.Sh ERRORS
|
|
.Fn fsync
|
|
or
|
|
.Fn fsync_range
|
|
fail 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
|
|
.Pp
|
|
Additionally,
|
|
.Fn fsync_range
|
|
fails if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
.Fa fd
|
|
is not open for writing.
|
|
.It Bq Er EINVAL
|
|
.Fa start
|
|
+
|
|
.Fa length
|
|
is less than
|
|
.Fa start .
|
|
.El
|
|
.Sh NOTES
|
|
For optimal efficiency, the
|
|
.Fn fsync_range
|
|
call requires that the file system containing the file referenced by
|
|
.Fa fd
|
|
support partial synchronization of file data.
|
|
For file systems which do
|
|
not support partial synchronization, the entire file will be synchronized
|
|
and the call will be the equivalent of calling
|
|
.Fn fsync .
|
|
.Sh SEE ALSO
|
|
.Xr fdatasync 2 ,
|
|
.Xr sync 2 ,
|
|
.Xr sync 8
|
|
.Sh HISTORY
|
|
The
|
|
.Fn fsync
|
|
function call appeared in
|
|
.Bx 4.2 .
|
|
.Pp
|
|
The
|
|
.Fn fsync_range
|
|
function call first appeared in
|
|
.Nx 2.0
|
|
and is modeled after the function available in AIX.
|