fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
156 lines
4.3 KiB
Groff
156 lines
4.3 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)ioctl.2 8.2 (Berkeley) 12/11/93
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 11, 2013
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.Dt IOCTL 2
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.Os
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.Sh NAME
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.Nm ioctl
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.Nd control device
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/ioctl.h
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.Ft int
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.Fn ioctl "int fd" "unsigned long request" ...
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.Sh DESCRIPTION
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The
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.Fn ioctl
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system call manipulates the underlying device parameters of special files.
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In particular, many operating
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characteristics of character special files (e.g.\& terminals)
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may be controlled with
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.Fn ioctl
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requests.
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The argument
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.Fa fd
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must be an open file descriptor.
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.Pp
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The third argument to
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.Fn ioctl
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is traditionally named
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.Va "char *argp" .
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Most uses of
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.Fn ioctl ,
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however, require the third argument to be a
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.Vt caddr_t
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or an
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.Vt int .
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.Pp
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An
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.Fn ioctl
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.Fa request
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has encoded in it whether the argument is an
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.Dq in
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argument
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or
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.Dq out
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argument, and the size of the argument
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.Fa argp
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in bytes.
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Macros and defines used in specifying an ioctl
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.Fa request
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are located in the file
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.In sys/ioctl.h .
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.Sh GENERIC IOCTLS
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Some generic ioctls are not implemented for all types of file
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descriptors.
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These include:
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.Bl -tag -width "xxxxxx"
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.It Dv FIONREAD int
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Get the number of bytes that are immediately available for reading.
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.It Dv FIONWRITE int
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Get the number of bytes in the descriptor's send queue.
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These bytes are data which has been written to the descriptor but
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which are being held by the kernel for further processing.
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The nature of the required processing depends on the underlying device.
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For TCP sockets, these bytes have not yet been acknowledged by the
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other side of the connection.
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.It Dv FIONSPACE int
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Get the free space in the descriptor's send queue.
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This value is the size of the send queue minus the number of bytes
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being held in the queue.
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Note: while this value represents the number of bytes that may be
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added to the queue, other resource limitations may cause a write
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not larger than the send queue's space to be blocked.
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One such limitation would be a lack of network buffers for a write
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to a network connection.
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.El
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.Sh RETURN VALUES
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If an error has occurred, a value of -1 is returned and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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The
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.Fn ioctl
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system call
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa fd
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argument
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is not a valid descriptor.
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.It Bq Er ENOTTY
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The
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.Fa fd
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argument
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is not associated with a character
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special device.
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.It Bq Er ENOTTY
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The specified request does not apply to the kind
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of object that the descriptor
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.Fa fd
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references.
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.It Bq Er EINVAL
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The
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.Fa request
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or
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.Fa argp
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argument
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is not valid.
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.It Bq Er EFAULT
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The
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.Fa argp
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argument
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points outside the process's allocated address space.
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.El
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.Sh SEE ALSO
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.Xr execve 2 ,
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.Xr fcntl 2 ,
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.Xr intro 4 ,
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.Xr tty 4
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.Sh HISTORY
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The
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.Fn ioctl
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function appeared in
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.At v7 .
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