156 lines
4.3 KiB
Groff
156 lines
4.3 KiB
Groff
.\" Copyright (c) 1980, 1991, 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.
|
|
.\" 4. 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.
|
|
.\"
|
|
.\" @(#)ioctl.2 8.2 (Berkeley) 12/11/93
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd May 11, 2010
|
|
.Dt IOCTL 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm ioctl
|
|
.Nd control device
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/ioctl.h
|
|
.Ft int
|
|
.Fn ioctl "int d" "unsigned long request" ...
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn ioctl
|
|
system call manipulates the underlying device parameters of special files.
|
|
In particular, many operating
|
|
characteristics of character special files (e.g.\& terminals)
|
|
may be controlled with
|
|
.Fn ioctl
|
|
requests.
|
|
The argument
|
|
.Fa d
|
|
must be an open file descriptor.
|
|
.Pp
|
|
The third argument to
|
|
.Fn ioctl
|
|
is traditionally named
|
|
.Va "char *argp" .
|
|
Most uses of
|
|
.Fn ioctl ,
|
|
however, require the third argument to be a
|
|
.Vt caddr_t
|
|
or an
|
|
.Vt int .
|
|
.Pp
|
|
An
|
|
.Fn ioctl
|
|
.Fa request
|
|
has encoded in it whether the argument is an
|
|
.Dq in
|
|
argument
|
|
or
|
|
.Dq out
|
|
argument, and the size of the argument
|
|
.Fa argp
|
|
in bytes.
|
|
Macros and defines used in specifying an ioctl
|
|
.Fa request
|
|
are located in the file
|
|
.In sys/ioctl.h .
|
|
.Sh GENERIC IOCTLS
|
|
Some generic ioctls are not implemented for all types of file
|
|
descriptors.
|
|
These include:
|
|
.Bl -tag -width "xxxxxx"
|
|
.It Dv FIONREAD int
|
|
Get the number of bytes that are immediately available for reading.
|
|
.It Dv FIONWRITE int
|
|
Get the number of bytes in the descriptor's send queue.
|
|
These bytes are data which has been written to the descriptor but
|
|
which are being held by the kernel for further processing.
|
|
The nature of the required processing depends on the underlying device.
|
|
For TCP sockets, these bytes have not yet been acknowledged by the
|
|
other side of the connection.
|
|
.It Dv FIONSPACE int
|
|
Get the free space in the descriptor's send queue.
|
|
This value is the size of the send queue minus the number of bytes
|
|
being held in the queue.
|
|
Note: while this value represents the number of bytes that may be
|
|
added to the queue, other resource limitations may cause a write
|
|
not larger than the send queue's space to be blocked.
|
|
One such limitation would be a lack of network buffers for a write
|
|
to a network connection.
|
|
.El
|
|
.Sh RETURN VALUES
|
|
If an error has occurred, a value of -1 is returned and
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
The
|
|
.Fn ioctl
|
|
system call
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
The
|
|
.Fa d
|
|
argument
|
|
is not a valid descriptor.
|
|
.It Bq Er ENOTTY
|
|
The
|
|
.Fa d
|
|
argument
|
|
is not associated with a character
|
|
special device.
|
|
.It Bq Er ENOTTY
|
|
The specified request does not apply to the kind
|
|
of object that the descriptor
|
|
.Fa d
|
|
references.
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa request
|
|
or
|
|
.Fa argp
|
|
argument
|
|
is not valid.
|
|
.It Bq Er EFAULT
|
|
The
|
|
.Fa argp
|
|
argument
|
|
points outside the process's allocated address space.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr execve 2 ,
|
|
.Xr fcntl 2 ,
|
|
.Xr intro 4 ,
|
|
.Xr tty 4
|
|
.Sh HISTORY
|
|
The
|
|
.Fn ioctl
|
|
function appeared in
|
|
.At v7 .
|