1.\" $NetBSD: ioctl.2,v 1.18 2004/05/13 10:20:58 wiz Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)ioctl.2 8.2 (Berkeley) 12/11/93 31.\" 32.Dd August 11, 2002 33.Dt IOCTL 2 34.Os 35.Sh NAME 36.Nm ioctl 37.Nd control device 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/ioctl.h 42.Ft int 43.Fn ioctl "int d" "unsigned long request" "void *argp" 44.Sh DESCRIPTION 45The 46.Fn ioctl 47function manipulates the underlying device parameters of special files. 48In particular, many operating 49characteristics of character special files (e.g. terminals) 50may be controlled with 51.Fn ioctl 52requests. 53The argument 54.Fa d 55must be an open file descriptor. 56.Pp 57An ioctl 58.Fa request 59has encoded in it whether the argument is an 60.Dq in 61parameter 62or 63.Dq out 64parameter, and the size of the argument 65.Fa argp 66in bytes. 67Macros and defines used in specifying an ioctl 68.Fa request 69are located in the file 70.Ao Pa sys/ioctl.h Ac . 71.Sh GENERIC IOCTLS 72Some ioctls are applicable to any file descriptor. 73These include: 74.Bl -tag -width "xxxxxx" 75.It Dv FIOCLEX 76Set close-on-exec flag. 77The file will be closed when 78.Xr exec 3 79is invoked. 80.It Dv FIONCLEX 81Clear close-on-exec flag. 82The file will remain open across 83.Xr exec 3 . 84.El 85.Pp 86Some generic ioctls are not implemented for all types of file 87descriptors. 88These include: 89.Bl -tag -width "xxxxxx" 90.It Dv FIONREAD "int" 91Get the number of bytes that are immediately available for reading. 92.It Dv FIONBIO "int" 93Set non-blocking I/O mode if the argument is non-zero. 94In non-blocking mode, 95.Xr read 2 96or 97.Xr write 2 98calls return \-1 and set 99.Va errno 100to 101.Er EAGAIN 102immediately when no data is available. 103.It Dv FIOASYNC "int" 104Set asynchronous I/O mode if the argument is non-zero. 105In asynchronous mode, the process or process group specified by 106.Dv FIOSETOWN 107will start receiving 108.Dv SIGIO 109signals when data is available. 110The 111.Dv SIGIO 112signal will be delivered when data is available on the file 113descriptor. 114.It Dv FIOSETOWN, FIOGETOWN "int" 115Set/get the process or the process group (if negative) that should receive 116.Dv SIGIO 117signals when data is available. 118.El 119.Sh RETURN VALUES 120If an error has occurred, a value of \-1 is returned and 121.Va errno 122is set to indicate the error. 123.Sh ERRORS 124.Fn ioctl 125will fail if: 126.Bl -tag -width Er 127.It Bq Er EBADF 128.Fa d 129is not a valid descriptor. 130.It Bq Er ENOTTY 131.Fa d 132is not associated with a character 133special device. 134.It Bq Er ENOTTY 135The specified request does not apply to the kind 136of object that the descriptor 137.Fa d 138references. 139.It Bq Er EINVAL 140.Fa request 141or 142.Fa argp 143is not valid. 144.It Bq Er EFAULT 145.Fa argp 146points outside the process's allocated address space. 147.El 148.Sh SEE ALSO 149.Xr mt 1 , 150.Xr execve 2 , 151.Xr fcntl 2 , 152.Xr intro 4 , 153.Xr tty 4 154.Sh HISTORY 155An 156.Fn ioctl 157function call appeared in 158.At v7 . 159