376 lines
12 KiB
Groff
376 lines
12 KiB
Groff
.\" Copyright (c) 1991, 1992, 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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.\" @(#)tty.4 8.3 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd January 11, 2017
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.Dt TTY 4
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.Os
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.Sh NAME
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.Nm tty
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.Nd general terminal interface
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.Sh SYNOPSIS
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.In sys/ioctl.h
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.Sh DESCRIPTION
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This section describes the interface to the terminal drivers
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in the system.
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.Ss Terminal Special Files
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Each hardware terminal port on the system usually has a terminal special device
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file associated with it in the directory ``/dev/'' (for
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example, ``/dev/tty03'').
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When a user logs into
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the system on one of these hardware terminal ports, the system has already
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opened the associated device and prepared the line for normal interactive
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use (see
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.Xr getty 8 . )
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There is also a special case of a terminal file that connects not to
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a hardware terminal port, but to another program on the other side.
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These special terminal devices are called
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.Em ptys
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and provide the mechanism necessary to give users the same interface to the
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system when logging in over a network (using
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.Xr rlogin 1 ,
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or
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.Xr telnet 1
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for example).
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Even in these cases the details of how the terminal
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file was opened and set up is already handled by special software
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in the system.
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Thus, users do not normally need to worry about the details of
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how these lines are opened or used.
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Also, these lines are often used
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for dialing out of a system (through an out-calling modem), but again
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the system provides programs that hide the details of accessing
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these terminal special files (see
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.Xr tip 1 ) .
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.Pp
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When an interactive user logs in, the system prepares the line to
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behave in a certain way (called a
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.Em "line discipline" ) ,
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the particular details of which is described in
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.Xr stty 1
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at the command level, and in
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.Xr termios 4
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at the programming level.
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A user may be concerned with changing
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settings associated with his particular login terminal and should refer
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to the preceding man pages for the common cases.
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The remainder of this man page is concerned
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with describing details of using and controlling terminal devices
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at a low level, such as that possibly required by a program wishing
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to provide features similar to those provided by the system.
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.Ss Terminal File Operations
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All of the following operations are invoked using the
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.Xr ioctl 2
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system call.
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Refer to that man page for a description of the
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.Em request
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and
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.Em argp
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parameters.
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In addition to the ioctl
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.Em requests
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defined here, the specific line discipline
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in effect will define other
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.Em requests
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specific to it (actually
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.Xr termios 4
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defines them as function calls, not ioctl
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.Em requests . )
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The following section lists the available ioctl requests.
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The name of the request, a description of its purpose, and the typed
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.Em argp
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parameter (if any)
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are listed.
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For example, the first entry says
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.Pp
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.D1 Em "TIOCSPGRP int *tpgrp"
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.Pp
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and would be called on the terminal associated with
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file descriptor zero by the following code fragment:
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.Bd -literal
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int pgrp;
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pgrp = getpgrp();
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ioctl(0, TIOCSPGRP, &pgrp);
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.Ed
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.Ss Terminal File Request Descriptions
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.Bl -tag -width TIOCGWINSZ
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.It Dv TIOCSETD Fa int *ldisc
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This call is obsolete but left for compatibility.
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Before
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.Fx 8.0 ,
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it would change to the new line discipline pointed to by
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.Fa ldisc .
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.It Dv TIOCGETD Fa int *ldisc
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Return the current line discipline in the integer pointed to by
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.Fa ldisc .
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.It Dv TIOCSBRK Fa void
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Set the terminal hardware into BREAK condition.
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.It Dv TIOCCBRK Fa void
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Clear the terminal hardware BREAK condition.
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.It Dv TIOCSDTR Fa void
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Assert data terminal ready (DTR).
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.It Dv TIOCCDTR Fa void
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Clear data terminal ready (DTR).
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.It Dv TIOCGPGRP Fa int *tpgrp
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Return the current process group with which the terminal is associated
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in the integer pointed to by
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.Fa tpgrp .
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This is the underlying call that implements the
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.Xr termios 4
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.Fn tcgetattr
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call.
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.It Dv TIOCSPGRP Fa int *tpgrp
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Associate the terminal with the process group (as an integer) pointed to by
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.Fa tpgrp .
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This is the underlying call that implements the
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.Xr termios 4
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.Fn tcsetattr
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call.
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.It Dv TIOCGETA Fa struct termios *term
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Place the current value of the termios state associated with the
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device in the termios structure pointed to by
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.Fa term .
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This is the underlying call that implements the
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.Xr termios 4
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.Fn tcgetattr
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call.
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.It Dv TIOCSETA Fa struct termios *term
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Set the termios state associated with the device immediately.
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This is the underlying call that implements the
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.Xr termios 4
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.Fn tcsetattr
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call with the
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.Dv TCSANOW
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option.
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.It Dv TIOCSETAW Fa struct termios *term
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First wait for any output to complete, then set the termios state
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associated with the device.
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This is the underlying call that implements the
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.Xr termios 4
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.Fn tcsetattr
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call with the
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.Dv TCSADRAIN
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option.
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.It Dv TIOCSETAF Fa struct termios *term
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First wait for any output to complete, clear any pending input,
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then set the termios state associated with the device.
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This is the underlying call that implements the
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.Xr termios 4
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.Fn tcsetattr
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call with the
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.Dv TCSAFLUSH
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option.
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.It Dv TIOCOUTQ Fa int *num
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Place the current number of characters in the output queue in the
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integer pointed to by
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.Fa num .
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.It Dv TIOCSTI Fa char *cp
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Simulate typed input.
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Pretend as if the terminal received the character pointed to by
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.Fa cp .
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.It Dv TIOCNOTTY Fa void
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This call is obsolete but left for compatibility.
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In the past, when a process that did not have a controlling terminal (see
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.Em The Controlling Terminal
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in
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.Xr termios 4 )
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first opened a terminal device, it acquired that terminal as its
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controlling terminal.
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For some programs this was a hazard as they
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did not want a controlling terminal in the first place, and this
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provided a mechanism to disassociate the controlling terminal from
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the calling process.
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It
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.Em must
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be called by opening the file
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.Pa /dev/tty
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and calling
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.Dv TIOCNOTTY
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on that file descriptor.
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.Pp
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The current system does not allocate a controlling terminal to
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a process on an
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.Fn open
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call: there is a specific ioctl called
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.Dv TIOCSCTTY
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to make a terminal the controlling
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terminal.
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In addition, a program can
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.Fn fork
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and call the
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.Fn setsid
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system call which will place the process into its own session - which
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has the effect of disassociating it from the controlling terminal.
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This is the new and preferred method for programs to lose their controlling
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terminal.
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.It Dv TIOCSTOP Fa void
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Stop output on the terminal (like typing ^S at the keyboard).
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.It Dv TIOCSTART Fa void
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Start output on the terminal (like typing ^Q at the keyboard).
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.It Dv TIOCSCTTY Fa void
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Make the terminal the controlling terminal for the process (the process
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must not currently have a controlling terminal).
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.It Dv TIOCDRAIN Fa void
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Wait until all output is drained, or until the drain wait timeout expires.
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.It Dv TIOCGDRAINWAIT Fa int *timeout
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Return the current drain wait timeout in seconds.
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.It Dv TIOCSDRAINWAIT Fa int *timeout
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Set the drain wait timeout in seconds.
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A value of zero disables timeouts.
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The default drain wait timeout is controlled by the tunable
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.Xr sysctl 8
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OID
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.Va kern.tty_drainwait .
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.It Dv TIOCEXCL Fa void
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Set exclusive use on the terminal.
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No further opens are permitted except by root.
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Of course, this means that programs that are run by
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root (or setuid) will not obey the exclusive setting - which limits
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the usefulness of this feature.
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.It Dv TIOCNXCL Fa void
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Clear exclusive use of the terminal.
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Further opens are permitted.
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.It Dv TIOCFLUSH Fa int *what
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If the value of the int pointed to by
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.Fa what
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contains the
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.Dv FREAD
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bit as defined in
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.In sys/file.h ,
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then all characters in the input queue are cleared.
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If it contains the
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.Dv FWRITE
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bit, then all characters in the output queue are cleared.
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If the value of the integer is zero, then it behaves as if both the
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.Dv FREAD
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and
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.Dv FWRITE
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bits were set (i.e., clears both queues).
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.It Dv TIOCGWINSZ Fa struct winsize *ws
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Put the window size information associated with the terminal in the
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.Va winsize
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structure pointed to by
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.Fa ws .
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The window size structure contains the number of rows and columns (and pixels
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if appropriate) of the devices attached to the terminal.
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It is set by user software
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and is the means by which most full\&-screen oriented programs determine the
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screen size.
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The
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.Va winsize
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structure is defined in
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.In sys/ioctl.h .
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.It Dv TIOCSWINSZ Fa struct winsize *ws
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Set the window size associated with the terminal to be the value in
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the
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.Va winsize
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structure pointed to by
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.Fa ws
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(see above).
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.It Dv TIOCCONS Fa int *on
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If
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.Fa on
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points to a non-zero integer, redirect kernel console output (kernel printf's)
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to this terminal.
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If
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.Fa on
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points to a zero integer, redirect kernel console output back to the normal
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console.
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This is usually used on workstations to redirect kernel messages
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to a particular window.
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.It Dv TIOCMSET Fa int *state
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The integer pointed to by
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.Fa state
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contains bits that correspond to modem state.
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Following is a list of defined variables and the modem state they represent:
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.Pp
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.Bl -tag -width TIOCMXCTS -compact
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.It TIOCM_LE
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Line Enable.
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.It TIOCM_DTR
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Data Terminal Ready.
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.It TIOCM_RTS
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Request To Send.
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.It TIOCM_ST
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Secondary Transmit.
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.It TIOCM_SR
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Secondary Receive.
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.It TIOCM_CTS
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Clear To Send.
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.It TIOCM_CAR
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Carrier Detect.
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.It TIOCM_CD
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Carrier Detect (synonym).
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.It TIOCM_RNG
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Ring Indication.
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.It TIOCM_RI
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Ring Indication (synonym).
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.It TIOCM_DSR
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Data Set Ready.
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.El
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.Pp
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This call sets the terminal modem state to that represented by
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.Fa state .
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Not all terminals may support this.
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.It Dv TIOCMGET Fa int *state
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Return the current state of the terminal modem lines as represented
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above in the integer pointed to by
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.Fa state .
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.It Dv TIOCMBIS Fa int *state
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The bits in the integer pointed to by
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.Fa state
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represent modem state as described above, however the state is OR-ed
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in with the current state.
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.It Dv TIOCMBIC Fa int *state
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The bits in the integer pointed to by
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.Fa state
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represent modem state as described above, however each bit which is on
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in
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.Fa state
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is cleared in the terminal.
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.El
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.Sh IMPLEMENTATION NOTES
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The total number of input and output bytes
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through all terminal devices
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are available via the
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.Va kern.tty_nin
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and
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.Va kern.tty_nout
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read-only
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.Xr sysctl 8
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variables.
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.Sh SEE ALSO
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.Xr stty 1 ,
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.Xr ioctl 2 ,
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.Xr ng_tty 4 ,
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.Xr pty 4 ,
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.Xr termios 4 ,
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.Xr getty 8
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