freebsd-dev/share/man/man4/pts.4

.\" Copyright (c) 1983, 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.
.\" 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.
.\"
.\"     @(#)pty.4	8.2 (Berkeley) 11/30/93
.\" $FreeBSD$
.\"
.Dd August 20, 2008
.Dt PTS 4
.Os
.Sh NAME
.Nm pts
.Nd pseudo-terminal driver
.Sh DESCRIPTION
The
.Nm
driver provides support for a device-pair termed a
.Em pseudo-terminal .
A pseudo-terminal is a pair of character devices, a
.Em master
device and a
.Em slave
device.
The slave device provides to a process an interface identical
to that described in
.Xr tty 4 .
However, whereas all other devices which provide the
interface described in
.Xr tty 4
have a hardware device of some sort behind them, the slave
device has, instead, another process manipulating
it through the master half of the pseudo-terminal.
That is, anything written on the master device is
given to the slave device as input and anything written
on the slave device is presented as input on the master
device.
.Pp
The following
.Xr ioctl 2
calls apply only to pseudo-terminals:
.Bl -tag -width TIOCPTMASTER
.It Dv TIOCPKT
Enable/disable
.Em packet
mode.
Packet mode is enabled by specifying (by reference)
a nonzero parameter and disabled by specifying (by reference)
a zero parameter.
When applied to the master side of a pseudo-terminal, each subsequent
.Xr read 2
from the terminal will return data written on the slave part of
the pseudo-terminal preceded by a zero byte (symbolically
defined as
.Dv TIOCPKT_DATA ) ,
or a single byte reflecting control
status information.
In the latter case, the byte is an inclusive-or
of zero or more of the bits:
.Bl -tag -width TIOCPKT_FLUSHWRITE
.It Dv TIOCPKT_FLUSHREAD
whenever the read queue for the terminal is flushed.
.It Dv TIOCPKT_FLUSHWRITE
whenever the write queue for the terminal is flushed.
.It Dv TIOCPKT_STOP
whenever output to the terminal is stopped a la
.Ql ^S .
.It Dv TIOCPKT_START
whenever output to the terminal is restarted.
.It Dv TIOCPKT_DOSTOP
whenever
.Dv VSTOP
is
.Ql ^S
and
.Dv VSTART
is
.Ql ^Q .
.It Dv TIOCPKT_NOSTOP
whenever the start and stop characters are not
.Ql ^S/^Q .
.El
.Pp
While this mode is in use, the presence of control status information
to be read from the master side may be detected by a
.Xr select 2
for exceptional conditions.
.Pp
This mode is used by
.Xr rlogin 1
and
.Xr rlogind 8
to implement a remote-echoed, locally
.Ql ^S/^Q
flow-controlled
remote login with proper back-flushing of output; it can be
used by other similar programs.
.It Dv TIOCGPTN
Obtain device unit number, which can be used to generate the filename of
the pseudo-terminal slave device.
This
.Xr ioctl 2
should not be used directly.
Instead, the
.Xr ptsname 3
function should be used.
.It Dv TIOCPTMASTER
Determine whether the file descriptor is pointing to a pseudo-terminal
master device.
This
.Xr ioctl 2
should not be used directly.
It is used to implement routines like
.Xr grantpt 3 .
.El
.Sh FILES
The files used by this
pseudo-terminals implementation are:
.Bl -tag -width ".Pa /dev/pts/[num]"
.It Pa /dev/pts/[num]
Pseudo-terminal slave devices.
.El
.Sh DIAGNOSTICS
None.
.Sh SEE ALSO
.Xr posix_openpt 2 ,
.Xr grantpt 3 ,
.Xr ptsname 3 ,
.Xr pty 4 ,
.Xr tty 4
.Sh HISTORY
A
pseudo-terminal driver appeared in
.Bx 4.2 .
In
.Fx 8.0 ,
it was replaced with the
.Nm
driver.