1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)pty.4 8.2 (Berkeley) 11/30/93 33.\" $FreeBSD: src/share/man/man4/pty.4,v 1.8.2.3 2001/08/17 13:08:39 ru Exp $ 34.\" $DragonFly: src/share/man/man4/pty.4,v 1.2 2003/06/17 04:36:59 dillon Exp $ 35.\" 36.Dd November 30, 1993 37.Dt PTY 4 38.Os 39.Sh NAME 40.Nm pty 41.Nd pseudo terminal driver 42.Sh SYNOPSIS 43.Cd "pseudo-device pty" 44.Sh DESCRIPTION 45The 46.Nm 47driver provides support for a device-pair termed a 48.Em pseudo terminal . 49A pseudo terminal is a pair of character devices, a 50.Em master 51device and a 52.Em slave 53device. The slave device provides to a process 54an interface identical 55to that described in 56.Xr tty 4 . 57However, whereas all other devices which provide the 58interface described in 59.Xr tty 4 60have a hardware device of some sort behind them, the slave 61device has, instead, another process manipulating 62it through the master half of the pseudo terminal. 63That is, anything written on the master device is 64given to the slave device as input and anything written 65on the slave device is presented as input on the master 66device. 67.Pp 68The following 69.Xr ioctl 2 70calls apply only to pseudo terminals: 71.Bl -tag -width ".Dv TIOCREMOTE" 72.It Dv TIOCSTOP 73Stops output to a terminal (e.g. like typing 74.Ql ^S ) . 75Takes 76no parameter. 77.It Dv TIOCSTART 78Restarts output (stopped by 79.Dv TIOCSTOP 80or by typing 81.Ql ^S ) . 82Takes no parameter. 83.It Dv TIOCPKT 84Enable/disable 85.Em packet 86mode. Packet mode is enabled by specifying (by reference) 87a nonzero parameter and disabled by specifying (by reference) 88a zero parameter. When applied to the master side of a pseudo 89terminal, each subsequent 90.Xr read 2 91from the terminal will return data written on the slave part of 92the pseudo terminal preceded by a zero byte (symbolically 93defined as 94.Dv TIOCPKT_DATA ) , 95or a single byte reflecting control 96status information. In the latter case, the byte is an inclusive-or 97of zero or more of the bits: 98.Bl -tag -width TIOCPKT_FLUSHWRITE 99.It Dv TIOCPKT_FLUSHREAD 100whenever the read queue for the terminal is flushed. 101.It Dv TIOCPKT_FLUSHWRITE 102whenever the write queue for the terminal is flushed. 103.It Dv TIOCPKT_STOP 104whenever output to the terminal is stopped a la 105.Ql ^S . 106.It Dv TIOCPKT_START 107whenever output to the terminal is restarted. 108.It Dv TIOCPKT_DOSTOP 109whenever 110.Em t_stopc 111is 112.Ql ^S 113and 114.Em t_startc 115is 116.Ql ^Q . 117.It Dv TIOCPKT_NOSTOP 118whenever the start and stop characters are not 119.Ql ^S/^Q . 120.Pp 121While this mode is in use, the presence of control status information 122to be read from the master side may be detected by a 123.Xr select 2 124for exceptional conditions. 125.Pp 126This mode is used by 127.Xr rlogin 1 128and 129.Xr rlogind 8 130to implement a remote-echoed, locally 131.Ql ^S/^Q 132flow-controlled 133remote login with proper back-flushing of output; it can be 134used by other similar programs. 135.El 136.It Dv TIOCUCNTL 137Enable/disable a mode that allows a small number of simple user 138.Xr ioctl 2 139commands to be passed through the pseudo-terminal, 140using a protocol similar to that of 141.Dv TIOCPKT . 142The 143.Dv TIOCUCNTL 144and 145.Dv TIOCPKT 146modes are mutually exclusive. 147This mode is enabled from the master side of a pseudo terminal 148by specifying (by reference) 149a nonzero parameter and disabled by specifying (by reference) 150a zero parameter. 151Each subsequent 152.Xr read 2 153from the master side will return data written on the slave part of 154the pseudo terminal preceded by a zero byte, 155or a single byte reflecting a user control operation on the slave side. 156A user control command consists of a special 157.Xr ioctl 2 158operation with no data; the command is given as 159.Dv UIOCCMD Ns (n) , 160where 161.Ar n 162is a number in the range 1-255. 163The operation value 164.Ar n 165will be received as a single byte on the next 166.Xr read 2 167from the master side. 168The 169.Xr ioctl 2 170.Dv UIOCCMD Ns (0) 171is a no-op that may be used to probe for 172the existence of this facility. 173As with 174.Dv TIOCPKT 175mode, command operations may be detected with a 176.Xr select 2 177for exceptional conditions. 178.It Dv TIOCREMOTE 179A mode for the master half of a pseudo terminal, independent 180of 181.Dv TIOCPKT . 182This mode causes input to the pseudo terminal 183to be flow controlled and not input edited (regardless of the 184terminal mode). Each write to the control terminal produces 185a record boundary for the process reading the terminal. In 186normal usage, a write of data is like the data typed as a line 187on the terminal; a write of 0 bytes is like typing an end-of-file 188character. 189.Dv TIOCREMOTE 190can be used when doing remote line 191editing in a window manager, or whenever flow controlled input 192is required. 193.El 194.Sh FILES 195.Bl -tag -width /dev/tty[p-sP-S][0-9a-v]x -compact 196.It Pa /dev/pty[p-sP-S][0-9a-v] 197master pseudo terminals 198.It Pa /dev/tty[p-sP-S][0-9a-v] 199slave pseudo terminals 200.El 201.Sh DIAGNOSTICS 202None. 203.Sh SEE ALSO 204.Xr tty 4 205.Sh HISTORY 206The 207.Nm 208driver appeared in 209.Bx 4.2 . 210