[apple/xnu.git] / bsd / man / man4 / pty.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. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 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.
.\"
.\"     @(#)pty.4	8.2 (Berkeley) 11/30/93
.\"
.Dd November 30, 1993
.Dt PTY 4
.Os BSD 4.2
.Sh NAME
.Nm pty
.Nd pseudo terminal driver
.Sh SYNOPSIS
.Cd "pseudo-device pty" Op Ar count
.Sh DESCRIPTION
The
.Nm pty
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
In configuring, if an optional
.Ar count
is given in
the specification, that number of pseudo terminal pairs are configured;
the default count is 32.
.Pp
The following 
.Xr ioctl 2
calls apply only to pseudo terminals:
.Bl -tag -width TIOCREMOTE
.It Dv TIOCSTOP
Stops output to a terminal (e.g. like typing
.Ql ^S ) .
Takes
no parameter.
.It Dv TIOCSTART
Restarts output (stopped by
.Dv TIOCSTOP
or by typing
.Ql ^S ) .
Takes no parameter.
.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 
.Em t_stopc
is
.Ql ^S
and 
.Em t_startc
is
.Ql ^Q .
.It Dv TIOCPKT_NOSTOP
whenever the start and stop characters are not
.Ql ^S/^Q .
.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.
.El
.It Dv TIOCUCNTL
Enable/disable a mode that allows a small number of simple user
.Xr ioctl 2
commands to be passed through the pseudo-terminal,
using a protocol similar to that of
.Dv TIOCPKT .
The
.Dv TIOCUCNTL
and
.Dv TIOCPKT
modes are mutually exclusive.
This mode is enabled from the master side of a pseudo terminal
by specifying (by reference)
a nonzero parameter and disabled by specifying (by reference)
a zero parameter.
Each subsequent 
.Xr read 2
from the master side will return data written on the slave part of
the pseudo terminal preceded by a zero byte,
or a single byte reflecting a user control operation on the slave side.
A user control command consists of a special
.Xr ioctl 2
operation with no data; the command is given as
.Dv UIOCCMD Ns (n) ,
where
.Ar n
is a number in the range 1-255.
The operation value
.Ar n
will be received as a single byte on the next
.Xr read 2
from the master side.
The
.Xr ioctl 2
.Dv UIOCCMD Ns (0)
is a no-op that may be used to probe for
the existence of this facility.
As with
.Dv TIOCPKT
mode, command operations may be detected with a
.Xr select 2
for exceptional conditions.
.It Dv TIOCREMOTE
A mode for the master half of a pseudo terminal, independent
of
.Dv TIOCPKT .
This mode causes input to the pseudo terminal
to be flow controlled and not input edited (regardless of the
terminal mode).  Each write to the control terminal produces
a record boundary for the process reading the terminal.  In
normal usage, a write of data is like the data typed as a line
on the terminal; a write of 0 bytes is like typing an end-of-file
character.
.Dv TIOCREMOTE
can be used when doing remote line
editing in a window manager, or whenever flow controlled input
is required.
.El
.Sh FILES
.Bl -tag -width /dev/tty[p-sP-S][a-z0-9]x -compact
.It Pa /dev/pty[p-sP-S][a-z0-9]
master pseudo terminals
.It Pa /dev/tty[p-sP-S][a-z0-9]
slave pseudo terminals
.El
.Sh DIAGNOSTICS
None.
.Sh HISTORY
The
.Nm
driver appeared in
.Bx 4.2 .
Commit	Line	Data
9bccf70c A	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	.\"
	34	.Dd November 30, 1993
	35	.Dt PTY 4
	36	.Os BSD 4.2
	37	.Sh NAME
	38	.Nm pty
	39	.Nd pseudo terminal driver
	40	.Sh SYNOPSIS
	41	.Cd "pseudo-device pty" Op Ar count
	42	.Sh DESCRIPTION
	43	The
	44	.Nm pty
	45	driver provides support for a device-pair termed a
	46	.Em pseudo terminal .
	47	A pseudo terminal is a pair of character devices, a
	48	.Em master
	49	device and a
	50	.Em slave
	51	device. The slave device provides to a process
	52	an interface identical
	53	to that described in
	54	.Xr tty 4 .
	55	However, whereas all other devices which provide the
	56	interface described in
	57	.Xr tty 4
	58	have a hardware device of some sort behind them, the slave
	59	device has, instead, another process manipulating
	60	it through the master half of the pseudo terminal.
	61	That is, anything written on the master device is
	62	given to the slave device as input and anything written
	63	on the slave device is presented as input on the master
	64	device.
65	.Pp
66	In configuring, if an optional
67	.Ar count
68	is given in
69	the specification, that number of pseudo terminal pairs are configured;
70	the default count is 32.
71	.Pp
72	The following
73	.Xr ioctl 2
74	calls apply only to pseudo terminals:
75	.Bl -tag -width TIOCREMOTE
76	.It Dv TIOCSTOP
77	Stops output to a terminal (e.g. like typing
78	.Ql ^S ) .
79	Takes
80	no parameter.
81	.It Dv TIOCSTART
82	Restarts output (stopped by
83	.Dv TIOCSTOP
84	or by typing
85	.Ql ^S ) .
86	Takes no parameter.
87	.It Dv TIOCPKT
88	Enable/disable
89	.Em packet
90	mode. Packet mode is enabled by specifying (by reference)
91	a nonzero parameter and disabled by specifying (by reference)
92	a zero parameter. When applied to the master side of a pseudo
93	terminal, each subsequent
94	.Xr read 2
95	from the terminal will return data written on the slave part of
96	the pseudo terminal preceded by a zero byte (symbolically
97	defined as
98	.Dv TIOCPKT_DATA ) ,
99	or a single byte reflecting control
100	status information. In the latter case, the byte is an inclusive-or
101	of zero or more of the bits:
102	.Bl -tag -width TIOCPKT_FLUSHWRITE
103	.It Dv TIOCPKT_FLUSHREAD
104	whenever the read queue for the terminal is flushed.
105	.It Dv TIOCPKT_FLUSHWRITE
106	whenever the write queue for the terminal is flushed.
107	.It Dv TIOCPKT_STOP
108	whenever output to the terminal is stopped a la
109	.Ql ^S .
110	.It Dv TIOCPKT_START
111	whenever output to the terminal is restarted.
112	.It Dv TIOCPKT_DOSTOP
113	whenever
114	.Em t_stopc
115	is
116	.Ql ^S
117	and
118	.Em t_startc
119	is
120	.Ql ^Q .
121	.It Dv TIOCPKT_NOSTOP
122	whenever the start and stop characters are not
123	.Ql ^S/^Q .
124	.Pp
125	While this mode is in use, the presence of control status information
126	to be read from the master side may be detected by a
127	.Xr select 2
128	for exceptional conditions.
129	.Pp
130	This mode is used by
131	.Xr rlogin 1
132	and
133	.Xr rlogind 8
134	to implement a remote-echoed, locally
135	.Ql ^S/^Q
136	flow-controlled
137	remote login with proper back-flushing of output; it can be
138	used by other similar programs.
139	.El
140	.It Dv TIOCUCNTL
141	Enable/disable a mode that allows a small number of simple user
142	.Xr ioctl 2
143	commands to be passed through the pseudo-terminal,
144	using a protocol similar to that of
145	.Dv TIOCPKT .
146	The
147	.Dv TIOCUCNTL
148	and
149	.Dv TIOCPKT
150	modes are mutually exclusive.
151	This mode is enabled from the master side of a pseudo terminal
152	by specifying (by reference)
153	a nonzero parameter and disabled by specifying (by reference)
154	a zero parameter.
155	Each subsequent
156	.Xr read 2
157	from the master side will return data written on the slave part of
158	the pseudo terminal preceded by a zero byte,
159	or a single byte reflecting a user control operation on the slave side.
160	A user control command consists of a special
161	.Xr ioctl 2
162	operation with no data; the command is given as
163	.Dv UIOCCMD Ns (n) ,
164	where
165	.Ar n
166	is a number in the range 1-255.
167	The operation value
168	.Ar n
169	will be received as a single byte on the next
170	.Xr read 2
171	from the master side.
172	The
173	.Xr ioctl 2
174	.Dv UIOCCMD Ns (0)
175	is a no-op that may be used to probe for
176	the existence of this facility.
177	As with
178	.Dv TIOCPKT
179	mode, command operations may be detected with a
180	.Xr select 2
181	for exceptional conditions.
182	.It Dv TIOCREMOTE
183	A mode for the master half of a pseudo terminal, independent
184	of
185	.Dv TIOCPKT .
186	This mode causes input to the pseudo terminal
187	to be flow controlled and not input edited (regardless of the
188	terminal mode). Each write to the control terminal produces
189	a record boundary for the process reading the terminal. In
190	normal usage, a write of data is like the data typed as a line
191	on the terminal; a write of 0 bytes is like typing an end-of-file
192	character.
193	.Dv TIOCREMOTE
194	can be used when doing remote line
195	editing in a window manager, or whenever flow controlled input
196	is required.
197	.El
198	.Sh FILES
199	.Bl -tag -width /dev/tty[p-sP-S][a-z0-9]x -compact
200	.It Pa /dev/pty[p-sP-S][a-z0-9]
201	master pseudo terminals
202	.It Pa /dev/tty[p-sP-S][a-z0-9]
203	slave pseudo terminals
204	.El
205	.Sh DIAGNOSTICS
206	None.
207	.Sh HISTORY
208	The
209	.Nm
210	driver appeared in
211	.Bx 4.2 .