[unix-history] / usr / src / share / man / man4 / pty.4

.\" Copyright (c) 1983 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)pty.4	6.1 (Berkeley) %G%
.\"
.TH PTY 4 ""
.UC 5
.SH NAME
pty \- pseudo terminal driver
.SH SYNOPSIS
.B pseudo-device pty
.SH DESCRIPTION
The
.I pty
driver provides support for a device-pair termed a
.IR "pseudo terminal" .
A pseudo terminal is a pair of character devices, a
.I master
device and a
.I slave
device.  The slave device provides processes
an interface identical
to that described in
.IR tty (4).
However, whereas all other devices which provide the 
interface described in
.IR 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 no optional ``count'' is given in
the specification, 16 pseudo terminal pairs are configured.
.PP
The following 
.I ioctl
calls apply only to pseudo terminals:
.TP
TIOCSTOP
Stops output to a terminal (e.g. like typing ^S).  Takes
no parameter.
.TP
TIOCSTART
Restarts output (stopped by TIOCSTOP or by typing ^S).
Takes no parameter.
.TP
TIOCPKT
Enable/disable 
.I 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 
.I read 
from the terminal will return data written on the slave part of
the pseudo terminal preceded by a zero byte (symbolically
defined as 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:
.RS
.TP
TIOCPKT_FLUSHREAD
whenever the read queue for the terminal is flushed.
.TP
TIOCPKT_FLUSHWRITE
whenever the write queue for the terminal is flushed.
.TP
TIOCPKT_STOP
whenever output to the terminal is stopped a la ^S.
.TP
TIOCPKT_START
whenever output to the terminal is restarted.
.TP
TIOCPKT_DOSTOP
whenever 
.I t_stopc
is ^S
and 
.I t_startc
is ^Q.
.TP
TIOCPKT_NOSTOP
whenever the start and stop characters are not ^S/^Q.
.RE
.IP
This mode is used by
.IR rlogin (1C)
and
.IR rlogind (8C)
to implement a remote-echoed, locally ^S/^Q flow-controlled
remote login with proper back-flushing of output; it can be
used by other similar programs.
.TP
TIOCREMOTE
A mode for the master half of a pseudo terminal, independent
of 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.  TIOCREMOTE can be used when doing remote line
editing in a window manager, or whenever flow controlled input
is required.
.SH FILES
.DT
/dev/pty[p-r][0-9a-f]	master pseudo terminals
.br
/dev/tty[p-r][0-9a-f]	slave pseudo terminals
.SH DIAGNOSTICS
None.
.SH BUGS
It is not possible to send an EOT.
Commit	Line	Data
16b5b9ce KM	1	.\" Copyright (c) 1983 Regents of the University of California.
	2	.\" All rights reserved. The Berkeley software License Agreement
	3	.\" specifies the terms and conditions for redistribution.
	4	.\"
260e89d5	5	.\" @(#)pty.4 6.1 (Berkeley) %G%
16b5b9ce	6	.\"
260e89d5	7	.TH PTY 4 ""
16b5b9ce KM	8	.UC 5
	9	.SH NAME
	10	pty \- pseudo terminal driver
	11	.SH SYNOPSIS
	12	.B pseudo-device pty
	13	.SH DESCRIPTION
	14	The
	15	.I pty
	16	driver provides support for a device-pair termed a
	17	.IR "pseudo terminal" .
	18	A pseudo terminal is a pair of character devices, a
	19	.I master
	20	device and a
	21	.I slave
	22	device. The slave device provides processes
	23	an interface identical
	24	to that described in
	25	.IR tty (4).
	26	However, whereas all other devices which provide the
	27	interface described in
	28	.IR tty (4)
	29	have a hardware device of some sort behind them, the slave
	30	device has, instead, another process manipulating
	31	it through the master half of the pseudo terminal.
	32	That is, anything written on the master device is
	33	given to the slave device as input and anything written
	34	on the slave device is presented as input on the master
	35	device.
	36	.PP
	37	In configuring, if no optional ``count'' is given in
	38	the specification, 16 pseudo terminal pairs are configured.
	39	.PP
	40	The following
	41	.I ioctl
	42	calls apply only to pseudo terminals:
	43	.TP
	44	TIOCSTOP
	45	Stops output to a terminal (e.g. like typing ^S). Takes
	46	no parameter.
	47	.TP
	48	TIOCSTART
	49	Restarts output (stopped by TIOCSTOP or by typing ^S).
	50	Takes no parameter.
	51	.TP
	52	TIOCPKT
	53	Enable/disable
	54	.I packet
	55	mode. Packet mode is enabled by specifying (by reference)
	56	a nonzero parameter and disabled by specifying (by reference)
	57	a zero parameter. When applied to the master side of a pseudo
	58	terminal, each subsequent
	59	.I read
	60	from the terminal will return data written on the slave part of
	61	the pseudo terminal preceded by a zero byte (symbolically
	62	defined as TIOCPKT_DATA), or a single byte reflecting control
	63	status information. In the latter case, the byte is an inclusive-or
	64	of zero or more of the bits:
	65	.RS
	66	.TP
	67	TIOCPKT_FLUSHREAD
	68	whenever the read queue for the terminal is flushed.
	69	.TP
	70	TIOCPKT_FLUSHWRITE
	71	whenever the write queue for the terminal is flushed.
72	.TP
73	TIOCPKT_STOP
74	whenever output to the terminal is stopped a la ^S.
75	.TP
76	TIOCPKT_START
77	whenever output to the terminal is restarted.
78	.TP
79	TIOCPKT_DOSTOP
80	whenever
81	.I t_stopc
82	is ^S
83	and
84	.I t_startc
85	is ^Q.
86	.TP
87	TIOCPKT_NOSTOP
88	whenever the start and stop characters are not ^S/^Q.
89	.RE
90	.IP
91	This mode is used by
92	.IR rlogin (1C)
93	and
94	.IR rlogind (8C)
95	to implement a remote-echoed, locally ^S/^Q flow-controlled
96	remote login with proper back-flushing of output; it can be
97	used by other similar programs.
98	.TP
99	TIOCREMOTE
100	A mode for the master half of a pseudo terminal, independent
101	of TIOCPKT. This mode causes input to the pseudo terminal
102	to be flow controlled and not input edited (regardless of the
103	terminal mode). Each write to the control terminal produces
104	a record boundary for the process reading the terminal. In
105	normal usage, a write of data is like the data typed as a line
106	on the terminal; a write of 0 bytes is like typing an end-of-file
107	character. TIOCREMOTE can be used when doing remote line
108	editing in a window manager, or whenever flow controlled input
109	is required.
110	.SH FILES
111	.DT
112	/dev/pty[p-r][0-9a-f] master pseudo terminals
113	.br
114	/dev/tty[p-r][0-9a-f] slave pseudo terminals
115	.SH DIAGNOSTICS
116	None.
117	.SH BUGS
118	It is not possible to send an EOT.