]> git.saurik.com Git - apple/xnu.git/blob - bsd/man/man4/tty.4
xnu-3789.70.16.tar.gz
[apple/xnu.git] / bsd / man / man4 / tty.4
1 .\" Copyright (c) 1991, 1992, 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 .\" @(#)tty.4 8.3 (Berkeley) 4/19/94
33 .\" $FreeBSD$
34 .\"
35 .Dd August 14, 1992
36 .Dt TTY 4
37 .Os BSD 4
38 .Sh NAME
39 .Nm tty
40 .Nd general terminal interface
41 .Sh SYNOPSIS
42 .Fd #include <sys/ioctl.h>
43 .Sh DESCRIPTION
44 This section describes the interface to the terminal drivers
45 in the system.
46 .Ss Terminal Special Files
47 Each hardware terminal port on the system usually has a terminal special device
48 file associated with it in the directory ``/dev/'' (for
49 example, ``/dev/tty03'').
50 When a user logs into
51 the system on one of these hardware terminal ports, the system has already
52 opened the associated device and prepared the line for normal interactive
53 use (see
54 .Xr getty 8 .)
55 There is also a special case of a terminal file that connects not to
56 a hardware terminal port, but to another program on the other side.
57 These special terminal devices are called
58 .Em ptys
59 and provide the mechanism necessary to give users the same interface to the
60 system when logging in over a network (using
61 .Xr rlogin 1 ,
62 or
63 .Xr telnet 1
64 for example). Even in these cases the details of how the terminal
65 file was opened and set up is already handled by special software
66 in the system.
67 Thus, users do not normally need to worry about the details of
68 how these lines are opened or used. Also, these lines are often used
69 for dialing out of a system (through an out-calling modem), but again
70 the system provides programs that hide the details of accessing
71 these terminal special files (see
72 .Xr tip 1 ).
73 .Pp
74 When an interactive user logs in, the system prepares the line to
75 behave in a certain way (called a
76 .Em "line discipline" ) ,
77 the particular details of which is described in
78 .Xr stty 1
79 at the command level, and in
80 .Xr termios 4
81 at the programming level. A user may be concerned with changing
82 settings associated with his particular login terminal and should refer
83 to the preceding man pages for the common cases. The remainder of
84 this man page is concerned
85 with describing details of using and controlling terminal devices
86 at a low level, such as that possibly required by a program wishing
87 to provide features similar to those provided by the system.
88 .Ss Line disciplines
89 A terminal file is used like any other file in the system in that
90 it can be opened, read, and written to using standard system
91 calls. For each existing terminal file, there is a software processing module
92 called a
93 .Em "line discipline"
94 is associated with it. The
95 .Em "line discipline"
96 essentially glues the low level device driver code with the high
97 level generic interface routines (such as
98 .Xr read 2
99 and
100 .Xr write 2 ),
101 and is responsible for implementing the semantics associated
102 with the device. When a terminal file is first opened by a program,
103 the default
104 .Em "line discipline"
105 called the
106 .Dv termios
107 line discipline is associated with the file. This is the primary
108 line discipline that is used in most cases and provides the semantics
109 that users normally associate with a terminal. When the
110 .Dv termios
111 line discipline is in effect, the terminal file behaves and is
112 operated according to the rules described in
113 .Xr termios 4 .
114 Please refer to that man page for a full description of the terminal
115 semantics.
116 The operations described here
117 generally represent features common
118 across all
119 .Em "line disciplines" ,
120 however some of these calls may not
121 make sense in conjunction with a line discipline other than
122 .Dv termios ,
123 and some may not be supported by the underlying
124 hardware (or lack thereof, as in the case of ptys).
125 .Ss Terminal File Operations
126 All of the following operations are invoked using the
127 .Xr ioctl 2
128 system call. Refer to that man page for a description of
129 the
130 .Em request
131 and
132 .Em argp
133 parameters.
134 In addition to the ioctl
135 .Em requests
136 defined here, the specific line discipline
137 in effect will define other
138 .Em requests
139 specific to it (actually
140 .Xr termios 4
141 defines them as function calls, not ioctl
142 .Em requests . )
143 The following section lists the available ioctl requests. The
144 name of the request, a description of its purpose, and the typed
145 .Em argp
146 parameter (if any)
147 are listed. For example, the first entry says
148 .Pp
149 .D1 Em "TIOCSETD int *ldisc"
150 .Pp
151 and would be called on the terminal associated with
152 file descriptor zero by the following code fragment:
153 .Bd -literal
154 int ldisc;
155
156 ldisc = TTYDISC;
157 ioctl(0, TIOCSETD, &ldisc);
158 .Ed
159 .Ss Terminal File Request Descriptions
160 .Bl -tag -width TIOCGWINSZ
161 .It Dv TIOCSETD Fa int *ldisc
162 Change to the new line discipline pointed to by
163 .Fa ldisc .
164 The available line disciplines are listed in
165 .Pa Aq sys/ttycom.h
166 and currently are:
167 .Pp
168 .Bl -tag -width TIOCGWINSZ -compact
169 .It TTYDISC
170 Termios interactive line discipline.
171 .It TABLDISC
172 Tablet line discipline.
173 .It SLIPDISC
174 Serial IP line discipline.
175 .It PPPDISC
176 PPP line discipline.
177 .El
178 .Pp
179 .It Dv TIOCGETD Fa int *ldisc
180 Return the current line discipline in the integer pointed to by
181 .Fa ldisc .
182 .It Dv TIOCSBRK Fa void
183 Set the terminal hardware into BREAK condition.
184 .It Dv TIOCCBRK Fa void
185 Clear the terminal hardware BREAK condition.
186 .It Dv TIOCSDTR Fa void
187 Assert data terminal ready (DTR).
188 .It Dv TIOCCDTR Fa void
189 Clear data terminal ready (DTR).
190 .It Dv TIOCGPGRP Fa int *tpgrp
191 Return the current process group the terminal is associated
192 with in the integer pointed to by
193 .Fa tpgrp .
194 This is the underlying call that implements the
195 .Xr termios 4
196 .Fn tcgetattr
197 call.
198 .It Dv TIOCSPGRP Fa int *tpgrp
199 Associate the terminal with the process group (as an integer) pointed to by
200 .Fa tpgrp .
201 This is the underlying call that implements the
202 .Xr termios 4
203 .Fn tcsetattr
204 call.
205 .It Dv TIOCGETA Fa struct termios *term
206 Place the current value of the termios state associated with the
207 device in the termios structure pointed to by
208 .Fa term .
209 This is the underlying call that implements the
210 .Xr termios 4
211 .Fn tcgetattr
212 call.
213 .It Dv TIOCSETA Fa struct termios *term
214 Set the termios state associated with the device immediately.
215 This is the underlying call that implements the
216 .Xr termios 4
217 .Fn tcsetattr
218 call with the
219 .Dv TCSANOW
220 option.
221 .It Dv TIOCSETAW Fa struct termios *term
222 First wait for any output to complete, then set the termios state
223 associated with the device.
224 This is the underlying call that implements the
225 .Xr termios 4
226 .Fn tcsetattr
227 call with the
228 .Dv TCSADRAIN
229 option.
230 .It Dv TIOCSETAF Fa struct termios *term
231 First wait for any output to complete, clear any pending input,
232 then set the termios state associated with the device.
233 This is the underlying call that implements the
234 .Xr termios 4
235 .Fn tcsetattr
236 call with the
237 .Dv TCSAFLUSH
238 option.
239 .It Dv TIOCOUTQ Fa int *num
240 Place the current number of characters in the output queue in the
241 integer pointed to by
242 .Fa num .
243 .It Dv TIOCSTI Fa char *cp
244 Simulate typed input. Pretend as if the terminal received the
245 character pointed to by
246 .Fa cp .
247 .It Dv TIOCNOTTY Fa void
248 This call is obsolete but left for compatibility. In the past, when
249 a process that didn't have a controlling terminal (see
250 .Em The Controlling Terminal
251 in
252 .Xr termios 4 )
253 first opened a terminal device, it acquired that terminal as its
254 controlling terminal. For some programs this was a hazard as they
255 didn't want a controlling terminal in the first place, and this
256 provided a mechanism to disassociate the controlling terminal from
257 the calling process. It
258 .Em must
259 be called by opening the file
260 .Pa /dev/tty
261 and calling
262 .Dv TIOCNOTTY
263 on that file descriptor.
264 .Pp
265 The current system does not allocate a controlling terminal to
266 a process on an
267 .Fn open
268 call: there is a specific ioctl called
269 .Dv TIOSCTTY
270 to make a terminal the controlling
271 terminal.
272 In addition, a program can
273 .Fn fork
274 and call the
275 .Fn setsid
276 system call which will place the process into its own session - which
277 has the effect of disassociating it from the controlling terminal. This
278 is the new and preferred method for programs to lose their controlling
279 terminal.
280 .It Dv TIOCSTOP Fa void
281 Stop output on the terminal (like typing ^S at the keyboard).
282 .It Dv TIOCSTART Fa void
283 Start output on the terminal (like typing ^Q at the keyboard).
284 .It Dv TIOCSCTTY Fa void
285 Make the terminal the controlling terminal for the process (the process
286 must not currently have a controlling terminal).
287 .It Dv TIOCDRAIN Fa void
288 Wait until all output is drained.
289 .It Dv TIOCEXCL Fa void
290 Set exclusive use on the terminal. No further opens are permitted
291 except by root. Of course, this means that programs that are run by
292 root (or setuid) will not obey the exclusive setting - which limits
293 the usefulness of this feature.
294 .It Dv TIOCNXCL Fa void
295 Clear exclusive use of the terminal. Further opens are permitted.
296 .It Dv TIOCFLUSH Fa int *what
297 If the value of the int pointed to by
298 .Fa what
299 contains the
300 .Dv FREAD
301 bit as defined in
302 .Pa Aq sys/file.h ,
303 then all characters in the input queue are cleared. If it contains
304 the
305 .Dv FWRITE
306 bit, then all characters in the output queue are cleared. If the
307 value of the integer is zero, then it behaves as if both the
308 .Dv FREAD
309 and
310 .Dv FWRITE
311 bits were set (i.e. clears both queues).
312 .It Dv TIOCGWINSZ Fa struct winsize *ws
313 Put the window size information associated with the terminal in the
314 .Va winsize
315 structure pointed to by
316 .Fa ws .
317 The window size structure contains the number of rows and columns (and pixels
318 if appropriate) of the devices attached to the terminal. It is set by user software
319 and is the means by which most full\&-screen oriented programs determine the
320 screen size. The
321 .Va winsize
322 structure is defined in
323 .Pa Aq sys/ioctl.h .
324 .It Dv TIOCSWINSZ Fa struct winsize *ws
325 Set the window size associated with the terminal to be the value in
326 the
327 .Va winsize
328 structure pointed to by
329 .Fa ws
330 (see above).
331 .It Dv TIOCCONS Fa int *on
332 If
333 .Fa on
334 points to a non-zero integer, redirect kernel console output (kernel printf's)
335 to this terminal.
336 If
337 .Fa on
338 points to a zero integer, redirect kernel console output back to the normal
339 console. This is usually used on workstations to redirect kernel messages
340 to a particular window.
341 .It Dv TIOCMSET Fa int *state
342 The integer pointed to by
343 .Fa state
344 contains bits that correspond to modem state. Following is a list
345 of defined variables and the modem state they represent:
346 .Pp
347 .Bl -tag -width TIOCMXCTS -compact
348 .It TIOCM_LE
349 Line Enable.
350 .It TIOCM_DTR
351 Data Terminal Ready.
352 .It TIOCM_RTS
353 Request To Send.
354 .It TIOCM_ST
355 Secondary Transmit.
356 .It TIOCM_SR
357 Secondary Receive.
358 .It TIOCM_CTS
359 Clear To Send.
360 .It TIOCM_CAR
361 Carrier Detect.
362 .It TIOCM_CD
363 Carrier Detect (synonym).
364 .It TIOCM_RNG
365 Ring Indication.
366 .It TIOCM_RI
367 Ring Indication (synonym).
368 .It TIOCM_DSR
369 Data Set Ready.
370 .El
371 .Pp
372 This call sets the terminal modem state to that represented by
373 .Fa state .
374 Not all terminals may support this.
375 .It Dv TIOCMGET Fa int *state
376 Return the current state of the terminal modem lines as represented
377 above in the integer pointed to by
378 .Fa state .
379 .It Dv TIOCMBIS Fa int *state
380 The bits in the integer pointed to by
381 .Fa state
382 represent modem state as described above, however the state is OR-ed
383 in with the current state.
384 .It Dv TIOCMBIC Fa int *state
385 The bits in the integer pointed to by
386 .Fa state
387 represent modem state as described above, however each bit which is on
388 in
389 .Fa state
390 is cleared in the terminal.
391 .El
392 .Sh SEE ALSO
393 .Xr stty 1 ,
394 .Xr ioctl 2 ,
395 .Xr pty 4 ,
396 .Xr termios 4 ,
397 .Xr getty 8