1.\" $NetBSD: tty.4,v 1.22 2003/08/07 10:31:04 agc Exp $ 2.\" 3.\" Copyright (c) 1991, 1992, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)tty.4 8.3 (Berkeley) 4/19/94 31.\" 32.Dd August 14, 1992 33.Dt TTY 4 34.Os 35.Sh NAME 36.Nm tty 37.Nd general terminal interface 38.Sh SYNOPSIS 39.In sys/ioctl.h 40.Sh DESCRIPTION 41This section describes the interface to the terminal drivers 42in the system. 43.Ss Terminal Special Files 44Each hardware terminal port on the system usually has two terminal special 45device files associated with it in the directory 46.Pa /dev/ 47(for example, 48.Pa /dev/tty03 49and 50.Pa /dev/dty03 ) . 51.Pp 52The 53.Pa /dev/ttyXX 54special file is used for dial-in modems and terminals. 55When a user logs into 56the system on one of these hardware terminal ports, the system has already 57opened the associated device and prepared the line for normal interactive 58use (see 59.Xr getty 8 ) . 60.Pp 61The 62.Pa /dev/dtyXX 63special file is a SunOS-compatible dial-out device. Unlike 64the dial-in device, opening the dial-out device never blocks. If the 65corresponding dial-in device is already opened (not blocked in the open waiting 66for carrier), then the dial-out open will fail immediately; otherwise it will 67succeed immediately. While the dial-out device is open, the dial-in device may 68not be opened. If the dial-in open is blocking, it will wait until the dial-out 69device is closed (and carrier is detected); otherwise it will fail immediately. 70.Pp 71There is also a special case of a terminal file that connects not to 72a hardware terminal port, but to another program on the other side. 73These special terminal devices are called 74.Em ptys 75and provide the mechanism necessary to give users the same interface to the 76system when logging in over a network (using 77.Xr rlogin 1 , 78or 79.Xr telnet 1 80for example.) Even in these cases the details of how the terminal 81file was opened and set up is already handled by special software 82in the system. 83Thus, users do not normally need to worry about the details of 84how these lines are opened or used. Also, these lines are often used 85for dialing out of a system (through an out-calling modem), but again 86the system provides programs that hide the details of accessing 87these terminal special files (see 88.Xr tip 1 ) . 89.Pp 90When an interactive user logs in, the system prepares the line to 91behave in a certain way (called a 92.Em line discipline ) , 93the particular details of which is described in 94.Xr stty 1 95at the command level, and in 96.Xr termios 4 97at the programming level. A user may be concerned with changing 98settings associated with his particular login terminal and should refer 99to the preceding man pages for the common cases. The remainder of 100this man page is concerned 101with describing details of using and controlling terminal devices 102at a low level, such as that possibly required by a program wishing 103to provide features similar to those provided by the system. 104.Ss Line disciplines 105A terminal file is used like any other file in the system in that 106it can be opened, read, and written to using standard system 107calls. For each existing terminal file, there is a software processing module 108called a 109.Em line discipline 110associated with it. The 111.Em line discipline 112essentially glues the low level device driver code with the high 113level generic interface routines (such as 114.Xr read 2 115and 116.Xr write 2 ) , 117and is responsible for implementing the semantics associated 118with the device. When a terminal file is first opened by a program, 119the default 120.Em line discipline 121called the 122.Dv termios 123line discipline is associated with the file. This is the primary 124line discipline that is used in most cases and provides the semantics 125that users normally associate with a terminal. When the 126.Dv termios 127line discipline is in effect, the terminal file behaves and is 128operated according to the rules described in 129.Xr termios 4 . 130Please refer to that man page for a full description of the terminal 131semantics. 132The operations described here 133generally represent features common 134across all 135.Em line disciplines , 136however some of these calls may not 137make sense in conjunction with a line discipline other than 138.Dv termios , 139and some may not be supported by the underlying 140hardware (or lack thereof, as in the case of ptys). 141.Ss Terminal File Operations 142All of the following operations are invoked using the 143.Xr ioctl 2 144system call. Refer to that man page for a description of 145the 146.Em request 147and 148.Em argp 149parameters. 150In addition to the ioctl 151.Em requests 152defined here, the specific line discipline 153in effect will define other 154.Em requests 155specific to it (actually 156.Xr termios 4 157defines them as function calls, not ioctl 158.Em requests . ) 159The following section lists the available ioctl requests. The 160name of the request, a description of its purpose, and the typed 161.Em argp 162parameter (if any) 163are listed. For example, the first entry says 164.Pp 165.D1 Em TIOCSLINED char name[32] 166.Pp 167and would be called on the terminal associated with 168file descriptor zero by the following code fragment: 169.Bd -literal 170 ioctl(0, TIOCSLINED, "termios"); 171.Ed 172.Ss Terminal File Request Descriptions 173.Bl -tag -width TIOCGWINSZ 174.It Dv TIOCSLINED Fa char name[32] 175Change to the new line discipline called 176.Fa name . 177.Pp 178.It Dv TIOCGLINED Fa char name[32] 179Return the current line discipline in the string pointed to by 180.Fa name . 181.It Dv TIOCSBRK Fa void 182Set the terminal hardware into BREAK condition. 183.It Dv TIOCCBRK Fa void 184Clear the terminal hardware BREAK condition. 185.It Dv TIOCSDTR Fa void 186Assert data terminal ready (DTR). 187.It Dv TIOCCDTR Fa void 188Clear data terminal ready (DTR). 189.It Dv TIOCGPGRP Fa int *tpgrp 190Return the current process group the terminal is associated 191with in the integer pointed to by 192.Fa tpgrp . 193This is the underlying call that implements the 194.Xr tcgetpgrp 3 195call. 196.It Dv TIOCSPGRP Fa int *tpgrp 197Associate the terminal with the process group (as an integer) pointed to by 198.Fa tpgrp . 199This is the underlying call that implements the 200.Xr tcsetpgrp 3 201call. 202.It Dv TIOCGETA Fa struct termios *term 203Place the current value of the termios state associated with the 204device in the termios structure pointed to by 205.Fa term . 206This is the underlying call that implements the 207.Xr tcgetattr 3 208call. 209.It Dv TIOCSETA Fa struct termios *term 210Set the termios state associated with the device immediately. 211This is the underlying call that implements the 212.Xr tcsetattr 3 213call with the 214.Dv TCSANOW 215option. 216.It Dv TIOCSETAW Fa struct termios *term 217First wait for any output to complete, then set the termios state 218associated with the device. 219This is the underlying call that implements the 220.Xr tcsetattr 3 221call with the 222.Dv TCSADRAIN 223option. 224.It Dv TIOCSETAF Fa struct termios *term 225First wait for any output to complete, clear any pending input, 226then set the termios state associated with the device. 227This is the underlying call that implements the 228.Xr tcsetattr 3 229call with the 230.Dv TCSAFLUSH 231option. 232.It Dv TIOCOUTQ Fa int *num 233Place the current number of characters in the output queue in the 234integer pointed to by 235.Fa num . 236.It Dv TIOCSTI Fa char *cp 237Simulate typed input. Pretend as if the terminal received the 238character pointed to by 239.Fa cp . 240.It Dv TIOCNOTTY Fa void 241This call is obsolete but left for compatibility. In the past, when 242a process that didn't have a controlling terminal (see 243.Em The Controlling Terminal 244in 245.Xr termios 4 ) 246first opened a terminal device, it acquired that terminal as its 247controlling terminal. For some programs this was a hazard as they 248didn't want a controlling terminal in the first place, and this 249provided a mechanism to disassociate the controlling terminal from 250the calling process. It 251.Em must 252be called by opening the file 253.Pa /dev/tty 254and calling 255.Dv TIOCNOTTY 256on that file descriptor. 257.Pp 258The current system does not allocate a controlling terminal to 259a process on an 260.Fn open 261call: there is a specific ioctl called 262.Dv TIOCSCTTY 263to make a terminal the controlling 264terminal. 265In addition, a program can 266.Fn fork 267and call the 268.Fn setsid 269system call which will place the process into its own session - which 270has the effect of disassociating it from the controlling terminal. This 271is the new and preferred method for programs to lose their controlling 272terminal. 273.It Dv TIOCSTOP Fa void 274Stop output on the terminal (like typing ^S at the keyboard). 275.It Dv TIOCSTART Fa void 276Start output on the terminal (like typing ^Q at the keyboard). 277.It Dv TIOCSCTTY Fa void 278Make the terminal the controlling terminal for the process (the process 279must not currently have a controlling terminal). 280.It Dv TIOCDRAIN Fa void 281Wait until all output is drained. 282.It Dv TIOCEXCL Fa void 283Set exclusive use on the terminal. No further opens are permitted 284except by root. Of course, this means that programs that are run by 285root (or setuid) will not obey the exclusive setting - which limits 286the usefulness of this feature. 287.It Dv TIOCNXCL Fa void 288Clear exclusive use of the terminal. Further opens are permitted. 289.It Dv TIOCFLUSH Fa int *what 290If the value of the int pointed to by 291.Fa what 292contains the 293.Dv FREAD 294bit as defined in 295.Aq Pa sys/fcntl.h , 296then all characters in the input queue are cleared. If it contains 297the 298.Dv FWRITE 299bit, then all characters in the output queue are cleared. If the 300value of the integer is zero, then it behaves as if both the 301.Dv FREAD 302and 303.Dv FWRITE 304bits were set (i.e. clears both queues). 305.It Dv TIOCGWINSZ Fa struct winsize *ws 306Put the window size information associated with the terminal in the 307.Va winsize 308structure pointed to by 309.Fa ws . 310The window size structure contains the number of rows and columns (and pixels 311if appropriate) of the devices attached to the terminal. It is set by user software 312and is the means by which most full\&-screen oriented programs determine the 313screen size. The 314.Va winsize 315structure is defined in 316.Aq Pa sys/ioctl.h . 317.It Dv TIOCSWINSZ Fa struct winsize *ws 318Set the window size associated with the terminal to be the value in 319the 320.Va winsize 321structure pointed to by 322.Fa ws 323(see above). 324.It Dv TIOCCONS Fa int *on 325If 326.Fa on 327points to a non-zero integer, redirect kernel console output (kernel printf's) 328to this terminal. 329If 330.Fa on 331points to a zero integer, redirect kernel console output back to the normal 332console. This is usually used on workstations to redirect kernel messages 333to a particular window. 334.It Dv TIOCMSET Fa int *state 335The integer pointed to by 336.Fa state 337contains bits that correspond to modem state. Following is a list 338of defined variables and the modem state they represent: 339.Pp 340.Bl -tag -width TIOCMXCTS -compact 341.It TIOCM_LE 342Line Enable. 343.It TIOCM_DTR 344Data Terminal Ready. 345.It TIOCM_RTS 346Request To Send. 347.It TIOCM_ST 348Secondary Transmit. 349.It TIOCM_SR 350Secondary Receive. 351.It TIOCM_CTS 352Clear To Send. 353.It TIOCM_CAR 354Carrier Detect. 355.It TIOCM_CD 356Carrier Detect (synonym). 357.It TIOCM_RNG 358Ring Indication. 359.It TIOCM_RI 360Ring Indication (synonym). 361.It TIOCM_DSR 362Data Set Ready. 363.El 364.Pp 365This call sets the terminal modem state to that represented by 366.Fa state . 367Not all terminals may support this. 368.It Dv TIOCMGET Fa int *state 369Return the current state of the terminal modem lines as represented 370above in the integer pointed to by 371.Fa state . 372.It Dv TIOCMBIS Fa int *state 373The bits in the integer pointed to by 374.Fa state 375represent modem state as described above, however the state is OR-ed 376in with the current state. 377.It Dv TIOCMBIC Fa int *state 378The bits in the integer pointed to by 379.Fa state 380represent modem state as described above, however each bit which is on 381in 382.Fa state 383is cleared in the terminal. 384.It Dv TIOCSFLAGS Fa int *state 385The bits in the integer pointed to by 386.Fa state 387contain bits that correspond to serial port state. Following is a list 388of defined variables and the serial port state they represent: 389.Pp 390.Bl -tag -width TIOCFLAG_SOFTCAR -compact 391.It TIOCFLAG_SOFTCAR 392Ignore hardware carrier. 393.It TIOCFLAG_CLOCAL 394Set clocal on open. 395.It TIOCFLAG_CRTSCTS 396Set crtscts on open. 397.It TIOCFLAG_MDMBUF 398Set mdmbuf on open. 399.El 400.Pp 401This call sets the serial port state to that represented by 402.Fa state . 403Not all serial ports may support this. 404.It Dv TIOCGFLAGS Fa int *state 405Return the current state of the serial port as represented 406above in the integer pointed to by 407.Fa state . 408.El 409.Sh COMPATIBILITY 410Two ioctls are maintained for backwards compatibility. They provide 411methods to get and set the current line discipline, but are not 412extensible. 413.Bl -tag -width TIOCGWINSZ 414.It Dv TIOCSETD Fa int *ldisc 415Change to the new line discipline pointed to by 416.Fa ldisc . 417The old list of available line disciplines are listed in 418.Aq Pa sys/ttycom.h 419and are: 420.Pp 421.Bl -tag -width TIOCGWINSZ -compact 422.It TTYDISC 423Termios interactive line discipline. 424.It TABLDISC 425Tablet line discipline. 426.It SLIPDISC 427Serial IP line discipline. 428.It PPPDISC 429Point to Point Protocol line discipline. 430.It STRIPDISC 431Starmode Radio IP line discipline. 432.El 433.Pp 434.It Dv TIOCGETD Fa int *ldisc 435Return the current line discipline in the integer pointed to by 436.Fa ldisc . 437.El 438.Sh SEE ALSO 439.Xr stty 1 , 440.Xr ioctl 2 , 441.Xr tcgetattr 3 , 442.Xr tcsetattr 3 , 443.Xr pty 4 , 444.Xr termios 4 , 445.Xr getty 8 , 446.Xr linedisc 9 447.Sh HISTORY 448Separate dial-out device files were implemented in SunOS 4. They were cloned 449by Charles M. Hannum for 450.Nx 1.4 . 451