1.\" $NetBSD: tty.4,v 1.5 1997/04/03 00:56:29 kleink 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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)tty.4 8.3 (Berkeley) 4/19/94 35.\" 36.Dd August 14, 1992 37.Dt TTY 4 38.Os BSD 4 39.Sh NAME 40.Nm tty 41.Nd general terminal interface 42.Sh SYNOPSIS 43.Fd #include <sys/ioctl.h> 44.Sh DESCRIPTION 45This section describes the interface to the terminal drivers 46in the system. 47.Ss Terminal Special Files 48Each hardware terminal port on the system usually has a terminal special device 49file associated with it in the directory ``/dev/'' (for 50example, ``/dev/tty03''). 51When a user logs into 52the system on one of these hardware terminal ports, the system has already 53opened the associated device and prepared the line for normal interactive 54use (see 55.Xr getty 8 .) 56There is also a special case of a terminal file that connects not to 57a hardware terminal port, but to another program on the other side. 58These special terminal devices are called 59.Em ptys 60and provide the mechanism necessary to give users the same interface to the 61system when logging in over a network (using 62.Xr rlogin 1 , 63or 64.Xr telnet 1 65for example.) Even in these cases the details of how the terminal 66file was opened and set up is already handled by special software 67in the system. 68Thus, users do not normally need to worry about the details of 69how these lines are opened or used. Also, these lines are often used 70for dialing out of a system (through an out-calling modem), but again 71the system provides programs that hide the details of accessing 72these terminal special files (see 73.Xr tip 2 .) 74.Pp 75When an interactive user logs in, the system prepares the line to 76behave in a certain way (called a 77.Em "line discipline" ) , 78the particular details of which is described in 79.Xr stty 1 80at the command level, and in 81.Xr termios 4 82at the programming level. A user may be concerned with changing 83settings associated with his particular login terminal and should refer 84to the preceding man pages for the common cases. The remainder of 85this man page is concerned 86with describing details of using and controlling terminal devices 87at a low level, such as that possibly required by a program wishing 88to provide features similar to those provided by the system. 89.Ss Line disciplines 90A terminal file is used like any other file in the system in that 91it can be opened, read, and written to using standard system 92calls. For each existing terminal file, there is a software processing module 93called a 94.Em "line discipline" 95is associated with it. The 96.Em "line discipline" 97essentially glues the low level device driver code with the high 98level generic interface routines (such as 99.Xr read 2 100and 101.Xr write 2 ), 102and is responsible for implementing the semantics associated 103with the device. When a terminal file is first opened by a program, 104the default 105.Em "line discipline" 106called the 107.Dv termios 108line discipline is associated with the file. This is the primary 109line discipline that is used in most cases and provides the semantics 110that users normally associate with a terminal. When the 111.Dv termios 112line discipline is in effect, the terminal file behaves and is 113operated according to the rules described in 114.Xr termios 4 . 115Please refer to that man page for a full description of the terminal 116semantics. 117The operations described here 118generally represent features common 119across all 120.Em "line disciplines" , 121however some of these calls may not 122make sense in conjunction with a line discipline other than 123.Dv termios , 124and some may not be supported by the underlying 125hardware (or lack thereof, as in the case of ptys). 126.Ss Terminal File Operations 127All of the following operations are invoked using the 128.Xr ioctl 2 129system call. Refer to that man page for a description of 130the 131.Em request 132and 133.Em argp 134parameters. 135In addition to the ioctl 136.Em requests 137defined here, the specific line discipline 138in effect will define other 139.Em requests 140specific to it (actually 141.Xr termios 4 142defines them as function calls, not ioctl 143.Em requests . ) 144The following section lists the available ioctl requests. The 145name of the request, a description of its purpose, and the typed 146.Em argp 147parameter (if any) 148are listed. For example, the first entry says 149.Pp 150.D1 Em "TIOCSETD int *ldisc" 151.Pp 152and would be called on the terminal associated with 153file descriptor zero by the following code fragment: 154.Bd -literal 155 int ldisc; 156 157 ldisc = TTYDISC; 158 ioctl(0, TIOCSETD, &ldisc); 159.Ed 160.Ss Terminal File Request Descriptions 161.Bl -tag -width TIOCGWINSZ 162.It Dv TIOCSETD Fa int *ldisc 163Change to the new line discipline pointed to by 164.Fa ldisc . 165The available line disciplines are listed in 166.Pa Aq sys/ttycom.h 167and currently are: 168.Pp 169.Bl -tag -width TIOCGWINSZ -compact 170.It TTYDISC 171Termios interactive line discipline. 172.It TABLDISC 173Tablet line discipline. 174.It SLIPDISC 175Serial IP line discipline. 176.It PPPDISC 177Point to Point Protocol line discipline. 178.It STRIPDISC 179Starmode Radio IP line discipline. 180.El 181.Pp 182.It Dv TIOCGETD Fa int *ldisc 183Return the current line discipline in the integer pointed to by 184.Fa ldisc . 185.It Dv TIOCSBRK Fa void 186Set the terminal hardware into BREAK condition. 187.It Dv TIOCCBRK Fa void 188Clear the terminal hardware BREAK condition. 189.It Dv TIOCSDTR Fa void 190Assert data terminal ready (DTR). 191.It Dv TIOCCDTR Fa void 192Clear data terminal ready (DTR). 193.It Dv TIOCGPGRP Fa int *tpgrp 194Return the current process group the terminal is associated 195with in the integer pointed to by 196.Fa tpgrp . 197This is the underlying call that implements the 198.Xr termios 4 199.Fn tcgetattr 200call. 201.It Dv TIOCSPGRP Fa int *tpgrp 202Associate the terminal with the process group (as an integer) pointed to by 203.Fa tpgrp . 204This is the underlying call that implements the 205.Xr termios 4 206.Fn tcsetattr 207call. 208.It Dv TIOCGETA Fa struct termios *term 209Place the current value of the termios state associated with the 210device in the termios structure pointed to by 211.Fa term . 212This is the underlying call that implements the 213.Xr termios 4 214.Fn tcgetattr 215call. 216.It Dv TIOCSETA Fa struct termios *term 217Set the termios state associated with the device immediately. 218This is the underlying call that implements the 219.Xr termios 4 220.Fn tcsetattr 221call with the 222.Dv TCSANOW 223option. 224.It Dv TIOCSETAW Fa struct termios *term 225First wait for any output to complete, then set the termios state 226associated with the device. 227This is the underlying call that implements the 228.Xr termios 4 229.Fn tcsetattr 230call with the 231.Dv TCSADRAIN 232option. 233.It Dv TIOCSETAF Fa struct termios *term 234First wait for any output to complete, clear any pending input, 235then set the termios state associated with the device. 236This is the underlying call that implements the 237.Xr termios 4 238.Fn tcsetattr 239call with the 240.Dv TCSAFLUSH 241option. 242.It Dv TIOCOUTQ Fa int *num 243Place the current number of characters in the output queue in the 244integer pointed to by 245.Fa num . 246.It Dv TIOCSTI Fa char *cp 247Simulate typed input. Pretend as if the terminal received the 248character pointed to by 249.Fa cp . 250.It Dv TIOCNOTTY Fa void 251This call is obsolete but left for compatibility. In the past, when 252a process that didn't have a controlling terminal (see 253.Em The Controlling Terminal 254in 255.Xr termios 4 ) 256first opened a terminal device, it acquired that terminal as its 257controlling terminal. For some programs this was a hazard as they 258didn't want a controlling terminal in the first place, and this 259provided a mechanism to disassociate the controlling terminal from 260the calling process. It 261.Em must 262be called by opening the file 263.Pa /dev/tty 264and calling 265.Dv TIOCNOTTY 266on that file descriptor. 267.Pp 268The current system does not allocate a controlling terminal to 269a process on an 270.Fn open 271call: there is a specific ioctl called 272.Dv TIOSCTTY 273to make a terminal the controlling 274terminal. 275In addition, a program can 276.Fn fork 277and call the 278.Fn setsid 279system call which will place the process into its own session - which 280has the effect of disassociating it from the controlling terminal. This 281is the new and preferred method for programs to lose their controlling 282terminal. 283.It Dv TIOCSTOP Fa void 284Stop output on the terminal (like typing ^S at the keyboard). 285.It Dv TIOCSTART Fa void 286Start output on the terminal (like typing ^Q at the keyboard). 287.It Dv TIOCSCTTY Fa void 288Make the terminal the controlling terminal for the process (the process 289must not currently have a controlling terminal). 290.It Dv TIOCDRAIN Fa void 291Wait until all output is drained. 292.It Dv TIOCEXCL Fa void 293Set exclusive use on the terminal. No further opens are permitted 294except by root. Of course, this means that programs that are run by 295root (or setuid) will not obey the exclusive setting - which limits 296the usefulness of this feature. 297.It Dv TIOCNXCL Fa void 298Clear exclusive use of the terminal. Further opens are permitted. 299.It Dv TIOCFLUSH Fa int *what 300If the value of the int pointed to by 301.Fa what 302contains the 303.Dv FREAD 304bit as defined in 305.Pa Aq sys/file.h , 306then all characters in the input queue are cleared. If it contains 307the 308.Dv FWRITE 309bit, then all characters in the output queue are cleared. If the 310value of the integer is zero, then it behaves as if both the 311.Dv FREAD 312and 313.Dv FWRITE 314bits were set (i.e. clears both queues). 315.It Dv TIOCGWINSZ Fa struct winsize *ws 316Put the window size information associated with the terminal in the 317.Va winsize 318structure pointed to by 319.Fa ws . 320The window size structure contains the number of rows and columns (and pixels 321if appropriate) of the devices attached to the terminal. It is set by user software 322and is the means by which most full\&-screen oriented programs determine the 323screen size. The 324.Va winsize 325structure is defined in 326.Pa Aq sys/ioctl.h . 327.It Dv TIOCSWINSZ Fa struct winsize *ws 328Set the window size associated with the terminal to be the value in 329the 330.Va winsize 331structure pointed to by 332.Fa ws 333(see above). 334.It Dv TIOCCONS Fa int *on 335If 336.Fa on 337points to a non-zero integer, redirect kernel console output (kernel printf's) 338to this terminal. 339If 340.Fa on 341points to a zero integer, redirect kernel console output back to the normal 342console. This is usually used on workstations to redirect kernel messages 343to a particular window. 344.It Dv TIOCMSET Fa int *state 345The integer pointed to by 346.Fa state 347contains bits that correspond to modem state. Following is a list 348of defined variables and the modem state they represent: 349.Pp 350.Bl -tag -width TIOCMXCTS -compact 351.It TIOCM_LE 352Line Enable. 353.It TIOCM_DTR 354Data Terminal Ready. 355.It TIOCM_RTS 356Request To Send. 357.It TIOCM_ST 358Secondary Transmit. 359.It TIOCM_SR 360Secondary Receive. 361.It TIOCM_CTS 362Clear To Send. 363.It TIOCM_CAR 364Carrier Detect. 365.It TIOCM_CD 366Carier Detect (synonym). 367.It TIOCM_RNG 368Ring Indication. 369.It TIOCM_RI 370Ring Indication (synonym). 371.It TIOCM_DSR 372Data Set Ready. 373.El 374.Pp 375This call sets the terminal modem state to that represented by 376.Fa state . 377Not all terminals may support this. 378.It Dv TIOCMGET Fa int *state 379Return the current state of the terminal modem lines as represented 380above in the integer pointed to by 381.Fa state . 382.It Dv TIOCMBIS Fa int *state 383The bits in the integer pointed to by 384.Fa state 385represent modem state as described above, however the state is OR-ed 386in with the current state. 387.It Dv TIOCMBIC Fa int *state 388The bits in the integer pointed to by 389.Fa state 390represent modem state as described above, however each bit which is on 391in 392.Fa state 393is cleared in the terminal. 394.It Dv TIOCSFLAGS Fa int *state 395The bits in the integer pointed to by 396.Fa state 397contain bits that correspond to serial port state. Following is a list 398of defined variables and the serial port state they represent: 399.Pp 400.Bl -tag -width TIOCFLAG_SOFTCAR -compact 401.It TIOCFLAG_SOFTCAR 402Ignore hardware carrier. 403.It TIOCFLAG_CLOCAL 404Set clocal on open. 405.It TIOCFLAG_CRTSCTS 406Set crtscts on open. 407.It TIOCFLAG_MDMBUF 408Set mdmbuf on open. 409.El 410.Pp 411This call sets the serial port state to that represented by 412.Fa state . 413Not all serial ports may support this. 414.It Dv TIOCGFLAGS Fa int *state 415Return the current state of the serial port as represented 416above in the integer pointed to by 417.Fa state . 418.El 419.Sh SEE ALSO 420.Xr getty 8 , 421.Xr ioctl 2 , 422.Xr pty 4 , 423.Xr stty 1 , 424.Xr termios 4 425