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 44This section describes the interface to the terminal drivers 45in the system. 46.Ss Terminal Special Files 47Each hardware terminal port on the system usually has a terminal special device 48file associated with it in the directory ``/dev/'' (for 49example, ``/dev/tty03''). 50When a user logs into 51the system on one of these hardware terminal ports, the system has already 52opened the associated device and prepared the line for normal interactive 53use (see 54.Xr getty 8 .) 55There is also a special case of a terminal file that connects not to 56a hardware terminal port, but to another program on the other side. 57These special terminal devices are called 58.Em ptys 59and provide the mechanism necessary to give users the same interface to the 60system when logging in over a network (using 61.Xr rlogin 1 , 62or 63.Xr telnet 1 64for example). Even in these cases the details of how the terminal 65file was opened and set up is already handled by special software 66in the system. 67Thus, users do not normally need to worry about the details of 68how these lines are opened or used. Also, these lines are often used 69for dialing out of a system (through an out-calling modem), but again 70the system provides programs that hide the details of accessing 71these terminal special files (see 72.Xr tip 1 ). 73.Pp 74When an interactive user logs in, the system prepares the line to 75behave in a certain way (called a 76.Em "line discipline" ) , 77the particular details of which is described in 78.Xr stty 1 79at the command level, and in 80.Xr termios 4 81at the programming level. A user may be concerned with changing 82settings associated with his particular login terminal and should refer 83to the preceding man pages for the common cases. The remainder of 84this man page is concerned 85with describing details of using and controlling terminal devices 86at a low level, such as that possibly required by a program wishing 87to provide features similar to those provided by the system. 88.Ss Line disciplines 89A terminal file is used like any other file in the system in that 90it can be opened, read, and written to using standard system 91calls. For each existing terminal file, there is a software processing module 92called a 93.Em "line discipline" 94is associated with it. The 95.Em "line discipline" 96essentially glues the low level device driver code with the high 97level generic interface routines (such as 98.Xr read 2 99and 100.Xr write 2 ), 101and is responsible for implementing the semantics associated 102with the device. When a terminal file is first opened by a program, 103the default 104.Em "line discipline" 105called the 106.Dv termios 107line discipline is associated with the file. This is the primary 108line discipline that is used in most cases and provides the semantics 109that users normally associate with a terminal. When the 110.Dv termios 111line discipline is in effect, the terminal file behaves and is 112operated according to the rules described in 113.Xr termios 4 . 114Please refer to that man page for a full description of the terminal 115semantics. 116The operations described here 117generally represent features common 118across all 119.Em "line disciplines" , 120however some of these calls may not 121make sense in conjunction with a line discipline other than 122.Dv termios , 123and some may not be supported by the underlying 124hardware (or lack thereof, as in the case of ptys). 125.Ss Terminal File Operations 126All of the following operations are invoked using the 127.Xr ioctl 2 128system call. Refer to that man page for a description of 129the 130.Em request 131and 132.Em argp 133parameters. 134In addition to the ioctl 135.Em requests 136defined here, the specific line discipline 137in effect will define other 138.Em requests 139specific to it (actually 140.Xr termios 4 141defines them as function calls, not ioctl 142.Em requests . ) 143The following section lists the available ioctl requests. The 144name of the request, a description of its purpose, and the typed 145.Em argp 146parameter (if any) 147are listed. For example, the first entry says 148.Pp 149.D1 Em "TIOCSETD int *ldisc" 150.Pp 151and would be called on the terminal associated with 152file 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 162Change to the new line discipline pointed to by 163.Fa ldisc . 164The available line disciplines are listed in 165.Pa Aq sys/ttycom.h 166and currently are: 167.Pp 168.Bl -tag -width TIOCGWINSZ -compact 169.It TTYDISC 170Termios interactive line discipline. 171.It TABLDISC 172Tablet line discipline. 173.It SLIPDISC 174Serial IP line discipline. 175.It PPPDISC 176PPP line discipline. 177.El 178.Pp 179.It Dv TIOCGETD Fa int *ldisc 180Return the current line discipline in the integer pointed to by 181.Fa ldisc . 182.It Dv TIOCSBRK Fa void 183Set the terminal hardware into BREAK condition. 184.It Dv TIOCCBRK Fa void 185Clear the terminal hardware BREAK condition. 186.It Dv TIOCSDTR Fa void 187Assert data terminal ready (DTR). 188.It Dv TIOCCDTR Fa void 189Clear data terminal ready (DTR). 190.It Dv TIOCGPGRP Fa int *tpgrp 191Return the current process group the terminal is associated 192with in the integer pointed to by 193.Fa tpgrp . 194This is the underlying call that implements the 195.Xr termios 4 196.Fn tcgetattr 197call. 198.It Dv TIOCSPGRP Fa int *tpgrp 199Associate the terminal with the process group (as an integer) pointed to by 200.Fa tpgrp . 201This is the underlying call that implements the 202.Xr termios 4 203.Fn tcsetattr 204call. 205.It Dv TIOCGETA Fa struct termios *term 206Place the current value of the termios state associated with the 207device in the termios structure pointed to by 208.Fa term . 209This is the underlying call that implements the 210.Xr termios 4 211.Fn tcgetattr 212call. 213.It Dv TIOCSETA Fa struct termios *term 214Set the termios state associated with the device immediately. 215This is the underlying call that implements the 216.Xr termios 4 217.Fn tcsetattr 218call with the 219.Dv TCSANOW 220option. 221.It Dv TIOCSETAW Fa struct termios *term 222First wait for any output to complete, then set the termios state 223associated with the device. 224This is the underlying call that implements the 225.Xr termios 4 226.Fn tcsetattr 227call with the 228.Dv TCSADRAIN 229option. 230.It Dv TIOCSETAF Fa struct termios *term 231First wait for any output to complete, clear any pending input, 232then set the termios state associated with the device. 233This is the underlying call that implements the 234.Xr termios 4 235.Fn tcsetattr 236call with the 237.Dv TCSAFLUSH 238option. 239.It Dv TIOCOUTQ Fa int *num 240Place the current number of characters in the output queue in the 241integer pointed to by 242.Fa num . 243.It Dv TIOCSTI Fa char *cp 244Simulate typed input. Pretend as if the terminal received the 245character pointed to by 246.Fa cp . 247.It Dv TIOCNOTTY Fa void 248This call is obsolete but left for compatibility. In the past, when 249a process that didn't have a controlling terminal (see 250.Em The Controlling Terminal 251in 252.Xr termios 4 ) 253first opened a terminal device, it acquired that terminal as its 254controlling terminal. For some programs this was a hazard as they 255didn't want a controlling terminal in the first place, and this 256provided a mechanism to disassociate the controlling terminal from 257the calling process. It 258.Em must 259be called by opening the file 260.Pa /dev/tty 261and calling 262.Dv TIOCNOTTY 263on that file descriptor. 264.Pp 265The current system does not allocate a controlling terminal to 266a process on an 267.Fn open 268call: there is a specific ioctl called 269.Dv TIOSCTTY 270to make a terminal the controlling 271terminal. 272In addition, a program can 273.Fn fork 274and call the 275.Fn setsid 276system call which will place the process into its own session - which 277has the effect of disassociating it from the controlling terminal. This 278is the new and preferred method for programs to lose their controlling 279terminal. 280.It Dv TIOCSTOP Fa void 281Stop output on the terminal (like typing ^S at the keyboard). 282.It Dv TIOCSTART Fa void 283Start output on the terminal (like typing ^Q at the keyboard). 284.It Dv TIOCSCTTY Fa void 285Make the terminal the controlling terminal for the process (the process 286must not currently have a controlling terminal). 287.It Dv TIOCDRAIN Fa void 288Wait until all output is drained. 289.It Dv TIOCEXCL Fa void 290Set exclusive use on the terminal. No further opens are permitted 291except by root. Of course, this means that programs that are run by 292root (or setuid) will not obey the exclusive setting - which limits 293the usefulness of this feature. 294.It Dv TIOCNXCL Fa void 295Clear exclusive use of the terminal. Further opens are permitted. 296.It Dv TIOCFLUSH Fa int *what 297If the value of the int pointed to by 298.Fa what 299contains the 300.Dv FREAD 301bit as defined in 302.Pa Aq sys/file.h , 303then all characters in the input queue are cleared. If it contains 304the 305.Dv FWRITE 306bit, then all characters in the output queue are cleared. If the 307value of the integer is zero, then it behaves as if both the 308.Dv FREAD 309and 310.Dv FWRITE 311bits were set (i.e. clears both queues). 312.It Dv TIOCGWINSZ Fa struct winsize *ws 313Put the window size information associated with the terminal in the 314.Va winsize 315structure pointed to by 316.Fa ws . 317The window size structure contains the number of rows and columns (and pixels 318if appropriate) of the devices attached to the terminal. It is set by user software 319and is the means by which most full\&-screen oriented programs determine the 320screen size. The 321.Va winsize 322structure is defined in 323.Pa Aq sys/ioctl.h . 324.It Dv TIOCSWINSZ Fa struct winsize *ws 325Set the window size associated with the terminal to be the value in 326the 327.Va winsize 328structure pointed to by 329.Fa ws 330(see above). 331.It Dv TIOCCONS Fa int *on 332If 333.Fa on 334points to a non-zero integer, redirect kernel console output (kernel printf's) 335to this terminal. 336If 337.Fa on 338points to a zero integer, redirect kernel console output back to the normal 339console. This is usually used on workstations to redirect kernel messages 340to a particular window. 341.It Dv TIOCMSET Fa int *state 342The integer pointed to by 343.Fa state 344contains bits that correspond to modem state. Following is a list 345of defined variables and the modem state they represent: 346.Pp 347.Bl -tag -width TIOCMXCTS -compact 348.It TIOCM_LE 349Line Enable. 350.It TIOCM_DTR 351Data Terminal Ready. 352.It TIOCM_RTS 353Request To Send. 354.It TIOCM_ST 355Secondary Transmit. 356.It TIOCM_SR 357Secondary Receive. 358.It TIOCM_CTS 359Clear To Send. 360.It TIOCM_CAR 361Carrier Detect. 362.It TIOCM_CD 363Carrier Detect (synonym). 364.It TIOCM_RNG 365Ring Indication. 366.It TIOCM_RI 367Ring Indication (synonym). 368.It TIOCM_DSR 369Data Set Ready. 370.El 371.Pp 372This call sets the terminal modem state to that represented by 373.Fa state . 374Not all terminals may support this. 375.It Dv TIOCMGET Fa int *state 376Return the current state of the terminal modem lines as represented 377above in the integer pointed to by 378.Fa state . 379.It Dv TIOCMBIS Fa int *state 380The bits in the integer pointed to by 381.Fa state 382represent modem state as described above, however the state is OR-ed 383in with the current state. 384.It Dv TIOCMBIC Fa int *state 385The bits in the integer pointed to by 386.Fa state 387represent modem state as described above, however each bit which is on 388in 389.Fa state 390is 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 8 398