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