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 38.Sh NAME 39.Nm tty 40.Nd general terminal interface 41.Sh SYNOPSIS 42.In 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.Aq Pa sys/ttycom.h 166and currently are: 167.Pp 168.Bl -tag -width NETGRAPHDISC -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.It NETGRAPHDISC 178Netgraph 179.Xr ng_tty 4 180line discipline. 181.El 182.Pp 183.It Dv TIOCGETD Fa int *ldisc 184Return the current line discipline in the integer pointed to by 185.Fa ldisc . 186.It Dv TIOCSBRK Fa void 187Set the terminal hardware into BREAK condition. 188.It Dv TIOCCBRK Fa void 189Clear the terminal hardware BREAK condition. 190.It Dv TIOCSDTR Fa void 191Assert data terminal ready (DTR). 192.It Dv TIOCCDTR Fa void 193Clear data terminal ready (DTR). 194.It Dv TIOCGPGRP Fa int *tpgrp 195Return the current process group with which the terminal is associated 196in the integer pointed to by 197.Fa tpgrp . 198This is the underlying call that implements the 199.Xr termios 4 200.Fn tcgetattr 201call. 202.It Dv TIOCSPGRP Fa int *tpgrp 203Associate the terminal with the process group (as an integer) pointed to by 204.Fa tpgrp . 205This is the underlying call that implements the 206.Xr termios 4 207.Fn tcsetattr 208call. 209.It Dv TIOCGETA Fa struct termios *term 210Place the current value of the termios state associated with the 211device in the termios structure pointed to by 212.Fa term . 213This is the underlying call that implements the 214.Xr termios 4 215.Fn tcgetattr 216call. 217.It Dv TIOCSETA Fa struct termios *term 218Set the termios state associated with the device immediately. 219This is the underlying call that implements the 220.Xr termios 4 221.Fn tcsetattr 222call with the 223.Dv TCSANOW 224option. 225.It Dv TIOCSETAW Fa struct termios *term 226First wait for any output to complete, then set the termios state 227associated with the device. 228This is the underlying call that implements the 229.Xr termios 4 230.Fn tcsetattr 231call with the 232.Dv TCSADRAIN 233option. 234.It Dv TIOCSETAF Fa struct termios *term 235First wait for any output to complete, clear any pending input, 236then set the termios state associated with the device. 237This is the underlying call that implements the 238.Xr termios 4 239.Fn tcsetattr 240call with the 241.Dv TCSAFLUSH 242option. 243.It Dv TIOCOUTQ Fa int *num 244Place the current number of characters in the output queue in the 245integer pointed to by 246.Fa num . 247.It Dv TIOCSTI Fa char *cp 248Simulate typed input. Pretend as if the terminal received the 249character pointed to by 250.Fa cp . 251.It Dv TIOCNOTTY Fa void 252This call is obsolete but left for compatibility. In the past, when 253a process that didn't have a controlling terminal (see 254.Em The Controlling Terminal 255in 256.Xr termios 4 ) 257first opened a terminal device, it acquired that terminal as its 258controlling terminal. For some programs this was a hazard as they 259didn't want a controlling terminal in the first place, and this 260provided a mechanism to disassociate the controlling terminal from 261the calling process. It 262.Em must 263be called by opening the file 264.Pa /dev/tty 265and calling 266.Dv TIOCNOTTY 267on that file descriptor. 268.Pp 269The current system does not allocate a controlling terminal to 270a process on an 271.Fn open 272call: there is a specific ioctl called 273.Dv TIOSCTTY 274to make a terminal the controlling 275terminal. 276In addition, a program can 277.Fn fork 278and call the 279.Fn setsid 280system call which will place the process into its own session - which 281has the effect of disassociating it from the controlling terminal. This 282is the new and preferred method for programs to lose their controlling 283terminal. 284.It Dv TIOCSTOP Fa void 285Stop output on the terminal (like typing ^S at the keyboard). 286.It Dv TIOCSTART Fa void 287Start output on the terminal (like typing ^Q at the keyboard). 288.It Dv TIOCSCTTY Fa void 289Make the terminal the controlling terminal for the process (the process 290must not currently have a controlling terminal). 291.It Dv TIOCDRAIN Fa void 292Wait until all output is drained. 293.It Dv TIOCEXCL Fa void 294Set exclusive use on the terminal. No further opens are permitted 295except by root. Of course, this means that programs that are run by 296root (or setuid) will not obey the exclusive setting - which limits 297the usefulness of this feature. 298.It Dv TIOCNXCL Fa void 299Clear exclusive use of the terminal. Further opens are permitted. 300.It Dv TIOCFLUSH Fa int *what 301If the value of the int pointed to by 302.Fa what 303contains the 304.Dv FREAD 305bit as defined in 306.Aq Pa sys/file.h , 307then all characters in the input queue are cleared. If it contains 308the 309.Dv FWRITE 310bit, then all characters in the output queue are cleared. If the 311value of the integer is zero, then it behaves as if both the 312.Dv FREAD 313and 314.Dv FWRITE 315bits were set (i.e. clears both queues). 316.It Dv TIOCGWINSZ Fa struct winsize *ws 317Put the window size information associated with the terminal in the 318.Va winsize 319structure pointed to by 320.Fa ws . 321The window size structure contains the number of rows and columns (and pixels 322if appropriate) of the devices attached to the terminal. It is set by user software 323and is the means by which most full\&-screen oriented programs determine the 324screen size. The 325.Va winsize 326structure is defined in 327.Aq Pa sys/ioctl.h . 328.It Dv TIOCSWINSZ Fa struct winsize *ws 329Set the window size associated with the terminal to be the value in 330the 331.Va winsize 332structure pointed to by 333.Fa ws 334(see above). 335.It Dv TIOCCONS Fa int *on 336If 337.Fa on 338points to a non-zero integer, redirect kernel console output (kernel printf's) 339to this terminal. 340If 341.Fa on 342points to a zero integer, redirect kernel console output back to the normal 343console. This is usually used on workstations to redirect kernel messages 344to a particular window. 345.It Dv TIOCMSET Fa int *state 346The integer pointed to by 347.Fa state 348contains bits that correspond to modem state. Following is a list 349of defined variables and the modem state they represent: 350.Pp 351.Bl -tag -width TIOCMXCTS -compact 352.It TIOCM_LE 353Line Enable. 354.It TIOCM_DTR 355Data Terminal Ready. 356.It TIOCM_RTS 357Request To Send. 358.It TIOCM_ST 359Secondary Transmit. 360.It TIOCM_SR 361Secondary Receive. 362.It TIOCM_CTS 363Clear To Send. 364.It TIOCM_CAR 365Carrier Detect. 366.It TIOCM_CD 367Carrier Detect (synonym). 368.It TIOCM_RNG 369Ring Indication. 370.It TIOCM_RI 371Ring Indication (synonym). 372.It TIOCM_DSR 373Data Set Ready. 374.El 375.Pp 376This call sets the terminal modem state to that represented by 377.Fa state . 378Not all terminals may support this. 379.It Dv TIOCMGET Fa int *state 380Return the current state of the terminal modem lines as represented 381above in the integer pointed to by 382.Fa state . 383.It Dv TIOCMBIS Fa int *state 384The bits in the integer pointed to by 385.Fa state 386represent modem state as described above, however the state is OR-ed 387in with the current state. 388.It Dv TIOCMBIC Fa int *state 389The bits in the integer pointed to by 390.Fa state 391represent modem state as described above, however each bit which is on 392in 393.Fa state 394is cleared in the terminal. 395.El 396.Sh IMPLEMENTATION NOTES 397The total number of input and output bytes 398through all terminal devices 399are available via the 400.Va kern.tk_nin 401and 402.Va kern.tk_nout 403read-only 404.Xr sysctl 8 405variables. 406.Sh SEE ALSO 407.Xr stty 1 , 408.Xr ioctl 2 , 409.Xr ng_tty 4 , 410.Xr pty 4 , 411.Xr termios 4 , 412.Xr getty 8 413