1 .\" Copyright (c) 1991, 1992, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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.
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
32 .\" @(#)termios.4 8.4 (Berkeley) 4/19/94
40 .Nd general terminal line discipline
44 This describes a general terminal line discipline that is
45 supported on tty asynchronous communication ports.
46 .Ss Opening a Terminal Device File
47 When a terminal file is opened, it normally causes the process to wait
48 until a connection is established.
49 For most hardware, the presence
50 of a connection is indicated by the assertion of the hardware
53 If the termios structure associated with the terminal file has the
55 flag set in the cflag, or if the
60 call, then the open will succeed even without
61 a connection being present.
62 In practice, applications
63 seldom open these files; they are opened by special programs, such
69 an application's standard input, output, and error files.
70 .Ss Job Control in a Nutshell
71 Every process is associated with a particular process group and session.
72 The grouping is hierarchical: every member of a particular process group is a
73 member of the same session.
74 This structuring is used in managing groups
75 of related processes for purposes of
76 .\" .Gw "job control" ;
79 ability from the keyboard (or from program control) to simultaneously
81 a complex command (a command composed of one or more related
83 The grouping into process groups allows delivering
84 of signals that stop or start the group as a whole, along with
85 arbitrating which process group has access to the single controlling
87 The grouping at a higher layer into sessions is to restrict
88 the job control related signals and system calls to within processes
89 resulting from a particular instance of a
92 is created when a user logs in, and the login terminal is setup
93 to be the controlling terminal; all processes spawned from that
94 login shell are in the same session, and inherit the controlling
98 operating interactively (that is, reading commands from a terminal)
99 normally groups related processes together by placing them into the
101 A set of processes in the same process group
102 is collectively referred to as a
104 When the foreground process
105 group of the terminal is the same as the process group of a particular
106 job, that job is said to be in the
108 When the process group of the terminal is different from the process group of
109 a job (but is still the controlling terminal), that job is said
113 shell reads a command and starts the job that implements that
115 If the command is to be started in the foreground (typical), it
116 sets the process group of the terminal to the process group
117 of the started job, waits for the job to complete, and then
118 sets the process group of the terminal back to its own process
119 group (it puts itself into the foreground).
121 be started in the background (as denoted by the shell operator "&"),
122 it never changes the process group of the terminal and does not
123 wait for the job to complete (that is, it immediately attempts to read the next
125 If the job is started in the foreground, the user may
128 which generates the terminal stop signal
130 and has the effect of stopping the entire job.
131 The shell will notice that the job stopped, and will resume running after
132 placing itself in the foreground.
133 The shell also has commands for placing stopped jobs in the background,
134 and for placing stopped or background jobs into the foreground.
135 .Ss Orphaned Process Groups
136 An orphaned process group is a process group that has no process
137 whose parent is in a different process group, yet is in the same
139 Conceptually it means a process group that does not have
140 a parent that could do anything if it were to be stopped.
142 the initial login shell is typically in an orphaned process group.
143 Orphaned process groups are immune to keyboard generated stop
144 signals and job control signals resulting from reads or writes to the
145 controlling terminal.
146 .Ss The Controlling Terminal
147 A terminal may belong to a process as its controlling terminal.
149 process of a session that has a controlling terminal has the same
150 controlling terminal.
151 A terminal may be the controlling terminal for at
153 The controlling terminal for a session is allocated by
154 the session leader by issuing the
157 A controlling terminal
158 is never acquired by merely opening a terminal device file.
159 When a controlling terminal becomes
160 associated with a session, its foreground process group is set to
161 the process group of the session leader.
163 The controlling terminal is inherited by a child process during a
166 A process relinquishes its controlling terminal when it
167 creates a new session with the
169 function; other processes
170 remaining in the old session that had this terminal as their controlling
171 terminal continue to have it.
172 A process does not relinquish its
173 controlling terminal simply by closing all of its file descriptors
174 associated with the controlling terminal if other processes continue to
177 When a controlling process terminates, the controlling terminal is
178 disassociated from the current session, allowing it to be acquired by a
180 Subsequent access to the terminal by other processes
181 in the earlier session will be denied, with attempts to access the
182 terminal treated as if modem disconnect had been sensed.
183 .Ss Terminal Access Control
184 If a process is in the foreground process group of its controlling
185 terminal, read operations are allowed.
186 Any attempts by a process
187 in a background process group to read from its controlling terminal
193 following special cases apply: if the reading process is ignoring or
196 signal, or if the process group of the reading
197 process is orphaned, the
204 The default action of the
206 signal is to stop the
207 process to which it is sent.
209 If a process is in the foreground process group of its controlling
210 terminal, write operations are allowed.
211 Attempts by a process in a background process group to write to its
212 controlling terminal will cause the process group to be sent a
214 signal unless one of the following special cases apply: if
219 is set and the process is ignoring or blocking the
221 signal, the process is allowed to write to the terminal and the
226 is set, and the process group of
227 the writing process is orphaned, and the writing process is not ignoring
235 and no signal is sent.
237 Certain calls that set terminal parameters are treated in the same
238 fashion as write, except that
240 is ignored; that is, the effect is
241 identical to that of terminal writes when
244 .Ss Input Processing and Reading Data
245 A terminal device associated with a terminal device file may operate in
246 full-duplex mode, so that data may arrive even while output is occurring.
247 Each terminal device file has associated with it an input queue, into
248 which incoming data is stored by the system before being read by a
250 The system imposes a limit,
251 .Pf \&{ Dv MAX_INPUT Ns \&} ,
253 bytes that may be stored in the input queue.
254 The behavior of the system
255 when this limit is exceeded depends on the setting of the
259 If this flag is set, the terminal
263 character each time a character is received
264 while the input queue is full.
265 Otherwise, the input queue is flushed upon receiving the character.
267 Two general kinds of input processing are available, determined by
268 whether the terminal device file is in canonical mode or noncanonical
271 input characters are processed according to the
276 Such processing can include echoing, which
277 in general means transmitting input characters immediately back to the
278 terminal when they are received from the terminal.
279 This is useful for terminals that can operate in full-duplex mode.
281 The manner in which data is provided to a process reading from a terminal
282 device file is dependent on whether the terminal device file is in
283 canonical or noncanonical mode.
285 Another dependency is whether the
293 flag is clear, then the read request is
294 blocked until data is available or a signal has been received.
297 flag is set, then the read request is completed, without
298 blocking, in one of three ways:
299 .Bl -enum -offset indent
301 If there is enough data available to satisfy the entire request,
302 and the read completes successfully the number of
303 bytes read is returned.
305 If there is not enough data available to satisfy the entire
306 request, and the read completes successfully, having read as
307 much data as possible, the number of bytes read is returned.
309 If there is no data available, the read returns -1, with
314 When data is available depends on whether the input processing mode is
315 canonical or noncanonical.
316 .Ss Canonical Mode Input Processing
317 In canonical mode input processing, terminal input is processed in units
319 A line is delimited by a newline
321 character, an end-of-file
323 character, or an end-of-line
327 .Sx "Special Characters"
333 This means that a read request will
334 not return until an entire line has been typed, or a signal has been
336 Also, no matter how many bytes are requested in the read call,
337 at most one line is returned.
338 It is not, however, necessary to
339 read a whole line at once; any number of bytes, even one, may be
340 requested in a read without losing information.
342 .Pf \&{ Dv MAX_CANON Ns \&}
344 number of bytes in a line.
345 The behavior of the system when this limit is
346 exceeded is the same as when the input queue limit
347 .Pf \&{ Dv MAX_INPUT Ns \&} ,
350 Erase and kill processing occur when either of two special characters,
356 .Sx "Special Characters"
357 section), is received.
358 This processing affects data in the input queue that has not yet been
359 delimited by a newline
366 data makes up the current line.
369 character deletes the last
370 character in the current line, if there is any.
374 deletes all data in the current line, if there is any.
379 characters have no effect if there is no data in the current line.
384 characters themselves are not placed in the input
386 .Ss Noncanonical Mode Input Processing
387 In noncanonical mode input processing, input bytes are not assembled into
388 lines, and erase and kill processing does not occur.
395 array are used to determine how to
396 process the bytes received.
399 represents the minimum number of bytes that should be received when
402 function successfully returns.
404 is a timer of 0.1 second
405 granularity that is used to time out bursty and short term data
410 .Dv \&{ Dv MAX_INPUT Ns \&} ,
412 request is undefined.
413 The four possible values for
418 their interactions are described below.
419 .Ss "Case A: MIN > 0, TIME > 0"
422 serves as an inter-byte timer and is activated after
423 the first byte is received.
424 Since it is an inter-byte timer, it is reset
425 after a byte is received.
426 The interaction between
431 follows: as soon as one byte is received, the inter-byte timer is
435 bytes are received before the inter-byte timer expires
436 (remember that the timer is reset upon receipt of each byte), the read is
438 If the timer expires before
440 bytes are received, the
441 characters received to that point are returned to the user.
444 expires at least one byte is returned because the timer would
445 not have been enabled unless a byte was received.
450 > 0) the read blocks until the
455 activated by the receipt of the first byte, or a signal is received.
456 If data is in the buffer at the time of the
459 if data had been received immediately after the
461 .Ss "Case B: MIN > 0, TIME = 0"
462 In this case, since the value of
464 is zero, the timer plays no role
468 A pending read is not satisfied until
470 bytes are received (i.e., the pending read blocks until
473 are received), or a signal is received.
474 A program that uses this case to read record-based terminal
476 may block indefinitely in the read
478 .Ss "Case C: MIN = 0, TIME > 0"
483 no longer represents an inter-byte
485 It now serves as a read timer that is activated as soon as the
486 read function is processed.
487 A read is satisfied as soon as a single
488 byte is received or the read timer expires.
489 Note that in this case if the timer expires, no bytes are returned.
490 If the timer does not
491 expire, the only way the read can be satisfied is if a byte is received.
492 In this case the read will not block indefinitely waiting for a byte; if
493 no byte is received within
495 seconds after the read is initiated,
496 the read returns a value of zero, having read no data.
498 in the buffer at the time of the read, the timer is started as if
499 data had been received immediately after the read.
500 .Ss Case D: MIN = 0, TIME = 0
501 The minimum of either the number of bytes requested or the number of
502 bytes currently available is returned without waiting for more
504 If no characters are available, read returns a
505 value of zero, having read no data.
506 .Ss Writing Data and Output Processing
507 When a process writes one or more bytes to a terminal device file, they
508 are processed according to the
514 implementation may provide a buffering mechanism; as such, when a call to
516 completes, all of the bytes written have been scheduled for
517 transmission to the device, but the transmission will not necessarily
519 .\" See also .Sx "6.4.2" for the effects of
522 .Ss Special Characters
523 Certain characters have special functions on input or output or both.
524 These functions are summarized as follows:
525 .Bl -tag -width indent
527 Special character on input and is recognized if the
534 signal which is sent to all processes in the foreground
535 process group for which the terminal is the controlling
542 discarded when processed.
544 Special character on input and is recognized if the
550 sent to all processes in the foreground process group
551 for which the terminal is the controlling terminal.
556 character is discarded when
559 Special character on input and is recognized if the
562 Erases the last character in the
564 .Sx "Canonical Mode Input Processing" .
565 It does not erase beyond
566 the start of a line, as delimited by an
577 discarded when processed.
579 Special character on input and is recognized if the
582 Deletes the entire line, as
593 character is discarded when processed.
595 Special character on input and is recognized if the
598 When received, all the bytes
599 waiting to be read are immediately passed to the
600 process, without waiting for a newline, and the
603 Thus, if there are no bytes waiting (that is, the
605 occurred at the beginning of a line), a byte
606 count of zero is returned from the
608 representing an end-of-file indication.
614 character is discarded when processed.
616 Special character on input and is recognized if the
619 It is the line delimiter
622 Special character on input and is recognized if the
625 Is an additional line delimiter, like
630 flag is enabled, receipt of the
634 signal to be sent to all processes in the
635 foreground process group for which the terminal is the
636 controlling terminal, and the
639 discarded when processed.
641 Special character on both input and output and is
647 control) flag is set.
648 Can be used to temporarily suspend output.
649 It is useful with fast terminals to
650 prevent output from disappearing before it can be read.
655 character is discarded when
658 Special character on both input and output and is
664 control) flag is set.
665 Can be used to resume output that has been suspended by a
672 character is discarded when processed.
674 Special character on input and is recognized if the
676 flag is set; it is the
687 is not set, this character is translated into a
690 has the same effect as a
695 The following special characters are extensions defined by this
696 system and are not a part of
699 .Bl -tag -width indent
707 Special character on input and is recognized if the
710 Erases the last word in the current line according to one of two algorithms.
713 flag is not set, first any preceding whitespace is
714 erased, and then the maximal sequence of non-whitespace
718 is set, first any preceding
719 whitespace is erased, and then the maximal sequence
720 of alphabetic/underscores or non alphabetic/underscores.
721 As a special case in this second algorithm, the first previous
722 non-whitespace character is skipped in determining
723 whether the preceding word is a sequence of
724 alphabetic/underscores.
725 This sounds confusing but turns out to be quite practical.
727 Special character on input and is recognized if the
730 Causes the current input edit line to be retyped.
732 Has similar actions to the
734 character, except that
737 signal is delivered when one of the processes
738 in the foreground process group issues a
741 controlling terminal.
743 Special character on input and is recognized if the
746 Receipt of this character causes the next character to be taken literally.
748 Special character on input and is recognized if the
751 Receipt of this character toggles the flushing of terminal output.
753 Special character on input and is recognized if the
756 Receipt of this character causes a
758 signal to be sent to the foreground process group of the
763 causes the kernel to write a status message to the terminal
764 that displays the current load average, the name of the
765 command in the foreground, its process ID, the symbolic
766 wait channel, the number of user and system seconds used,
767 the percentage of cpu the process is getting, and the resident
768 set size of the process.
775 characters cannot be changed.
776 The values for all the remaining characters can be set and are
777 described later in the document under
778 Special Control Characters.
781 character functions associated with changeable special control characters
782 can be disabled individually by setting their value to
783 .Dv {_POSIX_VDISABLE} ;
785 .Sx "Special Control Characters" .
787 If two or more special characters have the same value, the function
788 performed when that character is received is undefined.
790 If a modem disconnect is detected by the terminal interface for a
791 controlling terminal, and if
798 signal is sent to the controlling
799 process associated with the terminal.
800 Unless other arrangements have
801 been made, this causes the controlling process to terminate.
802 Any subsequent call to the
804 function returns the value zero,
805 indicating end of file.
806 Thus, processes that read a terminal
807 file and test for end-of-file can terminate appropriately after a
811 .\" condition specified in 6.1.1.4 that applies
812 .\" when the implementation supports job control also exists, it is
813 .\" unspecified whether the
821 to the terminal device returns -1, with
825 until the device is closed.
826 .Sh General Terminal Interface
827 .Ss Closing a Terminal Device File
828 The last process to close a terminal device file causes any output
829 to be sent to the device and any input to be discarded.
832 is set in the control modes, and the communications port supports a
833 disconnect function, the terminal device performs a disconnect.
834 .Ss Parameters That Can Be Set
835 Routines that need to control certain terminal
838 do so by using the termios structure as defined in the header
840 This structure contains minimally four scalar elements of bit flags
841 and one array of special characters.
842 The scalar flag elements are named:
848 The character array is named
850 and its maximum index is
855 field describe the basic
856 terminal input control, and are composed of
859 .Bl -tag -width IMAXBEL -offset indent -compact
861 /* ignore BREAK condition */
863 /* map BREAK to SIGINTR */
865 /* ignore (discard) parity errors */
867 /* mark parity and framing errors */
869 /* enable checking of parity errors */
871 /* strip 8th bit off chars */
877 /* map CR to NL (ala CRMOD) */
879 /* enable output flow control */
881 /* enable input flow control */
883 /* any char will restart after stop */
885 /* ring bell on input queue full */
888 In the context of asynchronous serial data transmission, a break
889 condition is defined as a sequence of zero-valued bits that continues for
890 more than the time to send one byte.
891 The entire sequence of zero-valued
892 bits is interpreted as a single break condition, even if it continues for
893 a time equivalent to more than one byte.
894 In contexts other than
895 asynchronous serial data transmission the definition of a break condition
896 is implementation defined.
900 is set, a break condition detected on input is ignored, that
901 is, not put on the input queue and therefore not read by any process.
906 is set, the break condition flushes the
907 input and output queues and if the terminal is the controlling terminal
908 of a foreground process group, the break condition generates a
911 signal to that foreground process group.
916 is set, a break condition is read as a single
927 is set, a byte with a framing or parity error (other than
934 is not set, a byte with a framing or parity
935 error (other than break) is given to the application as the
936 three-character sequence
943 flag preceding each sequence and X is the data of the character received
945 To avoid ambiguity in this case, if
950 is given to the application as
958 is set, a framing or parity error (other than
959 break) is given to the application as a single character
964 is set, input parity checking is enabled.
968 input parity checking is disabled, allowing output parity generation
969 without input parity errors.
970 Note that whether input parity checking is
971 enabled or disabled is independent of whether parity detection is enabled
973 .Sx "Control Modes" ) .
974 If parity detection is enabled but input
975 parity checking is disabled, the hardware to which the terminal is
976 connected recognizes the parity bit, but the terminal special file
977 does not check whether this bit is set correctly or not.
981 is set, valid input bytes are first stripped to seven bits,
982 otherwise all eight bits are processed.
988 character is translated into a
995 character is ignored (not
1010 is set, start/stop output control is enabled.
1013 character suspends output and a received
1019 is also set, then any character may
1028 read, but merely perform flow control functions.
1036 characters are read.
1040 is set, start/stop input control is enabled.
1041 The system shall transmit one or more
1043 characters, which are intended to cause the
1044 terminal device to stop transmitting data, as needed to prevent the input
1045 queue from overflowing and causing the undefined behavior described in
1046 .Sx "Input Processing and Reading Data" ,
1047 and shall transmit one or more
1049 characters, which are
1050 intended to cause the terminal device to resume transmitting data, as
1051 soon as the device can continue transmitting data without risk of
1052 overflowing the input queue.
1053 The precise conditions under which
1057 characters are transmitted are implementation defined.
1061 is set and the input queue is full, subsequent input shall cause an
1064 character to be transmitted to
1067 The initial input control value after
1069 is implementation defined.
1073 field describe the basic terminal output control,
1074 and are composed of the following masks:
1076 .Bl -tag -width ONOEOT -offset indent -compact
1078 /* enable following output processing */
1080 /* map NL to CR-NL (ala
1086 /* tab delay mask */
1088 /* no tab delay and expansion */
1090 /* expand tabs to spaces */
1097 /* do not transmit CRs on column 0 */
1099 /* on the terminal NL performs the CR function */
1104 is set, the remaining flag masks are interpreted as follows;
1105 otherwise characters are transmitted without change.
1109 is set, newlines are translated to carriage return, linefeeds.
1113 is set, carriage returns are translated to newlines.
1117 bits specify the tab delay.
1122 and compared with the
1129 is set, tabs are expanded to the appropriate number of
1130 spaces (assuming 8 column tab stops).
1137 are discarded on output.
1141 is set, no CR character is transmitted when at column 0 (first position).
1145 is set, the NL character is assumed to do the carriage-return function;
1146 the column pointer will be set to 0.
1150 field describe the basic
1151 terminal hardware control, and are composed of the
1154 specified are supported by all hardware.
1156 .Bl -tag -width CRTSXIFLOW -offset indent -compact
1158 /* character size mask */
1160 /* 5 bits (pseudo) */
1168 /* send 2 stop bits */
1170 /* enable receiver */
1174 /* odd parity, else even */
1176 /* hang up on last close */
1178 /* ignore modem status lines */
1182 flow control of output */
1188 /* RTS flow control of input */
1190 /* flow control output via Carrier */
1195 bits specify the byte size in bits for both transmission and
1201 and compared with the
1208 This size does not include the parity bit, if any.
1211 is set, two stop bits are used, otherwise one stop bit.
1212 For example, at 110 baud, two stop bits are normally used.
1216 is set, the receiver is enabled.
1217 Otherwise, no character is received.
1218 Not all hardware supports this bit.
1219 In fact, this flag is pretty silly and if it were not part of the
1222 it would be omitted.
1226 is set, parity generation and detection are enabled and a parity
1227 bit is added to each character.
1228 If parity is enabled,
1231 odd parity if set, otherwise even parity is used.
1235 is set, the modem control lines for the port are lowered
1236 when the last process with the port open closes the port or the process
1238 The modem connection is broken.
1242 is set, a connection does not depend on the state of the modem
1246 is clear, the modem status lines are
1249 Under normal circumstances, a call to the
1252 the modem connection to complete.
1261 immediately without waiting for the connection.
1266 flag is currently unused.
1270 is set then output flow control is controlled by the state
1273 If the object for which the control modes are set is not an asynchronous
1274 serial connection, some of the modes may be ignored; for example, if an
1275 attempt is made to set the baud rate on a network connection to a
1276 terminal on another host, the baud rate may or may not be set on the
1277 connection between that terminal and the machine it is directly connected
1282 field describe the control of
1283 various functions, and are composed of the following
1286 .Bl -tag -width NOKERNINFO -offset indent -compact
1288 /* visual erase for line kill */
1290 /* visually erase chars */
1292 /* enable echoing */
1300 /* visual erase mode for hardcopy */
1302 /* echo control chars as ^(Char) */
1310 /* canonicalize input lines */
1322 /* external processing */
1324 /* stop background jobs from output */
1326 /* output being flushed (state) */
1328 /* no kernel output from
1332 /* XXX retype pending input (state) */
1334 /* don't flush after interrupt */
1339 is set, input characters are echoed back to the terminal.
1342 is not set, input characters are not echoed.
1350 character causes the terminal
1351 to erase the last character in the current line from the display, if
1353 If there is no character to erase, an implementation may echo
1354 an indication that this was the case or do nothing.
1363 the current line to be discarded and the system echoes the
1376 the current line to be discarded and the system causes
1378 to erase the line from the display.
1384 are set, the system assumes
1385 that the display is a printing device and prints a
1386 backslash and the erased characters when processing
1388 characters, followed by a forward slash.
1392 is set, the system echoes control characters
1393 in a visible fashion using a caret followed by the control character.
1397 is set, the system uses an alternative algorithm
1398 for determining what constitutes a word when processing
1409 character echoes even if
1415 is set, canonical processing is enabled.
1417 erase and kill edit functions, and the assembly of input characters into
1424 .Sx "Canonical Mode Input Processing" .
1428 is not set, read requests are satisfied directly from the input
1430 A read is not satisfied until at least
1433 received or the timeout value
1435 expired between bytes.
1437 represents tenths of seconds.
1439 .Sx "Noncanonical Mode Input Processing"
1444 is set, each input character is checked against the special
1452 character matches one of these control characters, the function
1453 associated with that character is performed.
1458 Thus these special input functions are possible only
1465 is set, implementation-defined functions are recognized
1466 from the input data.
1476 is implementation defined.
1480 implementation-defined functions are not recognized, and the
1481 corresponding input characters are not processed as described for
1490 is set, the normal flush of the input and output queues
1503 is sent to the process group of a process that tries to write to
1504 its controlling terminal if it is not in the foreground process group for
1506 This signal, by default, stops the members of the process group.
1507 Otherwise, the output generated by that process is output to the
1508 current output stream.
1509 Processes that are blocking or ignoring
1511 signals are excepted and allowed to produce output and the
1518 is set, the kernel does not produce a status message
1523 .Ss Special Control Characters
1524 The special control characters values are defined by the array
1526 This table lists the array index, the corresponding special character,
1527 and the system default value.
1528 For an accurate list of
1529 the system defaults, consult the header file
1530 .In sys/ttydefaults.h .
1532 .Bl -column "Index Name" "Special Character" -offset indent -compact
1533 .It Em "Index Name Special Character Default Value"
1534 .It Dv VEOF Ta EOF Ta \&^D
1535 .It Dv VEOL Ta EOL Ta _POSIX_VDISABLE
1536 .It Dv VEOL2 Ta EOL2 Ta _POSIX_VDISABLE
1537 .It Dv VERASE Ta ERASE Ta \&^? Ql \&\e177
1538 .It Dv VWERASE Ta WERASE Ta \&^W
1539 .It Dv VKILL Ta KILL Ta \&^U
1540 .It Dv VREPRINT Ta REPRINT Ta \&^R
1541 .It Dv VINTR Ta INTR Ta \&^C
1542 .It Dv VQUIT Ta QUIT Ta \&^\e\e Ql \&\e34
1543 .It Dv VSUSP Ta SUSP Ta \&^Z
1544 .It Dv VDSUSP Ta DSUSP Ta \&^Y
1545 .It Dv VSTART Ta START Ta \&^Q
1546 .It Dv VSTOP Ta STOP Ta \&^S
1547 .It Dv VLNEXT Ta LNEXT Ta \&^V
1548 .It Dv VDISCARD Ta DISCARD Ta \&^O
1549 .It Dv VMIN Ta --- Ta \&1
1550 .It Dv VTIME Ta --- Ta \&0
1551 .It Dv VSTATUS Ta STATUS Ta \&^T
1555 value of one of the changeable special control characters (see
1556 .Sx "Special Characters" )
1558 .Dv {_POSIX_VDISABLE} ,
1559 that function is disabled; that is, no input
1560 data is recognized as the disabled special character.
1564 not set, the value of
1565 .Dv {_POSIX_VDISABLE}
1566 has no special meaning for the
1574 The initial values of the flags and control characters
1578 the values in the header
1579 .In sys/ttydefaults.h .