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
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14 .\" This product includes software developed by the University of
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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
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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
33 .\" $FreeBSD: src/share/man/man4/termios.4,v 1.12.2.9 2001/12/17 11:30:12 ru Exp $
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. For most hardware, the presence
49 of a connection is indicated by the assertion of the hardware
52 If the termios structure associated with the terminal file has the
54 flag set in the cflag, or if the
59 call, then the open will succeed even without
60 a connection being present.
61 In practice, applications
62 seldom open these files; they are opened by special programs, such
68 an application's standard input, output, and error files.
69 .Ss Job Control in a Nutshell
70 Every process is associated with a particular process group and session.
71 The grouping is hierarchical: every member of a particular process group is a
72 member of the same session. This structuring is used in managing groups
73 of related processes for purposes of
74 .\" .Gw "job control" ;
77 ability from the keyboard (or from program control) to simultaneously
79 a complex command (a command composed of one or more related
80 processes). The grouping into process groups allows delivering
81 of signals that stop or start the group as a whole, along with
82 arbitrating which process group has access to the single controlling
83 terminal. The grouping at a higher layer into sessions is to restrict
84 the job control related signals and system calls to within processes
85 resulting from a particular instance of a "login". Typically, a session
86 is created when a user logs in, and the login terminal is setup
87 to be the controlling terminal; all processes spawned from that
88 login shell are in the same session, and inherit the controlling
92 operating interactively (that is, reading commands from a terminal)
93 normally groups related processes together by placing them into the
94 same process group. A set of processes in the same process group
95 is collectively referred to as a "job". When the foreground process
96 group of the terminal is the same as the process group of a particular
97 job, that job is said to be in the "foreground". When the process
98 group of the terminal is different from the process group of
99 a job (but is still the controlling terminal), that job is said
100 to be in the "background". Normally the
101 shell reads a command and starts the job that implements that
102 command. If the command is to be started in the foreground (typical), it
103 sets the process group of the terminal to the process group
104 of the started job, waits for the job to complete, and then
105 sets the process group of the terminal back to its own process
106 group (it puts itself into the foreground). If the job is to
107 be started in the background (as denoted by the shell operator "&"),
108 it never changes the process group of the terminal and doesn't
109 wait for the job to complete (that is, it immediately attempts to read the next
110 command). If the job is started in the foreground, the user may
113 which generates the terminal stop signal
115 and has the effect of stopping the entire job.
116 The shell will notice that the job stopped, and will resume running after
117 placing itself in the foreground.
118 The shell also has commands for placing stopped jobs in the background,
119 and for placing stopped or background jobs into the foreground.
120 .Ss Orphaned Process Groups
121 An orphaned process group is a process group that has no process
122 whose parent is in a different process group, yet is in the same
123 session. Conceptually it means a process group that doesn't have
124 a parent that could do anything if it were to be stopped. For example,
125 the initial login shell is typically in an orphaned process group.
126 Orphaned process groups are immune to keyboard generated stop
127 signals and job control signals resulting from reads or writes to the
128 controlling terminal.
129 .Ss The Controlling Terminal
130 A terminal may belong to a process as its controlling terminal. Each
131 process of a session that has a controlling terminal has the same
132 controlling terminal. A terminal may be the controlling terminal for at
133 most one session. The controlling terminal for a session is allocated by
134 the session leader by issuing the
136 ioctl. A controlling terminal
137 is never acquired by merely opening a terminal device file.
138 When a controlling terminal becomes
139 associated with a session, its foreground process group is set to
140 the process group of the session leader.
142 The controlling terminal is inherited by a child process during a
144 function call. A process relinquishes its controlling terminal when it
145 creates a new session with the
147 function; other processes
148 remaining in the old session that had this terminal as their controlling
149 terminal continue to have it.
150 A process does not relinquish its
151 controlling terminal simply by closing all of its file descriptors
152 associated with the controlling terminal if other processes continue to
155 When a controlling process terminates, the controlling terminal is
156 disassociated from the current session, allowing it to be acquired by a
157 new session leader. Subsequent access to the terminal by other processes
158 in the earlier session will be denied, with attempts to access the
159 terminal treated as if modem disconnect had been sensed.
160 .Ss Terminal Access Control
161 If a process is in the foreground process group of its controlling
162 terminal, read operations are allowed.
163 Any attempts by a process
164 in a background process group to read from its controlling terminal
170 following special cases apply: If the reading process is ignoring or
173 signal, or if the process group of the reading
174 process is orphaned, the
181 signal is sent. The default action of the
183 signal is to stop the
184 process to which it is sent.
186 If a process is in the foreground process group of its controlling
187 terminal, write operations are allowed.
188 Attempts by a process in a background process group to write to its
189 controlling terminal will cause the process group to be sent a
191 signal unless one of the following special cases apply: If
196 is set and the process is ignoring or blocking the
198 signal, the process is allowed to write to the terminal and the
200 signal is not sent. If
202 is set, and the process group of
203 the writing process is orphaned, and the writing process is not ignoring
212 and no signal is sent.
214 Certain calls that set terminal parameters are treated in the same
215 fashion as write, except that
217 is ignored; that is, the effect is
218 identical to that of terminal writes when
221 .Ss Input Processing and Reading Data
222 A terminal device associated with a terminal device file may operate in
223 full-duplex mode, so that data may arrive even while output is occurring.
224 Each terminal device file has associated with it an input queue, into
225 which incoming data is stored by the system before being read by a
226 process. The system imposes a limit,
227 .Pf \&{ Dv MAX_INPUT Ns \&} ,
229 bytes that may be stored in the input queue. The behavior of the system
230 when this limit is exceeded depends on the setting of the
234 If this flag is set, the terminal
238 character each time a character is received
239 while the input queue is full. Otherwise, the input queue is flushed
240 upon receiving the character.
242 Two general kinds of input processing are available, determined by
243 whether the terminal device file is in canonical mode or noncanonical
246 input characters are processed according to the
250 fields. Such processing can include echoing, which
251 in general means transmitting input characters immediately back to the
252 terminal when they are received from the terminal. This is useful for
253 terminals that can operate in full-duplex mode.
255 The manner in which data is provided to a process reading from a terminal
256 device file is dependent on whether the terminal device file is in
257 canonical or noncanonical mode.
259 Another dependency is whether the
267 flag is clear, then the read request is
268 blocked until data is available or a signal has been received. If the
270 flag is set, then the read request is completed, without
271 blocking, in one of three ways:
272 .Bl -enum -offset indent
274 If there is enough data available to satisfy the entire request,
275 and the read completes successfully the number of
276 bytes read is returned.
278 If there is not enough data available to satisfy the entire
279 request, and the read completes successfully, having read as
280 much data as possible, the number of bytes read is returned.
282 If there is no data available, the read returns -1, with
288 When data is available depends on whether the input processing mode is
289 canonical or noncanonical.
290 .Ss Canonical Mode Input Processing
291 In canonical mode input processing, terminal input is processed in units
292 of lines. A line is delimited by a newline
294 character, an end-of-file
296 character, or an end-of-line
299 .Sx "Special Characters"
305 This means that a read request will
306 not return until an entire line has been typed, or a signal has been
307 received. Also, no matter how many bytes are requested in the read call,
308 at most one line is returned. It is not, however, necessary to
309 read a whole line at once; any number of bytes, even one, may be
310 requested in a read without losing information.
312 .Pf \&{ Dv MAX_CANON Ns \&}
314 number of bytes in a line.
315 The behavior of the system when this limit is
316 exceeded is the same as when the input queue limit
317 .Pf \&{ Dv MAX_INPUT Ns \&} ,
320 Erase and kill processing occur when either of two special characters,
326 .Sx "Special Characters"
327 section), is received.
328 This processing affects data in the input queue that has not yet been
329 delimited by a newline
334 character. This un-delimited
335 data makes up the current line. The
337 character deletes the last
338 character in the current line, if there is any. The
341 deletes all data in the current line, if there is any. The
345 characters have no effect if there is no data in the current line.
350 characters themselves are not placed in the input
352 .Ss Noncanonical Mode Input Processing
353 In noncanonical mode input processing, input bytes are not assembled into
354 lines, and erase and kill processing does not occur. The values of the
360 array are used to determine how to
361 process the bytes received.
364 represents the minimum number of bytes that should be received when
367 function successfully returns.
369 is a timer of 0.1 second
370 granularity that is used to time out bursty and short term data
374 .Dv \&{ Dv MAX_INPUT Ns \&} ,
376 request is undefined. The four possible values for
381 their interactions are described below.
382 .Ss "Case A: MIN > 0, TIME > 0"
385 serves as an inter-byte timer and is activated after
386 the first byte is received. Since it is an inter-byte timer, it is reset
387 after a byte is received. The interaction between
392 follows: as soon as one byte is received, the inter-byte timer is
395 bytes are received before the inter-byte timer expires
396 (remember that the timer is reset upon receipt of each byte), the read is
397 satisfied. If the timer expires before
399 bytes are received, the
400 characters received to that point are returned to the user. Note that if
402 expires at least one byte is returned because the timer would
403 not have been enabled unless a byte was received. In this case
407 > 0) the read blocks until the
412 activated by the receipt of the first byte, or a signal is received. If
413 data is in the buffer at the time of the
416 if data had been received immediately after the
418 .Ss "Case B: MIN > 0, TIME = 0"
419 In this case, since the value of
421 is zero, the timer plays no role
424 is significant. A pending read is not satisfied until
426 bytes are received (i.e., the pending read blocks until
429 are received), or a signal is received. A program that uses this case to
430 read record-based terminal
432 may block indefinitely in the read
434 .Ss "Case C: MIN = 0, TIME > 0"
439 no longer represents an inter-byte
440 timer. It now serves as a read timer that is activated as soon as the
441 read function is processed. A read is satisfied as soon as a single
442 byte is received or the read timer expires. Note that in this case if
443 the timer expires, no bytes are returned. If the timer does not
444 expire, the only way the read can be satisfied is if a byte is received.
445 In this case the read will not block indefinitely waiting for a byte; if
446 no byte is received within
448 seconds after the read is initiated,
449 the read returns a value of zero, having read no data. If data is
450 in the buffer at the time of the read, the timer is started as if
451 data had been received immediately after the read.
452 .Ss Case D: MIN = 0, TIME = 0
453 The minimum of either the number of bytes requested or the number of
454 bytes currently available is returned without waiting for more
455 bytes to be input. If no characters are available, read returns a
456 value of zero, having read no data.
457 .Ss Writing Data and Output Processing
458 When a process writes one or more bytes to a terminal device file, they
459 are processed according to the
464 implementation may provide a buffering mechanism; as such, when a call to
466 completes, all of the bytes written have been scheduled for
467 transmission to the device, but the transmission will not necessarily
469 .\" See also .Sx "6.4.2" for the effects of
472 .Ss Special Characters
473 Certain characters have special functions on input or output or both.
474 These functions are summarized as follows:
475 .Bl -tag -width indent
477 Special character on input and is recognized if the
481 section) is enabled. Generates a
483 signal which is sent to all processes in the foreground
484 process group for which the terminal is the controlling
490 discarded when processed.
492 Special character on input and is recognized if the
494 flag is enabled. Generates a
497 sent to all processes in the foreground process group
498 for which the terminal is the controlling terminal. If
502 character is discarded when
505 Special character on input and is recognized if the
507 flag is set. Erases the last character in the
509 .Sx "Canonical Mode Input Processing" .
510 It does not erase beyond
511 the start of a line, as delimited by an
521 discarded when processed.
523 Special character on input and is recognized if the
525 flag is set. Deletes the entire line, as
535 character is discarded when processed.
537 Special character on input and is recognized if the
539 flag is set. When received, all the bytes
540 waiting to be read are immediately passed to the
541 process, without waiting for a newline, and the
543 is discarded. Thus, if there are no bytes waiting (that
546 occurred at the beginning of a line), a byte
547 count of zero is returned from the
549 representing an end-of-file indication. If
554 character is discarded when processed.
556 Special character on input and is recognized if the
558 flag is set. It is the line delimiter
561 Special character on input and is recognized if the
563 flag is set. Is an additional line delimiter,
569 flag is enabled, receipt of the
573 signal to be sent to all processes in the
574 foreground process group for which the terminal is the
575 controlling terminal, and the
578 discarded when processed.
580 Special character on both input and output and is
586 control) flag is set. Can be used to temporarily
587 suspend output. It is useful with fast terminals to
588 prevent output from disappearing before it can be read.
593 character is discarded when
596 Special character on both input and output and is
602 control) flag is set. Can be used to resume output that
603 has been suspended by a
609 character is discarded when processed.
611 Special character on input and is recognized if the
613 flag is set; it is the
623 is not set, this character is translated into a
626 has the same effect as a
631 The following special characters are extensions defined by this
632 system and are not a part of
635 .Bl -tag -width indent
639 character. Same function as
642 Special character on input and is recognized if the
644 flag is set. Erases the last word in the current
645 line according to one of two algorithms. If the
647 flag is not set, first any preceding whitespace is
648 erased, and then the maximal sequence of non-whitespace
651 is set, first any preceding
652 whitespace is erased, and then the maximal sequence
653 of alphabetic/underscores or non alphabetic/underscores.
654 As a special case in this second algorithm, the first previous
655 non-whitespace character is skipped in determining
656 whether the preceding word is a sequence of
657 alphabetic/underscores. This sounds confusing but turns
658 out to be quite practical.
660 Special character on input and is recognized if the
662 flag is set. Causes the current input edit line
665 Has similar actions to the
667 character, except that
670 signal is delivered when one of the processes
671 in the foreground process group issues a
674 controlling terminal.
676 Special character on input and is recognized if the
678 flag is set. Receipt of this character causes the next
679 character to be taken literally.
681 Special character on input and is recognized if the
683 flag is set. Receipt of this character toggles the flushing
686 Special character on input and is recognized if the
688 flag is set. Receipt of this character causes a
690 signal to be sent to the foreground process group of the
691 terminal. Also, if the
694 causes the kernel to write a status message to the terminal
695 that displays the current load average, the name of the
696 command in the foreground, its process ID, the symbolic
697 wait channel, the number of user and system seconds used,
698 the percentage of cpu the process is getting, and the resident
699 set size of the process.
706 characters cannot be changed.
707 The values for all the remaining characters can be set and are
708 described later in the document under
709 Special Control Characters.
712 character functions associated with changeable special control characters
713 can be disabled individually by setting their value to
714 .Dv {_POSIX_VDISABLE} ;
716 .Sx "Special Control Characters" .
718 If two or more special characters have the same value, the function
719 performed when that character is received is undefined.
721 If a modem disconnect is detected by the terminal interface for a
722 controlling terminal, and if
729 signal is sent to the controlling
730 process associated with the terminal. Unless other arrangements have
731 been made, this causes the controlling process to terminate.
732 Any subsequent call to the
734 function returns the value zero,
735 indicating end of file. Thus, processes that read a terminal
736 file and test for end-of-file can terminate appropriately after a
740 .\" condition specified in 6.1.1.4 that applies
741 .\" when the implementation supports job control also exists, it is
742 .\" unspecified whether the
750 to the terminal device returns -1, with
754 until the device is closed.
755 .Sh General Terminal Interface
756 .Ss Closing a Terminal Device File
757 The last process to close a terminal device file causes any output
758 to be sent to the device and any input to be discarded. Then, if
760 is set in the control modes, and the communications port supports a
761 disconnect function, the terminal device performs a disconnect.
762 .Ss Parameters That Can Be Set
763 Routines that need to control certain terminal
766 do so by using the termios structure as defined in the header
768 This structure contains minimally four scalar elements of bit flags
769 and one array of special characters. The scalar flag elements are
776 The character array is named
778 and its maximum index is
783 field describe the basic
784 terminal input control, and are composed of
787 .Bl -tag -width IMAXBEL -offset indent -compact
789 /* ignore BREAK condition */
791 /* map BREAK to SIGINTR */
793 /* ignore (discard) parity errors */
795 /* mark parity and framing errors */
797 /* enable checking of parity errors */
799 /* strip 8th bit off chars */
805 /* map CR to NL (ala CRMOD) */
807 /* enable output flow control */
809 /* enable input flow control */
811 /* any char will restart after stop */
813 /* ring bell on input queue full */
816 In the context of asynchronous serial data transmission, a break
817 condition is defined as a sequence of zero-valued bits that continues for
818 more than the time to send one byte. The entire sequence of zero-valued
819 bits is interpreted as a single break condition, even if it continues for
820 a time equivalent to more than one byte. In contexts other than
821 asynchronous serial data transmission the definition of a break condition
822 is implementation defined.
826 is set, a break condition detected on input is ignored, that
827 is, not put on the input queue and therefore not read by any process. If
831 is set, the break condition flushes the
832 input and output queues and if the terminal is the controlling terminal
833 of a foreground process group, the break condition generates a
836 signal to that foreground process group. If neither
840 is set, a break condition is read as a single
851 is set, a byte with a framing or parity error (other than
858 is not set, a byte with a framing or parity
859 error (other than break) is given to the application as the
860 three-character sequence
867 flag preceding each sequence and X is the data of the character received
868 in error. To avoid ambiguity in this case, if
873 is given to the application as
881 is set, a framing or parity error (other than
882 break) is given to the application as a single character
887 is set, input parity checking is enabled. If
890 input parity checking is disabled, allowing output parity generation
891 without input parity errors. Note that whether input parity checking is
892 enabled or disabled is independent of whether parity detection is enabled
894 .Sx "Control Modes" ) .
895 If parity detection is enabled but input
896 parity checking is disabled, the hardware to which the terminal is
897 connected recognizes the parity bit, but the terminal special file
898 does not check whether this bit is set correctly or not.
902 is set, valid input bytes are first stripped to seven bits,
903 otherwise all eight bits are processed.
909 character is translated into a
915 character is ignored (not
929 is set, start/stop output control is enabled. A received
931 character suspends output and a received
937 is also set, then any character may
946 read, but merely perform flow control functions. When
957 is set, start/stop input control is enabled. The system shall
960 characters, which are intended to cause the
961 terminal device to stop transmitting data, as needed to prevent the input
962 queue from overflowing and causing the undefined behavior described in
963 .Sx "Input Processing and Reading Data" ,
964 and shall transmit one or more
966 characters, which are
967 intended to cause the terminal device to resume transmitting data, as
968 soon as the device can continue transmitting data without risk of
969 overflowing the input queue. The precise conditions under which
973 characters are transmitted are implementation defined.
977 is set and the input queue is full, subsequent input shall cause an
980 character to be transmitted to
983 The initial input control value after
985 is implementation defined.
989 field describe the basic terminal output control,
990 and are composed of the following masks:
992 .Bl -tag -width OXTABS -offset indent -compact
994 /* enable following output processing */
996 /* map NL to CR-NL (ala
1002 /* expand tabs to spaces */
1009 /* do not transmit CRs on column 0 */
1011 /* on the termianl NL performs the CR function */
1016 is set, the remaining flag masks are interpreted as follows;
1017 otherwise characters are transmitted without change.
1021 is set, newlines are translated to carriage return, linefeeds.
1025 is set, carriage returns are translated to newlines.
1029 is set, tabs are expanded to the appropriate number of
1030 spaces (assuming 8 column tab stops).
1037 are discarded on output.
1041 is set, no CR character is transmitted when at column 0 (first position).
1045 is set, the NL character is assumed to do the carriage-return function;
1046 the column pointer will be set to 0.
1050 field describe the basic
1051 terminal hardware control, and are composed of the
1054 specified are supported by all hardware.
1056 .Bl -tag -width CRTSXIFLOW -offset indent -compact
1058 /* character size mask */
1060 /* 5 bits (pseudo) */
1068 /* send 2 stop bits */
1070 /* enable receiver */
1074 /* odd parity, else even */
1076 /* hang up on last close */
1078 /* ignore modem status lines */
1082 flow control of output */
1088 /* RTS flow control of input */
1090 /* flow control output via Carrier */
1095 bits specify the byte size in bits for both transmission and
1100 and compared with the
1107 This size does not include the parity bit, if any. If
1109 is set, two stop bits are used, otherwise one stop bit. For example, at
1110 110 baud, two stop bits are normally used.
1114 is set, the receiver is enabled. Otherwise, no character is
1116 Not all hardware supports this bit. In fact, this flag
1117 is pretty silly and if it were not part of the
1120 it would be omitted.
1124 is set, parity generation and detection are enabled and a parity
1125 bit is added to each character. If parity is enabled,
1128 odd parity if set, otherwise even parity is used.
1132 is set, the modem control lines for the port are lowered
1133 when the last process with the port open closes the port or the process
1134 terminates. The modem connection is broken.
1138 is set, a connection does not depend on the state of the modem
1141 is clear, the modem status lines are
1144 Under normal circumstances, a call to the
1147 the modem connection to complete. However, if the
1155 immediately without waiting for the connection.
1160 flag is currently unused.
1164 is set then output flow control is controlled by the state
1167 If the object for which the control modes are set is not an asynchronous
1168 serial connection, some of the modes may be ignored; for example, if an
1169 attempt is made to set the baud rate on a network connection to a
1170 terminal on another host, the baud rate may or may not be set on the
1171 connection between that terminal and the machine it is directly connected
1176 field describe the control of
1177 various functions, and are composed of the following
1180 .Bl -tag -width NOKERNINFO -offset indent -compact
1182 /* visual erase for line kill */
1184 /* visually erase chars */
1186 /* enable echoing */
1194 /* visual erase mode for hardcopy */
1196 /* echo control chars as ^(Char) */
1204 /* canonicalize input lines */
1216 /* external processing */
1218 /* stop background jobs from output */
1220 /* output being flushed (state) */
1222 /* no kernel output from
1226 /* XXX retype pending input (state) */
1228 /* don't flush after interrupt */
1233 is set, input characters are echoed back to the terminal. If
1235 is not set, input characters are not echoed.
1243 character causes the terminal
1244 to erase the last character in the current line from the display, if
1245 possible. If there is no character to erase, an implementation may echo
1246 an indication that this was the case or do nothing.
1255 the current line to be discarded and the system echoes the
1268 the current line to be discarded and the system causes
1270 to erase the line from the display.
1276 are set, the system assumes
1277 that the display is a printing device and prints a
1278 backslash and the erased characters when processing
1280 characters, followed by a forward slash.
1284 is set, the system echoes control characters
1285 in a visible fashion using a caret followed by the control character.
1289 is set, the system uses an alternative algorithm
1290 for determining what constitutes a word when processing
1301 character echoes even if
1307 is set, canonical processing is enabled. This enables the
1308 erase and kill edit functions, and the assembly of input characters into
1315 .Sx "Canonical Mode Input Processing" .
1319 is not set, read requests are satisfied directly from the input
1320 queue. A read is not satisfied until at least
1323 received or the timeout value
1325 expired between bytes. The time value
1326 represents tenths of seconds. See
1327 .Sx "Noncanonical Mode Input Processing"
1332 is set, each input character is checked against the special
1338 (job control only). If an input
1339 character matches one of these control characters, the function
1340 associated with that character is performed. If
1343 checking is done. Thus these special input functions are possible only
1350 is set, implementation-defined functions are recognized
1351 from the input data. How
1360 is implementation defined.
1364 implementation-defined functions are not recognized, and the
1365 corresponding input characters are not processed as described for
1374 is set, the normal flush of the input and output queues
1387 is sent to the process group of a process that tries to write to
1388 its controlling terminal if it is not in the foreground process group for
1389 that terminal. This signal, by default, stops the members of the process
1390 group. Otherwise, the output generated by that process is output to the
1391 current output stream. Processes that are blocking or ignoring
1393 signals are excepted and allowed to produce output and the
1400 is set, the kernel does not produce a status message
1405 .Ss Special Control Characters
1406 The special control characters values are defined by the array
1408 This table lists the array index, the corresponding special character,
1409 and the system default value. For an accurate list of
1410 the system defaults, consult the header file
1411 .In sys/ttydefaults.h .
1413 .Bl -column "Index Name" "Special Character" -offset indent -compact
1414 .It Em "Index Name Special Character Default Value"
1415 .It Dv VEOF Ta EOF Ta \&^D
1416 .It Dv VEOL Ta EOL Ta _POSIX_VDISABLE
1417 .It Dv VEOL2 Ta EOL2 Ta _POSIX_VDISABLE
1418 .It Dv VERASE Ta ERASE Ta \&^? Ql \&\e177
1419 .It Dv VWERASE Ta WERASE Ta \&^W
1420 .It Dv VKILL Ta KILL Ta \&^U
1421 .It Dv VREPRINT Ta REPRINT Ta \&^R
1422 .It Dv VINTR Ta INTR Ta \&^C
1423 .It Dv VQUIT Ta QUIT Ta \&^\e\e Ql \&\e34
1424 .It Dv VSUSP Ta SUSP Ta \&^Z
1425 .It Dv VDSUSP Ta DSUSP Ta \&^Y
1426 .It Dv VSTART Ta START Ta \&^Q
1427 .It Dv VSTOP Ta STOP Ta \&^S
1428 .It Dv VLNEXT Ta LNEXT Ta \&^V
1429 .It Dv VDISCARD Ta DISCARD Ta \&^O
1430 .It Dv VMIN Ta --- Ta \&1
1431 .It Dv VTIME Ta --- Ta \&0
1432 .It Dv VSTATUS Ta STATUS Ta \&^T
1436 value of one of the changeable special control characters (see
1437 .Sx "Special Characters" )
1439 .Dv {_POSIX_VDISABLE} ,
1440 that function is disabled; that is, no input
1441 data is recognized as the disabled special character.
1445 not set, the value of
1446 .Dv {_POSIX_VDISABLE}
1447 has no special meaning for the
1455 The initial values of the flags and control characters
1459 the values in the header
1460 .In sys/ttydefaults.h .