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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 $
34 .\" $DragonFly: src/share/man/man4/termios.4,v 1.2 2003/06/17 04:36:59 dillon Exp $
41 .Nd general terminal line discipline
45 This describes a general terminal line discipline that is
46 supported on tty asynchronous communication ports.
47 .Ss Opening a Terminal Device File
48 When a terminal file is opened, it normally causes the process to wait
49 until a connection is established. 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. This structuring is used in managing groups
74 of related processes for purposes of
75 .\" .Gw "job control" ;
78 ability from the keyboard (or from program control) to simultaneously
80 a complex command (a command composed of one or more related
81 processes). The grouping into process groups allows delivering
82 of signals that stop or start the group as a whole, along with
83 arbitrating which process group has access to the single controlling
84 terminal. The grouping at a higher layer into sessions is to restrict
85 the job control related signals and system calls to within processes
86 resulting from a particular instance of a "login". Typically, a session
87 is created when a user logs in, and the login terminal is setup
88 to be the controlling terminal; all processes spawned from that
89 login shell are in the same session, and inherit the controlling
93 operating interactively (that is, reading commands from a terminal)
94 normally groups related processes together by placing them into the
95 same process group. A set of processes in the same process group
96 is collectively referred to as a "job". When the foreground process
97 group of the terminal is the same as the process group of a particular
98 job, that job is said to be in the "foreground". When the process
99 group of the terminal is different from the process group of
100 a job (but is still the controlling terminal), that job is said
101 to be in the "background". Normally the
102 shell reads a command and starts the job that implements that
103 command. If the command is to be started in the foreground (typical), it
104 sets the process group of the terminal to the process group
105 of the started job, waits for the job to complete, and then
106 sets the process group of the terminal back to its own process
107 group (it puts itself into the foreground). If the job is to
108 be started in the background (as denoted by the shell operator "&"),
109 it never changes the process group of the terminal and doesn't
110 wait for the job to complete (that is, it immediately attempts to read the next
111 command). If the job is started in the foreground, the user may
114 which generates the terminal stop signal
116 and has the effect of stopping the entire job.
117 The shell will notice that the job stopped, and will resume running after
118 placing itself in the foreground.
119 The shell also has commands for placing stopped jobs in the background,
120 and for placing stopped or background jobs into the foreground.
121 .Ss Orphaned Process Groups
122 An orphaned process group is a process group that has no process
123 whose parent is in a different process group, yet is in the same
124 session. Conceptually it means a process group that doesn't have
125 a parent that could do anything if it were to be stopped. For example,
126 the initial login shell is typically in an orphaned process group.
127 Orphaned process groups are immune to keyboard generated stop
128 signals and job control signals resulting from reads or writes to the
129 controlling terminal.
130 .Ss The Controlling Terminal
131 A terminal may belong to a process as its controlling terminal. Each
132 process of a session that has a controlling terminal has the same
133 controlling terminal. A terminal may be the controlling terminal for at
134 most one session. The controlling terminal for a session is allocated by
135 the session leader by issuing the
137 ioctl. A controlling terminal
138 is never acquired by merely opening a terminal device file.
139 When a controlling terminal becomes
140 associated with a session, its foreground process group is set to
141 the process group of the session leader.
143 The controlling terminal is inherited by a child process during a
145 function call. A process relinquishes its controlling terminal when it
146 creates a new session with the
148 function; other processes
149 remaining in the old session that had this terminal as their controlling
150 terminal continue to have it.
151 A process does not relinquish its
152 controlling terminal simply by closing all of its file descriptors
153 associated with the controlling terminal if other processes continue to
156 When a controlling process terminates, the controlling terminal is
157 disassociated from the current session, allowing it to be acquired by a
158 new session leader. Subsequent access to the terminal by other processes
159 in the earlier session will be denied, with attempts to access the
160 terminal treated as if modem disconnect had been sensed.
161 .Ss Terminal Access Control
162 If a process is in the foreground process group of its controlling
163 terminal, read operations are allowed.
164 Any attempts by a process
165 in a background process group to read from its controlling terminal
171 following special cases apply: If the reading process is ignoring or
174 signal, or if the process group of the reading
175 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
211 and no signal is sent.
213 Certain calls that set terminal parameters are treated in the same
214 fashion as write, except that
216 is ignored; that is, the effect is
217 identical to that of terminal writes when
220 .Ss Input Processing and Reading Data
221 A terminal device associated with a terminal device file may operate in
222 full-duplex mode, so that data may arrive even while output is occurring.
223 Each terminal device file has associated with it an input queue, into
224 which incoming data is stored by the system before being read by a
225 process. The system imposes a limit,
226 .Pf \&{ Dv MAX_INPUT Ns \&} ,
228 bytes that may be stored in the input queue. The behavior of the system
229 when this limit is exceeded depends on the setting of the
233 If this flag is set, the terminal
237 character each time a character is received
238 while the input queue is full. Otherwise, the input queue is flushed
239 upon receiving the character.
241 Two general kinds of input processing are available, determined by
242 whether the terminal device file is in canonical mode or noncanonical
245 input characters are processed according to the
249 fields. Such processing can include echoing, which
250 in general means transmitting input characters immediately back to the
251 terminal when they are received from the terminal. This is useful for
252 terminals that can operate in full-duplex mode.
254 The manner in which data is provided to a process reading from a terminal
255 device file is dependent on whether the terminal device file is in
256 canonical or noncanonical mode.
258 Another dependency is whether the
266 flag is clear, then the read request is
267 blocked until data is available or a signal has been received. If the
269 flag is set, then the read request is completed, without
270 blocking, in one of three ways:
271 .Bl -enum -offset indent
273 If there is enough data available to satisfy the entire request,
274 and the read completes successfully the number of
275 bytes read is returned.
277 If there is not enough data available to satisfy the entire
278 request, and the read completes successfully, having read as
279 much data as possible, the number of bytes read is returned.
281 If there is no data available, the read returns -1, with
286 When data is available depends on whether the input processing mode is
287 canonical or noncanonical.
288 .Ss Canonical Mode Input Processing
289 In canonical mode input processing, terminal input is processed in units
290 of lines. A line is delimited by a newline
292 character, an end-of-file
294 character, or an end-of-line
297 .Sx "Special Characters"
303 This means that a read request will
304 not return until an entire line has been typed, or a signal has been
305 received. Also, no matter how many bytes are requested in the read call,
306 at most one line is returned. It is not, however, necessary to
307 read a whole line at once; any number of bytes, even one, may be
308 requested in a read without losing information.
310 .Pf \&{ Dv MAX_CANON Ns \&}
312 number of bytes in a line.
313 The behavior of the system when this limit is
314 exceeded is the same as when the input queue limit
315 .Pf \&{ Dv MAX_INPUT Ns \&} ,
318 Erase and kill processing occur when either of two special characters,
324 .Sx "Special Characters section" ) ,
326 This processing affects data in the input queue that has not yet been
327 delimited by a newline
332 character. This un-delimited
333 data makes up the current line. The
335 character deletes the last
336 character in the current line, if there is any. The
339 deletes all data in the current line, if there is any. The
343 characters have no effect if there is no data in the current line.
348 characters themselves are not placed in the input
350 .Ss Noncanonical Mode Input Processing
351 In noncanonical mode input processing, input bytes are not assembled into
352 lines, and erase and kill processing does not occur. The values of the
358 array are used to determine how to
359 process the bytes received.
362 represents the minimum number of bytes that should be received when
365 function successfully returns.
367 is a timer of 0.1 second
368 granularity that is used to time out bursty and short term data
372 .Dv \&{ Dv MAX_INPUT Ns \&} ,
374 request is undefined. The four possible values for
379 their interactions are described below.
380 .Ss "Case A: MIN > 0, TIME > 0"
383 serves as an inter-byte timer and is activated after
384 the first byte is received. Since it is an inter-byte timer, it is reset
385 after a byte is received. The interaction between
390 follows: as soon as one byte is received, the inter-byte timer is
393 bytes are received before the inter-byte timer expires
394 (remember that the timer is reset upon receipt of each byte), the read is
395 satisfied. If the timer expires before
397 bytes are received, the
398 characters received to that point are returned to the user. Note that if
400 expires at least one byte is returned because the timer would
401 not have been enabled unless a byte was received. In this case
405 > 0) the read blocks until the
410 activated by the receipt of the first byte, or a signal is received. If
411 data is in the buffer at the time of the
414 if data had been received immediately after the
416 .Ss "Case B: MIN > 0, TIME = 0"
417 In this case, since the value of
419 is zero, the timer plays no role
422 is significant. A pending read is not satisfied until
424 bytes are received (i.e., the pending read blocks until
427 are received), or a signal is received. A program that uses this case to
428 read record-based terminal
430 may block indefinitely in the read
432 .Ss "Case C: MIN = 0, TIME > 0"
437 no longer represents an inter-byte
438 timer. It now serves as a read timer that is activated as soon as the
439 read function is processed. A read is satisfied as soon as a single
440 byte is received or the read timer expires. Note that in this case if
441 the timer expires, no bytes are returned. If the timer does not
442 expire, the only way the read can be satisfied is if a byte is received.
443 In this case the read will not block indefinitely waiting for a byte; if
444 no byte is received within
446 seconds after the read is initiated,
447 the read returns a value of zero, having read no data. If data is
448 in the buffer at the time of the read, the timer is started as if
449 data had been received immediately after the read.
450 .Ss Case D: MIN = 0, TIME = 0
451 The minimum of either the number of bytes requested or the number of
452 bytes currently available is returned without waiting for more
453 bytes to be input. If no characters are available, read returns a
454 value of zero, having read no data.
455 .Ss Writing Data and Output Processing
456 When a process writes one or more bytes to a terminal device file, they
457 are processed according to the
462 implementation may provide a buffering mechanism; as such, when a call to
464 completes, all of the bytes written have been scheduled for
465 transmission to the device, but the transmission will not necessarily
467 .\" See also .Sx "6.4.2" for the effects of
470 .Ss Special Characters
471 Certain characters have special functions on input or output or both.
472 These functions are summarized as follows:
473 .Bl -tag -width indent
475 Special character on input and is recognized if the
479 section) is enabled. Generates a
481 signal which is sent to all processes in the foreground
482 process group for which the terminal is the controlling
488 discarded when processed.
490 Special character on input and is recognized if the
492 flag is enabled. Generates a
495 sent to all processes in the foreground process group
496 for which the terminal is the controlling terminal. If
500 character is discarded when
503 Special character on input and is recognized if the
505 flag is set. Erases the last character in the
507 .Sx "Canonical Mode Input Processing" .
508 It does not erase beyond
509 the start of a line, as delimited by an
519 discarded when processed.
521 Special character on input and is recognized if the
523 flag is set. Deletes the entire line, as
533 character is discarded when processed.
535 Special character on input and is recognized if the
537 flag is set. When received, all the bytes
538 waiting to be read are immediately passed to the
539 process, without waiting for a newline, and the
541 is discarded. Thus, if there are no bytes waiting (that
544 occurred at the beginning of a line), a byte
545 count of zero is returned from the
547 representing an end-of-file indication. If
552 character is discarded when processed.
554 Special character on input and is recognized if the
556 flag is set. It is the line delimiter
559 Special character on input and is recognized if the
561 flag is set. Is an additional line delimiter,
567 flag is enabled, receipt of the
571 signal to be sent to all processes in the
572 foreground process group for which the terminal is the
573 controlling terminal, and the
576 discarded when processed.
578 Special character on both input and output and is
584 control) flag is set. Can be used to temporarily
585 suspend output. It is useful with fast terminals to
586 prevent output from disappearing before it can be read.
591 character is discarded when
594 Special character on both input and output and is
600 control) flag is set. Can be used to resume output that
601 has been suspended by a
607 character is discarded when processed.
609 Special character on input and is recognized if the
611 flag is set; it is the
621 is not set, this character is translated into a
624 has the same effect as a
629 The following special characters are extensions defined by this
630 system and are not a part of
633 .Bl -tag -width indent
637 character. Same function as
640 Special character on input and is recognized if the
642 flag is set. Erases the last word in the current
643 line according to one of two algorithms. If the
645 flag is not set, first any preceding whitespace is
646 erased, and then the maximal sequence of non-whitespace
649 is set, first any preceding
650 whitespace is erased, and then the maximal sequence
651 of alphabetic/underscores or non alphabetic/underscores.
652 As a special case in this second algorithm, the first previous
653 non-whitespace character is skipped in determining
654 whether the preceding word is a sequence of
655 alphabetic/underscores. This sounds confusing but turns
656 out to be quite practical.
658 Special character on input and is recognized if the
660 flag is set. Causes the current input edit line
663 Has similar actions to the
665 character, except that
668 signal is delivered when one of the processes
669 in the foreground process group issues a
672 controlling terminal.
674 Special character on input and is recognized if the
676 flag is set. Receipt of this character causes the next
677 character to be taken literally.
679 Special character on input and is recognized if the
681 flag is set. Receipt of this character toggles the flushing
684 Special character on input and is recognized if the
686 flag is set. Receipt of this character causes a
688 signal to be sent to the foreground process group of the
689 terminal. Also, if the
692 causes the kernel to write a status message to the terminal
693 that displays the current load average, the name of the
694 command in the foreground, its process ID, the symbolic
695 wait channel, the number of user and system seconds used,
696 the percentage of cpu the process is getting, and the resident
697 set size of the process.
704 characters cannot be changed.
705 The values for all the remaining characters can be set and are
706 described later in the document under
707 Special Control Characters.
710 character functions associated with changeable special control characters
711 can be disabled individually by setting their value to
712 .Dv {_POSIX_VDISABLE} ;
714 .Sx "Special Control Characters" .
716 If two or more special characters have the same value, the function
717 performed when that character is received is undefined.
719 If a modem disconnect is detected by the terminal interface for a
720 controlling terminal, and if
727 signal is sent to the controlling
728 process associated with the terminal. Unless other arrangements have
729 been made, this causes the controlling process to terminate.
730 Any subsequent call to the
732 function returns the value zero,
733 indicating end of file. Thus, processes that read a terminal
734 file and test for end-of-file can terminate appropriately after a
738 .\" condition specified in 6.1.1.4 that applies
739 .\" when the implementation supports job control also exists, it is
740 .\" unspecified whether the
748 to the terminal device returns -1, with
752 until the device is closed.
753 .Sh General Terminal Interface
754 .Ss Closing a Terminal Device File
755 The last process to close a terminal device file causes any output
756 to be sent to the device and any input to be discarded. Then, if
758 is set in the control modes, and the communications port supports a
759 disconnect function, the terminal device performs a disconnect.
760 .Ss Parameters That Can Be Set
761 Routines that need to control certain terminal
764 do so by using the termios structure as defined in the header
766 This structure contains minimally four scalar elements of bit flags
767 and one array of special characters. The scalar flag elements are
774 The character array is named
776 and its maximum index is
781 field describe the basic
782 terminal input control, and are composed of
785 .Bl -tag -width IMAXBEL -offset indent -compact
787 /* ignore BREAK condition */
789 /* map BREAK to SIGINTR */
791 /* ignore (discard) parity errors */
793 /* mark parity and framing errors */
795 /* enable checking of parity errors */
797 /* strip 8th bit off chars */
803 /* map CR to NL (ala CRMOD) */
805 /* enable output flow control */
807 /* enable input flow control */
809 /* any char will restart after stop */
811 /* ring bell on input queue full */
814 In the context of asynchronous serial data transmission, a break
815 condition is defined as a sequence of zero-valued bits that continues for
816 more than the time to send one byte. The entire sequence of zero-valued
817 bits is interpreted as a single break condition, even if it continues for
818 a time equivalent to more than one byte. In contexts other than
819 asynchronous serial data transmission the definition of a break condition
820 is implementation defined.
824 is set, a break condition detected on input is ignored, that
825 is, not put on the input queue and therefore not read by any process. If
829 is set, the break condition flushes the
830 input and output queues and if the terminal is the controlling terminal
831 of a foreground process group, the break condition generates a
834 signal to that foreground process group. If neither
838 is set, a break condition is read as a single
849 is set, a byte with a framing or parity error (other than
856 is not set, a byte with a framing or parity
857 error (other than break) is given to the application as the
858 three-character sequence
865 flag preceding each sequence and X is the data of the character received
866 in error. To avoid ambiguity in this case, if
871 is given to the application as
879 is set, a framing or parity error (other than
880 break) is given to the application as a single character
885 is set, input parity checking is enabled. If
888 input parity checking is disabled, allowing output parity generation
889 without input parity errors. Note that whether input parity checking is
890 enabled or disabled is independent of whether parity detection is enabled
892 .Sx "Control Modes" ) .
893 If parity detection is enabled but input
894 parity checking is disabled, the hardware to which the terminal is
895 connected recognizes the parity bit, but the terminal special file
896 does not check whether this bit is set correctly or not.
900 is set, valid input bytes are first stripped to seven bits,
901 otherwise all eight bits are processed.
907 character is translated into a
913 character is ignored (not
927 is set, start/stop output control is enabled. A received
929 character suspends output and a received
935 is also set, then any character may
944 read, but merely perform flow control functions. When
955 is set, start/stop input control is enabled. The system shall
958 characters, which are intended to cause the
959 terminal device to stop transmitting data, as needed to prevent the input
960 queue from overflowing and causing the undefined behavior described in
961 .Sx "Input Processing and Reading Data" ,
962 and shall transmit one or more
964 characters, which are
965 intended to cause the terminal device to resume transmitting data, as
966 soon as the device can continue transmitting data without risk of
967 overflowing the input queue. The precise conditions under which
971 characters are transmitted are implementation defined.
975 is set and the input queue is full, subsequent input shall cause an
978 character to be transmitted to
981 The initial input control value after
983 is implementation defined.
987 field describe the basic terminal output control,
988 and are composed of the following masks:
990 .Bl -tag -width OXTABS -offset indent -compact
992 /* enable following output processing */
994 /* map NL to CR-NL (ala
1000 /* expand tabs to spaces */
1007 /* do not transmit CRs on column 0 */
1009 /* on the termianl NL performs the CR function */
1014 is set, the remaining flag masks are interpreted as follows;
1015 otherwise characters are transmitted without change.
1019 is set, newlines are translated to carriage return, linefeeds.
1023 is set, carriage returns are translated to newlines.
1027 is set, tabs are expanded to the appropriate number of
1028 spaces (assuming 8 column tab stops).
1035 are discarded on output.
1039 is set, no CR character is transmitted when at column 0 (first position).
1043 is set, the NL character is assumed to do the carriage-return function;
1044 the column pointer will be set to 0.
1048 field describe the basic
1049 terminal hardware control, and are composed of the
1052 specified are supported by all hardware.
1054 .Bl -tag -width CRTSXIFLOW -offset indent -compact
1056 /* character size mask */
1058 /* 5 bits (pseudo) */
1066 /* send 2 stop bits */
1068 /* enable receiver */
1072 /* odd parity, else even */
1074 /* hang up on last close */
1076 /* ignore modem status lines */
1080 flow control of output */
1086 /* RTS flow control of input */
1088 /* flow control output via Carrier */
1093 bits specify the byte size in bits for both transmission and
1098 and compared with the
1105 This size does not include the parity bit, if any. If
1107 is set, two stop bits are used, otherwise one stop bit. For example, at
1108 110 baud, two stop bits are normally used.
1112 is set, the receiver is enabled. Otherwise, no character is
1114 Not all hardware supports this bit. In fact, this flag
1115 is pretty silly and if it were not part of the
1118 it would be omitted.
1122 is set, parity generation and detection are enabled and a parity
1123 bit is added to each character. If parity is enabled,
1126 odd parity if set, otherwise even parity is used.
1130 is set, the modem control lines for the port are lowered
1131 when the last process with the port open closes the port or the process
1132 terminates. The modem connection is broken.
1136 is set, a connection does not depend on the state of the modem
1139 is clear, the modem status lines are
1142 Under normal circumstances, a call to the
1145 the modem connection to complete. However, if the
1153 immediately without waiting for the connection.
1158 flag is currently unused.
1162 is set then output flow control is controlled by the state
1165 If the object for which the control modes are set is not an asynchronous
1166 serial connection, some of the modes may be ignored; for example, if an
1167 attempt is made to set the baud rate on a network connection to a
1168 terminal on another host, the baud rate may or may not be set on the
1169 connection between that terminal and the machine it is directly connected
1174 field describe the control of
1175 various functions, and are composed of the following
1178 .Bl -tag -width NOKERNINFO -offset indent -compact
1180 /* visual erase for line kill */
1182 /* visually erase chars */
1184 /* enable echoing */
1192 /* visual erase mode for hardcopy */
1194 /* echo control chars as ^(Char) */
1202 /* canonicalize input lines */
1214 /* external processing */
1216 /* stop background jobs from output */
1218 /* output being flushed (state) */
1220 /* no kernel output from
1224 /* XXX retype pending input (state) */
1226 /* don't flush after interrupt */
1231 is set, input characters are echoed back to the terminal. If
1233 is not set, input characters are not echoed.
1241 character causes the terminal
1242 to erase the last character in the current line from the display, if
1243 possible. If there is no character to erase, an implementation may echo
1244 an indication that this was the case or do nothing.
1253 the current line to be discarded and the system echoes the
1266 the current line to be discarded and the system causes
1268 to erase the line from the display.
1274 are set, the system assumes
1275 that the display is a printing device and prints a
1276 backslash and the erased characters when processing
1278 characters, followed by a forward slash.
1282 is set, the system echoes control characters
1283 in a visible fashion using a caret followed by the control character.
1287 is set, the system uses an alternative algorithm
1288 for determining what constitutes a word when processing
1299 character echoes even if
1305 is set, canonical processing is enabled. This enables the
1306 erase and kill edit functions, and the assembly of input characters into
1313 .Sx "Canonical Mode Input Processing" .
1317 is not set, read requests are satisfied directly from the input
1318 queue. A read is not satisfied until at least
1321 received or the timeout value
1323 expired between bytes. The time value
1324 represents tenths of seconds. See
1325 .Sx "Noncanonical Mode Input Processing"
1330 is set, each input character is checked against the special
1336 (job control only). If an input
1337 character matches one of these control characters, the function
1338 associated with that character is performed. If
1341 checking is done. Thus these special input functions are possible only
1348 is set, implementation-defined functions are recognized
1349 from the input data. How
1358 is implementation defined.
1362 implementation-defined functions are not recognized, and the
1363 corresponding input characters are not processed as described for
1372 is set, the normal flush of the input and output queues
1385 is sent to the process group of a process that tries to write to
1386 its controlling terminal if it is not in the foreground process group for
1387 that terminal. This signal, by default, stops the members of the process
1388 group. Otherwise, the output generated by that process is output to the
1389 current output stream. Processes that are blocking or ignoring
1391 signals are excepted and allowed to produce output and the
1398 is set, the kernel does not produce a status message
1403 .Ss Special Control Characters
1404 The special control characters values are defined by the array
1406 This table lists the array index, the corresponding special character,
1407 and the system default value. For an accurate list of
1408 the system defaults, consult the header file
1409 .Aq Pa ttydefaults.h .
1411 .Bl -column "Index Name" "Special Character" -offset indent -compact
1412 .It Em "Index Name Special Character Default Value"
1413 .It Dv VEOF Ta EOF Ta \&^D
1414 .It Dv VEOL Ta EOL Ta _POSIX_VDISABLE
1415 .It Dv VEOL2 Ta EOL2 Ta _POSIX_VDISABLE
1416 .It Dv VERASE Ta ERASE Ta \&^? Ql \&\e177
1417 .It Dv VWERASE Ta WERASE Ta \&^W
1418 .It Dv VKILL Ta KILL Ta \&^U
1419 .It Dv VREPRINT Ta REPRINT Ta \&^R
1420 .It Dv VINTR Ta INTR Ta \&^C
1421 .It Dv VQUIT Ta QUIT Ta \&^\e\e Ql \&\e34
1422 .It Dv VSUSP Ta SUSP Ta \&^Z
1423 .It Dv VDSUSP Ta DSUSP Ta \&^Y
1424 .It Dv VSTART Ta START Ta \&^Q
1425 .It Dv VSTOP Ta STOP Ta \&^S
1426 .It Dv VLNEXT Ta LNEXT Ta \&^V
1427 .It Dv VDISCARD Ta DISCARD Ta \&^O
1428 .It Dv VMIN Ta --- Ta \&1
1429 .It Dv VTIME Ta --- Ta \&0
1430 .It Dv VSTATUS Ta STATUS Ta \&^T
1434 value of one of the changeable special control characters (see
1435 .Sx "Special Characters" )
1437 .Dv {_POSIX_VDISABLE} ,
1438 that function is disabled; that is, no input
1439 data is recognized as the disabled special character.
1443 not set, the value of
1444 .Dv {_POSIX_VDISABLE}
1445 has no special meaning for the
1453 The initial values of the flags and control characters
1457 the values in the header
1458 .Aq Pa sys/ttydefaults.h .